Galvanic Hydrogenation Reaction in Metal Oxide

doi:10.21203/rs.3.rs-3998371/v1

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Galvanic Hydrogenation Reaction in Metal Oxide

https://doi.org/10.21203/rs.3.rs-3998371/v1

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Rational reforming of metal oxide has a potential importance to modulate their inherent properties toward appealing characteristics for various applications. Here, we present a detailed fundamental study of the proton migration phenomena between mediums and propose the methodology for an exquisitely controllable metal oxide hydrogenation through galvanic reactions with metallic cation under ambient atmosphere. As a proof of concept for hydrogenation, we study the role of proton adoption on the structural properties of molybdenum trioxide, as a representative, and its impact on redox characteristics in Li-ion battery (LiB) systems using electrochemical experiments and first-principles calculation. The proton adoption contributes to a lattice rearrangement facilitating the faster Li-ion diffusion along the selected layered and mediates the diffusion pathway that promote the enhancements of high rate performance and cyclic stability. Our work provides great physicochemical insights of hydrogenations and underscores the viable approach for improving the redox characteristics of layered oxide materials.

Physical sciences/Materials science/Materials for energy and catalysis/Corrosion

Physical sciences/Materials science/Materials for energy and catalysis/Batteries

Physical sciences/Materials science/Condensed-matter physics/Electronic properties and materials

In the research field of materials engineering, hydrogenating is one of the promising methods to manipulate the electrical and redox characteristics of metal oxides towards the favorable features for diverse applications^1-5. The rearrangements of the crystal lattice with the deviation of metal atoms from their equivalent states have enormous impacts on the dielectric properties and energy states of electron of metal oxide during proton insertion, and therefore, a lot of effort has been devoted to tunable hydrogenation for these purposes. Moreover, inspired by proton migration into the oxides, there has been significant interest in oxide hydrogenation as a feasible strategy of hydrogen energy transportation for upcoming hydrogen economy^6-8. Furthermore, recent studies have emphasized the vital role of H-binding energy of supported oxides to enhance the catalytic activities of primary catalyst in electrolysis and photo-electrochemical systems^9-13.

It has long been known that proton doping significantly impacts the inherent characteristics of metal oxide^13,14. Therefore, the elucidation of the proton diffusion phenomenon from a hydrogen-rich atmosphere to the surface of hydrogen-poor metal oxides is important for further developments. To address this challenge, many efforts have been devoted to revealing this behavior. Experiments have verified that the sacrificial metals that have lower work functions accelerate the transfer of electron-proton pairs into the oxide lattice, motivating work on tunable oxide hydrogenation using sacrificial solid metal^4,5,15,16. With respect to the hydrogenating phenomena itself, an exploration of proton movements using first-principles calculation revealed that the negatively charged oxide surface, driven by electron accumulation, contributes to lower energy barriers for proton migration^15,16. Moreover, it has been confirmed that the proton capable metal oxide exhibits various phase conditions depending on a degree of the hydrogenation^17,18, unlocking the great opportunity of tunable hydrogenated oxide and selectivity for favorable features.

However, it is worth mentioning that the question about natural forces governing the hydrogenation of the metal oxides has not been fully elucidated. Specifically, there are no significant clues or criteria to correlate hydrogenation origins with the degree of hydrogenation and the crystallographic order of lattice oxide. Undeniably, there have been many practical achievements, however, previous hydrogenation studies are often neglect to consider the regularity of various crystal phases, obscuring the conception of oxide hydrogenation. That is, due to the lack of the cornerstone correlating the fundamental origins and material characteristics, consistent explanations of the natural force covering the proton movement are overlooked; and therefore, the sole descriptor for the impact of H-binding on physicochemical characteristics of metal oxide still remained elusive.

In this context, we present a detailed study of the oxide hydrogenation by devising a novel cation-solution treatment method for controllable hydrogenation in metal oxides. The basis of the original hypothesis was that the impetus of hydrogenation is likely to be associated with the equivalent electrochemical potentials difference between cation as a reducing agent and metal oxide. We attributed the proton migratory phenomena to the mixed potential-induced electrochemical galvanic reaction, which occurs at the interfaces of solid oxide and dissolved cations, accompanying with the proton migration from the acid reservoir, as depicted in Fig. 1a. Moreover, to reveal the sole impact of H-binding on inherent electrochemistry of metal oxide, we have studied the electrochemistry of orthorhombic molybdenum trioxide (α-MoO₃), one of the layered oxides having accommodatable sites for protons, and its hydrogenated state having identical orthorhombic crystal. In particular, the redox behavior was investigated in organic electrolyte based-lithium ion battery (LiB) system, which is a suitable platform for understanding the inserted proton effects while precluding proton intervention from the electrolyte. Remarkably, the redox characteristics of hydrogenated α-MoO₃ (H-MoO₃) in LiB systems were verified to be totally determined by means of the proton doping along with the enhancements of high rate performance and cyclic stability. Typically, it is found that there was no capacity limitation for partially reduced H-MoO₃ in spite of the lower oxidation state of molybdenum at the expense of partial reduction with cation dopant. To elucidate this contradictory question, the completely distinguishable redox natures of H-MoO₃ were demonstrated by computational density functional theory (DFT) and the nudged elastic band (NEB) approach. It is especially worthy noticing that proton adoption and its impacts on an intermolecular interaction contribute to the advent of the new sites and pathway for lithium-ion diffusion.

Methodologies of galvanic redox reaction inducing metal oxide hydrogenations.

Figure 1a illustrates a novel cation-solution treatment method that we designed for controllable hydrogenation in metal oxides. The linear sweep voltammetry (LSV) curves (Fig. 1b and Fig. S1a) indicate two distinct reductive potentials of 0.44 and 0.15 V_SHE, respectively: first reduction peak corresponds to the proton and charge transport to α-MoO₃ (H_xMoO₃, x < 0.4), and the second peak indicates an additional reduction reaction for proton storage with phase transition into monoclinic phase (H_yMoO₃, y > 0.4) ^17,18. The basic electrochemistry of the α-MoO₃ capacitive nature provides notable feature of oxide hydrogenation; and we focused here on the possibility of tunable hydrogenation strategy via galvanic reaction using specific ionic reductants having proper standard potential.

To demonstrate that the mixed potential-induced galvanic reaction is the determinant of electron-proton pair migration, we studied the feasibility of Mo(Ⅳ) cation solution as hydrogenation trigger. The cyclic voltammetry (CV) analysis of Pt electrode under Mo(Ⅳ) solution, as shown in Fig. 1c and Fig. S1b, clearly shows that the oxidation current (for MoO²⁺(Ⅳ) + H₂O → MoO₂⁺ (Ⅴ) + 2H⁺ + 2e⁻) occurs at around 0.30 V_SHE, which is in agreement with the Pourbaix diagram for molybdenum¹⁹. As a proof of concept for electrochemical galvanic reaction, we organized the standard potentials of various molybdenum oxide phases corresponding to the degree of hydrogenation (MoO₃/H_xMoO₃/H_yMoO₃), and that of cations (Mo(Ⅳ) and V(Ⅱ)), and solid Cu metal as well to reconsider the conventional solid-metal treatments method in the electrochemical point of view as shown in Fig. 1d. Firstly, we used dark-brownish Mo(Ⅳ) cation solution as reductant (the detailed explanation for MoO₃ modification method is described in Material preparation section and Fig. S2). The prepared hydrogenated α-MoO₃ using specific Mo(Ⅳ) concentration shows the two distinct reflection (XRD) patterns (Fig. 2a); major reflection peaks of pristine α-MoO₃ shift to lower angles by means of hydrogenation, representing a widened van der Waals (vdW) inter-layer gaps from 14.0 to 14.4 Å. Additionally, the X-ray photoelectron spectroscopy (XPS) analysis confirmed that Mo⁵⁺ species in Mo 3d spectra (Fig. 2b) gradually and selectively increases with the occurrence of the surface adsorbed species corresponding to –OH in O 1s spectra (Fig. 2c) accompanying with chemical shifts of lattice oxygen to lower binding energy. A stoichiometry of H-MoO₃, calculated by area ratio of Mo⁵⁺ and Mo⁶⁺ in Mo 3d spectra (Fig. 2b), is determined to be H_0.392MoO₃, which agrees with the electrochemical results for H-doped α-MoO₃ (H_xMoO₃, x < 0.4). Whereas, in case of cation-solution treatments using violet-colored V(Ⅱ) solution as hydrogenation trigger, whose reduction potential value (V(Ⅲ)/V(Ⅱ), -0.255 V_SHE²⁰) is lower than that of H_yMoO₃/H_xMoO₃ (x < 0.4 < y, 0.15 V_SHE), the V(Ⅱ) cation treated α-MoO₃ shows the monoclinic phase as shown in Fig. S3. In this case, XPS results show a varying oxidation state in Mo 3d spectra with increased surface absorbed species (Fig. S4), implying the presences of an additional redox reaction with proton insertion compared with the Mo(Ⅳ) treated case (H_xMoO₃, x = 0.392). We also examined the feasibility of cation-treatment methods using commercial WO₃ (c-WO₃, monoclinic), whose reduction potential for WO₃/H_xWO₃ is lower than 0.3 V_SHE²¹, and verify the identical trend of oxide hydrogenation (Figs. S5 and S6). In this regard, metal oxide hydrogenation strategy using solid state metal also could be accepted since the reduction potential of Cu metal (Cu/Cu²⁺, 0.34 V_SHE, Fig. 1d) is lower than that of molybdenum oxide (MoO₃/H_xMoO₃, 0.44 V_SHE) even though this method requires for extra efforts to eliminate the solid metal residual. Hereby, these results provide the reasonable deduction to unveil the clues of the hydrogenation origins. Hence, considering the restrictive crystal phase and the basic electrochemistry of proton capable oxide in acidic condition by means of hydrogenation degree, oxide hydrogenation could be driven spontaneously by galvanic reaction via cation-solution treatment; namely, the primary keystone of controllable oxide hydrogenation determining the extent of proton doping and crystal phases is the standard potential differences between oxide material and metallic cation.

The next question in our study was oriented toward the physicochemical properties of H-MoO₃ since there was no significant variation in morphology, crystallographic plane, and atomic vibrational Raman spectra as shown in Figs. S7 and S8. Thereby, it is the optimum conditions to investigate the sole impact of H-binding. Whereas, contrary to crystallographic analysis results, Fig. 2d shows the distinct features in FTIR vibration signals of H-MoO₃, especially the absence of stretching vibration frequency corresponding to the Mo-O_a (asymmetric oxygen) bond represented at 827.4 and 819.0 cm^− 1. Instead, a noticeable peak at 627.4 cm^− 1 is observed after proton doping. We used DFT calculation to estimate the stabilized H-sites of H-MoO₃ (Fig. S9), through which it is found that intersectional asymmetric oxygen sites are the energetically favorable for proton dangling as depicted in Fig. 2e. Notably, it is extraordinary feature of proton doped α-MoO₃ since cation doping strategies with large dopant radius are typical approaches to increase the vdW gaps via pre-intercalation in inter-layer spaces. Considering the relative radius of cations including Li⁺ (0.90 Å), Na⁺ (1.16 Å), and K⁺ (1.52 Å) or molecule such as H₂O (vdW radius, 1.70 Å) ^22–24, it is reasonable to consider that these dopants would be incorporated in vdW layer (14.0 Å for pristine MoO₃) surrounded by terminal oxygen rather than inner-plane sites. In contrast, protons, having the lowest occupation of 0.87 × 10^− 5 Å, are more likely to be located at neighboring lattice oxygen atoms of octahedral MoO₆ (Fig. 2e). Thus, the triggers of the noticeable lattice distortion are entirely distinguishable, raising a different perspective of varying characteristic of metal oxide by means of dopant types and sites.

Electrochemical properties of H-doped orthorhombic MoO ₃.

To elucidate the effects of the H-binding on electrochemical characteristics of α-MoO₃, electrochemical analyses in LiB systems for pristine MoO₃ and H-MoO₃ (H_xMoO₃, x = 0.392) were conducted as shown in Fig. 3. Specifically, the orthorhombic structure of α-MoO₃ takes an accommodatable sites for Li-ion; inner-plane (intra-layer site) of MoO₆ adjacent with O_a and O_s, (symmetric oxygen) and inter-plane (inter-layer site) of vdW gaps neighboring O_t (terminal oxygen) lattices of MoO₃ (Fig. 2e) ²⁵. However, there is a pervasive problem of irreversible phase transition reaction at pristine state of α-MoO₃ shown in reduction peaks for Li-ion intercalation at 2.70 vs. Li/Li⁺ (Fig. S10a) ^24,25. In contrast, the initial CV curve for H-MoO₃ indicates a suppressed current plateau around 2.70 V vs. Li/Li⁺ and an obvious reduction peak at 2.38 V vs. Li/Li⁺ as shown in Fig. S10b. For further clarification on this irreversibility, ex-situ XRD analysis of (de)lithiated electrodes were conducted. In Fig. S11, ambiguous XRD patterns are observed for both lithiated MoO₃ and H-MoO₃, whereas, completely different results are seen following delithiation. There are uncertain diffraction peaks as a result of the irreversible phase transition for delithiated MoO₃ during the initial cycle; in contrast, H-MoO₃ shows the well-maintained crystallographic order of orthorhombic structure. It is remarkable that Mo-O_a bonding changes with lattice rearrangements would prohibit the irreversible Li-ion intercalation at the intra-layer sites of MoO₆.

After the 2nd activation cycle, H-MoO₃ achieves a reversible specific capacity of 1009.4 C g^− 1 (280.4 mAh g^− 1) at 0.1 mV s^− 1, which is higher than the capacity realized for pristine MoO₃ (946.8 C g^− 1, 263 mAh g^− 1) and close to the theoretical capacity (1005 C g^− 1, 279 mAh g^− 1) ²⁵, as shown in Fig. 3a. Notably, it exhibits an additional pair of redox potential at 2.95 and 2.68 V vs. Li/Li⁺ for H-MoO₃, and that is in stark contrast to the original redox characteristics in a whole range of high scan rates as shown in Fig. 3b. Besides, in quantitative capacitive analysis of the Li-ion intercalation behaviors, the b-value corresponding to major lithiation of pristine MoO₃ was 0.71, whereas that of H-MoO₃ was 0.88 as shown in Fig. 3c, representing the enhanced pseudo-capacitive like Li-ion diffusion features by the proton introduction^26,27 (detailed instructions for correlation between sweep rate, redox peak current density, and b-value as the indicator of capacitive ion diffusion are described in Fig. S12). Similarly, log (ʋ) versus log (i) plot for anodic peak current (Fig. S12d) also indicates the enhanced capacitive Li-ion diffusion features of H-MoO₃. This series of enhanced capacitive characteristics are also represented by enhanced rate capability shown in Fig. 3d. Typically, at the current of 1.0 A g^− 1, H-MoO₃ achieved a stable specific capacity of 170.8 mAh g^− 1, while pristine MoO₃ has 136.0 mAh g^− 1 with a small decline in capacity. Thereafter, as shown in Fig. 3e, pristine MoO₃ shows the rapid capacity decaying early in the cycling process, capacity decrease to 84.1 mAh g^− 1 after 250 cycles, whereas, H-MoO₃ shows the remarkably enhanced cycling stability, exhibiting 84.7% (144.3 mAh g^− 1) and 72.1% (122.9 mAh g^− 1) of capacitance retention at 1.0 A g^− 1 during 500 and 1,000 cycles, respectively.

We further take interest in the existence of multiple redox peaks, and especially in an enhanced capability of H-MoO₃. An intuitive advantage of the H-binding introduction has been known as band-gap tuning by advent of H-doping level^28,29, which could be confirmed by our DOS calculations (Fig. S13). Then, to elucidate the redox characteristics, the formation energies for lithiated state of both pristine MoO₃ and H-MoO₃ were calculated. The pristine state retains the two accommodatable sites for Li-ion (inter/intra site) having formation energy of -2.023/-1.648 eV (Fig. 4a, Fig. S14); as discussed, however, due to the irreversible lithiation at the intra-layer site during initial discharge process, the redox peak of pristine state shows the one reversible major peak corresponding to the lithiation at the inter-layer sites. Whereas, since the H-MoO₃ exhibits the asymmetrical distribution of proton insertion as a consequence of limited proton adoption (Fig. 2e), the formation energies for inter and intra-layer sites are divided into two groups as shown in Fig. 4b (Fig. S15, * marks imply the lithiation sites derived from the lattice asymmetry): that is, the asymmetric lattice order induced by limited hydrogenation would result in differences of formation energy and distinctive redox potential (Fig. 3a). Moreover, first-principle calculation results in Fig. S15 indicate that the proton adoption sites are distinguished from the Li-ion accommodatable sites, through which it is confirmed that H-binding of H-MoO₃ would have less influences on preservable Li-ion sites, facilitating a comparable capacity realization with pristine state. Thereby, even though it has long been accepted that there is a trade-off in relation to cation doping with entailed capacity limitation^22,23,25, this assertion contains a principal exception in case of H-MoO₃ since the lithium intercalation sites are rearranged not by the cation interposition but by proton interference on Mo-O_a bonding.

We also investigated a role of H-binding in determining the diffusion rates by constructing the Li-ion diffusion paths and calculating the energy barriers using NEB simulation. According to the ARXPS results (Fig. S16), showing that the proton doping would occur throughout the surface and bulk regions of metal oxide, the energy barriers for available diffusion pathways of both pristine MoO₃ and H-MoO₃ (Figs. S17 and S18) were calculated on the basis of the most stable inter-layer site. The energy barrier for single Li-ion diffusion pathway along the inter-layer sites in pristine MoO₃ is 0.5 eV, whereas, in case of H-MoO₃ having various diffusion routes due to the asymmetrical lattice orders, the rate determining energy barrier for Li-ion moving along the inter-layer sites is only 0.397 eV as shown in Fig. 4c. Moreover, the energy barrier of Li-ion moving from intra-layer to inter-layer is 0.338 eV as shown in Fig. S18. That is, through the advent of inter-layer* position with various diffusion pathways as a result of asymmetrical lattice order by proton introduction, the bottleneck energy barrier for Li-ion diffusion through the bulk regions could be lowered by approximately 0.1 eV as shown in Fig. 4d. Therefore, we concluded that lattice distortion by proton adoption would modulate the electrical and redox characteristics, resulting in reversible cycling performance and faster kinetics of Li-ion along the intercalation sites of H-MoO₃.

In this work, we established the cornerstone of metal oxide hydrogenation by devising a novel cation-solution treatment strategy and demonstrated that the impetus of a proton diffusion through the oxide lattice is based on the galvanic redox reactions. Herein, we could verify though the experimental proof that the standard potentials of oxide and metallic cations are vital factors for the controllable proton doping. This methodology not only encompasses the implicit principle of conventional solid-metal treatment for oxide hydrogenation but also unveils the phase transition mechanism of metal oxide during electron-proton pair migration. Based on the thorough understanding of hydrogenation mechanisms, sole impact of H-binding with practical applicability of this method for intercalation-type energy storage materials in lithium-ion battery systems are demonstrated. In battery systems, there are significant differences in redox characteristics as protons participate in orthorhombic-MoO₃. Typically, the proton doping with lattice rearrangement would cause the suppressed irreversible phase transition reaction and accelerated Li-ion diffusion with enhanced charge transfer reaction. Through the first principle DFT calculation, it is confirmed that the interposition of protons was entirely distinguished compared with other cation dopants, which results suggest the new possibilities to overcome the trade-off in relation between cation doping and limited capacity for energy storage. Moreover, it could be demonstrated via NEB approach that asymmetric lattice order results in diffusion pathways of Li-ion having lower energy barriers along the intercalation sites, contributing to enhanced diffusion rates and pseudo-capacitive characteristics. We believed that this work would suggest new insight of oxide reforming strategy via corrosion-based galvanic reaction and highlight the sole impact of H-binding on inherent properties of oxide for preferable materials engineering.

Material preparation.

Orthorhombic structure MoO₃ (α-MoO₃) was synthesized through a one-step hydrothermal synthesis. Ammonium molybdate tetrahydrate (2 g, Sigma Aldrich) was added to 30 ml of deionized water and 10 ml of nitric acid (60%, Daejung) to form a solution. The prepared solution was transferred into a 100 ml Teflon-lined autoclave and heated in box furnace at 180 ^oC with the constant 5 ^oC min^− 1 of heating rate for 12 h. The obtained white powder was washed with distilled water several times using vacuum filtering, and dried under vacuum at 70 ^oC. As for monoclinic WO₃, it is purchased from Sigma-Aldrich (CAS no: 1314-35-8) and used without any purifications. For metal oxide hydrogenation, Molybdenum (Ⅳ) solution was prepared by dissolving the specific amount of molybdenum chloride (MoCl₅, Sigma Aldrich) in 10 ml of acetonitrile (CARLO ERBA) and 10 ml deionized water. Vanadium (Ⅱ) solution was prepared by dissolving the specific amount of ammonium metavanadate dissolved in 30 ml of deionized water and 10 ml of sulfuric acid (Daejung) and excess amount of zinc metal powder was added. The obtained solution was refined using vacuum filtering to remove the residual metal. Galvanic redox reaction induced metal oxide hydrogenation begin as the metallic cation solutions are added at the 0.2 g of metal oxide (MoO₃, WO₃) dispersed deionized water and stirred for 3 h at room temperature. The reduced metal oxide powder was washed with deionized water for several times to remove the residual metallic cation solutions and collected using vacuum filtering.

Material characterization.

The structural properties of samples were analyzed by X-ray diffraction (XRD; Rigaku) using Cu Kα radiation (λ = 0.15406 nm) and the interlayer plane distances were estimated by the using (020) reflection. Ex-situ XRD was performed in Rigaku (Smartlab) using Cu Kα radiation (λ = 0.15406 nm) by film mode The samples were prepared after electrode polarization by linear sweep voltammetry (LSV) with the 0.1 mV s^− 1 of scan rate in Li-ion battery coin-cell systems. The electrode potential shift to 1.5 and 3.5 V vs, Li/Li+, respectively, to evaluate the fully charged/discharged condition, and the polarized electrodes were obtained after cell disassembling, followed by rinsing with dimethyl carbonate (DMC) solvent and dried naturally in argon purged glove box. Oxidation configurations of prepared samples are conducted using X-ray photoelectron spectroscopy (XPS, Thermo Fisher Scientific) using Al Kα (1486.6 ev) for excitation source at 100 W, and angle-resolved XPS (ARXPS) analysis for H-MoO₃ was conducted by film mode with the photoelectron tilt angle from zero to 70^o. The surface morphologies of synthesized MoO₃ were collected using high resolution transmission electron microscopy (TEM, Tecnain Fe F30 S-Win) and high-resolution scanning electron microscopy (SEM, S-4700 with EMAX system, Hitachi), and the element mapping images of MoO₃ were measured by JSM-7500F (JEOL). Raman spectroscopy (Horiba) was measured with BX41 confocal microscope and the Fourier transform infrared spectrometer (FT-IR, Bruker) was measured by transmission mode.

Electrochemical analysis.

The redox features of pristine MoO₃ under acidic condition were measured in a three-electrode systems using a rotating disk electrode (RDE, 0.196 cm², glassy carbon) as working electrode, saturated calomel electrode (SCE) as reference electrode, and Pt mesh as counter electrode. The polarization curve of pristine MoO₃ was measured by linear sweep voltammetry (LSV) with the 10 mV s^− 1 of scan rate from open circuit voltage (OCV, around 0.4 V_SCE) to -0.8 V_SCE under N₂ saturated 1M H₂SO₄ solution. The standard redox potential of molybdenum cation under 1M H₂SO₄ was measured in a three-electrode system using Pt mesh, SCE, and Pt rod as working, reference, and counter electrode, respectively. The polarization curves were measured by cyclic voltammetry (CV) between − 0.3 to 0.8 V_SCE with the 10 mV s^− 1 of scan rate. For the conversion of the applied potential vs. SCE, the potentials of the obtained results are converted to the reversible hydrogen electrode (RHE) according to Nernst Equation: E_RHE = E_SCE + E^o_SCE + 0.059 pH. The redox characterizations of prepared samples in Li-ion battery systems were investigated in two-electrode system using CR2032-type coin cell. The slurry, composed of the active materials (pristine MoO₃, H-MoO₃), supporting carbon (Super P), and binder (PAA) with a weight ratio of 7:2:1, was cast on Al foil, and the electrode was dried at 60 ^oC for 24 h in a vacuum oven. The coin cell was assembled with prepared electrode with a diameter of 10 mm (around 0.4 ~ 0.6 mg of loading mass: 0.50 ~ 0.76 mg cm^− 2) as working electrode, Li metal (16 pi) as counter/reference electrode, a piece of propylene film (Celgard 2400) as separator, and 1 M of lithium hexafluorophosphate (LiPF₆) dissolved in a mixture of ethylene carbonate and diethylene carbonate (EC/DEC, 1:1 by volume) as electrolyte in an argon gas-filled glove box. The electrochemical properties of assembled coin cell were investigated between 1.5 and 3.5 V vs. Li/Li⁺ of potential regions using potentiostat (Solatron Analytical, 1470E/1400 CellTest System) and battery cycler (WonATech, WBCS3000). The cyclic performances were measured at various specific current density of 0.1, 0.2, 0.3, 0.4, 0.5, 1.0, 2.0, and 3.0 A g^− 1 to evaluate the rate capability. Long-term cycling tests were performed at specific current density of 1,000 mA g^− 1 for durability test in the potential range of 1.5–3.5 V vs. Li/Li⁺.

Computational details

To investigate the energetics of Li ion migration within pristine MoO₃ and H_nMoO₃ with n = 0.5, we carried out first-principles electronic structure calculations within density functional theory (DFT) scheme as is implemented with Vienna Ab initio Simulation Package (VASP) 5.4 ^30–34. A plane-wave basis set with 500eV energy cut-off is employed for the solution of the Kohn-Sham equation, and the exchange-correlation interactions among electrons are described within generalized gradient approximations (GGA) ³⁵. Moreover, the DFT-D3 functional of Grimme et al. ³⁶ is chosen to properly treat the van der Waals interactions in MoO₃ and H_0.5MoO₃ (Table S1). To optimize all geometric structures, the unit cells of pristine MoO₃ and H_0.5MoO₃ which is two times larger in the y-direction, due to the setting for n = 0.5, are fully relaxed until the energy and force differences between successive relaxation steps becomes less than 10^-5eV and 10^-2eV/Å, respectively. In calculations, $3\times 2\times 1$ and $3\times 1\times 1$ supercells are employed for MoO₃ and H_0.5MoO₃, respectively, together with Γ-centered $3\times 5\times 3$ k-point grids for the Brillouin zone sampling.

To study Li diffusion, the energy barrier simulations are performed based on the climbing image nudged elastic band (CI-NEB) method with a force-based optimization scheme^37,38. The forces convergence threshold orthogonal to the band is set to be less than 0.01 eV/Å in our CI-NEB calculations. For evaluating the structural stability of the initial and final states, formation energies (${{\Delta }\text{H}}_{f}$) are calculated (Table S2) by the following equations:

$${{\Delta }\text{H}}_{f}=E\left[\text{L}\text{i}+\left({\text{H}}_{0.5}\right)\text{M}\text{o}{\text{O}}_{3}\right]-E\left[\left({\text{H}}_{0.5}\right)\text{M}\text{o}{\text{O}}_{3}\right]-E\left[\text{L}\text{i}\right]$$

where the $E\left[\text{L}\text{i}+\left({\text{H}}_{0.5}\right)\text{M}\text{o}{\text{O}}_{3}\right]$ and $E\left[\left({\text{H}}_{0.5}\right)\text{M}\text{o}{\text{O}}_{3}\right]$ are the total energy of (H_0.5)MoO₃ system with and without one Li atom, respectively, and $E\left[\text{L}\text{i}\right]$ is the chemical potential which is the per atom energy from bcc Li metal.

Lu N et al (2022) Enhanced low-temperature proton conductivity in hydrogen-intercalated brownmillerite oxide. Nat Energy 7:1208–1216. https://doi.org:10.1038/s41560-022-01166-8
Guo Y et al (2019) Hydrogen-Location-Sensitive Modulation of the Redox Reactivity for Oxygen-Deficient TiO(2). J Am Chem Soc 141:8407–8411. https://doi.org:10.1021/jacs.9b01836
Zhou Y et al (2016) Strongly correlated perovskite fuel cells. Nature 534:231–234. https://doi.org:10.1038/nature17653
Cheng S et al (2021) Tuning electromagnetic absorption properties of transition metal oxides by hydrogenation with nascent hydrogen. Chem Eng J 417. https://doi.org:10.1016/j.cej.2020.127980
Zhu Q et al (2020) Hydrogen-Doping-Induced Metal-Like Ultrahigh Free-Carrier Concentration in Metal-Oxide Material for Giant and Tunable Plasmon Resonance. Adv Mater 32:e2004059. https://doi.org:10.1002/adma.202004059
Xu T et al (2023) Discovery of fast and stable proton storage in bulk hexagonal molybdenum oxide. Nat Commun 14:8360. https://doi.org:10.1038/s41467-023-43603-6
Li M et al (2023) Hydrogen spillover as a promising strategy for boosting heterogeneous catalysis and hydrogen storage. Chem Eng J 471. https://doi.org:10.1016/j.cej.2023.144691
Salehabadi A, Dawi EA, Sabur DA, Al-Azzawi WK, Salavati-Niasari M (2023) Progress on nano-scaled alloys and mixed metal oxides in solid-state hydrogen storage; an overview. J Energy Storage 61. https://doi.org:10.1016/j.est.2023.106722
Xing F et al (2021) Tunable charge transfer efficiency in HxMoO3@ZnIn2S4 hierarchical direct Z-scheme heterojunction toward efficient visible-light-driven hydrogen evolution. Appl Catal B 285. https://doi.org:10.1016/j.apcatb.2020.119818
Xie C et al (2020) In-situ phase transition of WO3 boosting electron and hydrogen transfer for enhancing hydrogen evolution on Pt. Nano Energy 71. https://doi.org:10.1016/j.nanoen.2020.104653
Chen X et al (2021) Hydrogenated Oxide as Novel Quasi-metallic Cocatalyst for Efficient Visible-Light Driven Photocatalytic Water Splitting. J Phys Chem C 125:12672–12681. https://doi.org:10.1021/acs.jpcc.1c02991
Zhang S et al (2021) Boosting selective hydrogenation through hydrogen spillover on supported-metal catalysts at room temperature. Appl Catal B 297. https://doi.org:10.1016/j.apcatb.2021.120418
Xiong M, Gao Z, Qin Y (2021) Spillover in Heterogeneous Catalysis: New Insights and Opportunities. ACS Catal 11:3159–3172. https://doi.org:10.1021/acscatal.0c05567
Yin H, Kuwahara Y, Mori K, Louis C, Yamashita H (2020) Properties, fabrication and applications of plasmonic semiconductor nanocrystals. Catal Sci Technol 10:4141–4163
Chen Y et al (2018) Non-catalytic hydrogenation of VO(2) in acid solution. Nat Commun 9:818. https://doi.org:10.1038/s41467-018-03292-y
Xie L et al (2020) Tunable Hydrogen Doping of Metal Oxide Semiconductors with Acid-Metal Treatment at Ambient Conditions. J Am Chem Soc 142:4136–4140. https://doi.org:10.1021/jacs.0c00561
Lei Y et al (2023) Discovery of a three-proton insertion mechanism in alpha-molybdenum trioxide leading to enhanced charge storage capacity. Nat Commun 14:5490. https://doi.org:10.1038/s41467-023-41277-8
Guo H et al (2020) Two-Phase Electrochemical Proton Transport and Storage in α-MoO3 for Proton Batteries. Cell Rep Phys Sci 1. https://doi.org:10.1016/j.xcrp.2020.100225
Wang D (2007) Biogeochemistry of redox-sensitive elements in natural waters: chemical speciation of molybdenum and vanadium. State University of New York at Stony Brook
Li X, Zhang H, Mai Z, Zhang H, Vankelecom I (2011) Ion exchange membranes for vanadium redox flow battery (VRB) applications. Energy Environ Sci 4. https://doi.org:10.1039/c0ee00770f
Tang Y et al (2021) Lattice Proton Intercalation to Regulate WO3-Based Solid‐Contact Wearable pH Sensor for Sweat Analysis. Adv Funct Mater 32. https://doi.org:10.1002/adfm.202107653
Mai LQ et al (2007) Lithiated MoO3 Nanobelts with Greatly Improved Performance for Lithium Batteries. Adv Mater 19:3712–3716. https://doi.org:10.1002/adma.200700883
Dong Y et al (2015) Inhibiting effect of Na + pre-intercalation in MoO3 nanobelts with enhanced electrochemical performance. Nano Energy 15:145–152. https://doi.org:10.1016/j.nanoen.2015.04.015
Yu M et al (2020) Interlayer gap widened alpha-phase molybdenum trioxide as high-rate anodes for dual-ion-intercalation energy storage devices. Nat Commun 11:1348. https://doi.org:10.1038/s41467-020-15216-w
Kim HS et al (2017) Oxygen vacancies enhance pseudocapacitive charge storage properties of MoO(3-x). Nat Mater 16:454–460. https://doi.org:10.1038/nmat4810
Choi C et al (2019) Achieving high energy density and high power density with pseudocapacitive materials. Nat Reviews Mater 5:5–19. https://doi.org:10.1038/s41578-019-0142-z
Yang X, Rogach AL (2019) Electrochemical Techniques in Battery Research: A Tutorial for Nonelectrochemists. Adv Energy Mater 9. https://doi.org:10.1002/aenm.201900747
Huang PR, He Y, Cao C, Lu ZH (2014) Impact of lattice distortion and electron doping on alpha-MoO3 electronic structure. Sci Rep 4:7131. https://doi.org:10.1038/srep07131
Cheng H et al (2016) Hydrogen Doped Metal Oxide Semiconductors with Exceptional and Tunable Localized Surface Plasmon Resonances. J Am Chem Soc 138:9316–9324. https://doi.org:10.1021/jacs.6b05396
Kresse G, Hafner J (1994) Ab initio molecular-dynamics simulation of the liquid-metal-amorphous-semiconductor transition in germanium. Phys Rev B Condens Matter 49:14251–14269. https://doi.org:10.1103/physrevb.49.14251
Kresse G, Hafner J (1993) Ab initio molecular dynamics for liquid metals. Phys Rev B Condens Matter 47:558–561. https://doi.org:10.1103/physrevb.47.558
Kresse G, Furthmüller J (1996) Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set. Comput Mater Sci 6:15–50
Kresse G, Joubert D (1999) From ultrasoft pseudopotentials to the projector augmented-wave method. Phys Rev B 59:1758
Blochl PE (1994) Projector augmented-wave method. Phys Rev B Condens Matter 50:17953–17979. https://doi.org:10.1103/physrevb.50.17953
Perdew JP, Burke K, Ernzerhof M (1996) Generalized gradient approximation made simple. Phys Rev Lett 77:3865
Grimme S, Antony J, Ehrlich S, Krieg H (2010) A consistent and accurate ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu. J Chem Phys 132:154104. https://doi.org:10.1063/1.3382344
Sheppard D, Terrell R, Henkelman G (2008) Optimization methods for finding minimum energy paths. J Chem Phys 128:134106. https://doi.org:10.1063/1.2841941
Sheppard D, Xiao P, Chemelewski W, Johnson DD, Henkelman G (2012) A generalized solid-state nudged elastic band method. J Chem Phys 136:074103. https://doi.org:10.1063/1.3684549

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Galvanic Hydrogenation Reaction in Metal Oxide

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