Hydration engineering of WO3 for optimizing hydrogen spillover: A first-principles guided approach to boost alkaline HER

The hydrogen evolution effect has been widely demonstrated to enhance the kinetics of the hydrogen evolution reaction (HER) by decoupling the water splitting and hydrogen recombination steps. Although interlayer water has been shown to promote proton transport in transition metal oxides and enhance the hydrogen evolution effect, the intrinsic mechanism underlying HER catalysis based on this process remains unclear. In this study, we systematically investigated the role of structural water in regulating the HER catalyzed by WO3 through first-principles calculations. By constructing a series of layered WO3 models with controllable hydration levels (WO3, WO3⋅0.5H2O, and WO3⋅H2O), we found that water intercalation significantly reduces the hydrogen adsorption energy, from −2.513 eV in the anhydrous state to −0.609 eV in the fully hydrated state, thereby optimizing hydrogen bonding strength to achieve an efficient HER. Electronic structure analysis indicates that water molecule intercalation alters the coordination environment of lattice oxygen, leading to a reduction in the density of states near the Fermi level. Crucially, the combined results of density functional theory and ab initio molecular dynamics calculations indicate that the interlayer insertion of water simultaneously increases the water splitting energy barrier. These findings suggest that the design of WO3-based HER catalysts should fully leverage the advantages of interlayer water in promoting proton transport and optimizing hydrogen adsorption, while the selection of synergistic materials should avoid reliance on the reverse hydrogen overflow mechanism, providing a clear design direction for the development of efficient WO3-based HER catalysts.