Strengthening the Hydrogen Spillover Effect via the Phase Transformation of W₁₈O₄₉ for Boosted Hydrogen Oxidation Reaction

The hydrogen spillover effect on metal-supported electrocatalysts is of great significance in hydrogen-involved reactions, especially in a hydrogen oxidation reaction (HOR). Herein, a facile thermal reduction method has been adopted to synthesize W₁₈O₄₉ (WO_2.72) nanospheres decorated with single nickel atoms, and the obtained Ni-WO_2.72-T (1.20 wt % Ni) was used as a probe catalyst for investigating the hydrogen spillover effect, which exhibits enhanced HOR performance, stability, and resistance to CO poisoning in acidic electrolytes. Based on in situ Raman spectroscopy and the density functional theory (DFT) calculation, a synergistic effect between Ni single-atom active sites and the hydrogen spillover effect is proposed to contribute to the HOR performance on Ni-WO_2.72-T. Briefly, the introduction of single Ni atoms induces electron redistribution on Ni-WO_2.72-T, making Ni atoms positively charged for H₂ adsorption and activation, and on the other hand, the reversible phase transformation between WO_2.72 and H_xWO_2.72 facilitates H* transfer from Ni to WO_2.72, i.e., hydrogen spillover, resulting in elevating the HOR catalytic activity. Both experimentation and theoretical calculations demonstrate that the reversible phase transformation of the WO_2.72 substrate strengthens the hydrogen spillover effect and thus elevates the HOR catalytic performance, which is believed to be helpful in designing highly active catalysts for hydrogen-involving reactions.