Currently, the construction of an acid-like catalyst surface in a high-pH electrolyte is advocated as one of the most pioneering strategies for significantly improving the catalytic activity of the alkaline hydrogen evolution reaction. However, the proton transfer kinetics that significantly determines the activity of the proton-coupled electron reaction is largely dependent on the usage of an extensive noble-metal bulk phase. Herein, a well-designed dynamic acid-like catalyst system constructed by the metallic WO₂ matrix and supported Ru single atoms (0.89 wt %) is grown on nickel foam (Ru SAC@WO₂/NF). The as-prepared Ru SAC@WO₂/NF free-standing catalyst exhibits superior activities of hydrogen evolution reaction with delivering current densities of 10, 50, and 200 mA/cm² only requiring overpotentials of ∼0, 40, and 84 mV, respectively, and an ultralow Tafel slope (38 mV/dec) in 1.0 M KOH electrolyte. Moreover, our deliberately prepared composite catalyst also shows long-term stability with negligible activity decay after continuous hydrogen generation at current densities of 10, 50, and 200 mA/cm² for more than 50 h. Comprehensive spectroscopy characterizations combined with density function theory calculations reveal that the significantly improved activity of alkaline hydrogen evolution reaction on the Ru SAC@WO₂/NF free-standing catalyst can be understood by two reasons: (i) the metallic WO₂ matrix contributes to the construction of an acid-like catalytic environment through the formation of weak-acid hydrogen tungsten bronze (H_xWO_y) intermediates on the solid–liquid interface in an alkaline electrolyte; (ii) unlike the weak electronic interaction between Ru nanoparticles and hydrogen atoms of weak-acid H_xWO_y intermediates, Ru single atoms are evidenced to efficiently tailor the acidity of H_xWO_y intermediates for accelerated deprotonation kinetics, thus resulting in the regeneration of active sites for next catalytic cycle. Such an interesting concept of catalyst design driven by basic chemical theories will benefit the exploration of noble-metal single atoms with ultralow usage but higher added-values in water electrolysis and beyond.

中文翻译：

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Ru 单原子调整金属二氧化钨的酸度以促进碱性析氢反应

目前，在高pH电解质中构建类酸催化剂表面被认为是显着提高碱性析氢反应催化活性的最具开创性的策略之一。然而，显着决定质子耦合电子反应活性的质子转移动力学在很大程度上取决于广泛的贵金属体相的使用。在此，在泡沫镍(Ru SAC@WO ₂ /NF)上生长了由金属WO ₂基体和负载Ru单原子(0.89wt%)构建的精心设计的动态类酸催化剂体系。所制备的Ru SAC@WO ₂ /NF自支撑催化剂表现出优异的析氢反应活性，只需~0、40和84 mV的过电势即可提供10、50和200 mA/cm ²的电流密度，分别在 1.0 M KOH 电解质中具有超低塔菲尔斜率 (38 mV/dec)。此外，我们精心制备的复合催化剂在10、50和200 mA/cm ²的电流密度下连续产氢50小时以上后，还表现出长期稳定性，活性衰减可忽略不计。综合光谱表征结合密度函数理论计算表明，Ru SAC@WO ₂ /NF自支撑催化剂上碱性析氢反应活性的显着提高可以通过两个原因来理解：（i）金属WO ₂基体有助于通过在碱性电解质中的固液界面上形成弱酸性氢钨青铜（H _x WO _y ）中间体来构建类酸催化环境； （ii）与Ru纳米粒子和弱酸H _x WO _{y中间体的氢原子之间的弱电子相互作用不同，Ru单原子被证明可以有效地调整H x} WO _y中间体的酸性以加速去质子化动力学，从而导致再生下一个催化循环的活性位点。这种由基础化学理论驱动的有趣的催化剂设计概念将有利于在水电解等领域探索超低用量但具有更高附加值的贵金属单原子。