The electrocatalytic nitrate reduction reaction (NO₃RR) to ammonia is deemed as an ideal strategy to balance the global nitrogen cycle. However, the cycling of active sites by proton transfer is highly likely to result in poor faradaic efficiency (FE) of catalysts at potentials relevant to the hydrogen evolution reaction, especially in neutral solutions. Herein, we report the construction of an unprecedented mirror-symmetric nanoarray (MSN) assembled by c-axis-oriented single-crystalline WO₃ nanoneedles, and design oxygen-deficient MSN-WO_3−x to anchor ultrasmall Ru nanoclusters for the neutral NO₃RR. Impressively, the resultant Ru/MSN-WO_3−x exhibits an outstanding ammonia FE of 95.1% at 0 V vs. RHE and delivers an excellent ammonia production rate of 12.38 mg h⁻¹ cm⁻² at a low potential of −0.6 V in a neutral electrolyte, which is 6.32 times that of commercial Ru/C (1.96 mg h⁻¹ cm⁻²). Additionally, the Ru mass activity of Ru/MSN-WO_3−x is 4.6–9.5 times that of commercial Ru/C at various potentials. In situ surface enhanced Raman spectroscopy (SERS) combined with multiple characterization reveal that the electrochemically induced hydrogen intercalation occurs before the NO₃RR on Ru/MSN-WO_3−x, which can trigger the phase transformation to generate the real active species (Ru/MSN-H_yWO_3−x) with an accelerated hydrogenation process to ammonia. Further theoretical calculations indicate that bulk hydrogen intercalation is accompanied by altered electronic structures with band repositioning in H_yWO_3−x, which also accounts for the boosted hydrogenation process during the NO₃RR.

中文翻译：

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镜对称 Ru/WO3−x 纳米阵列中的原位体氢嵌入促进了中性电催化硝酸盐还原为氨


电催化硝酸盐还原反应 （NO₃RR） 对氨被认为是平衡全球氮循环的理想策略。然而，质子转移对活性位点的循环极有可能导致催化剂在与析氢反应相关的电位下法拉第效率 （FE） 不佳，尤其是在中性溶液中。在此，我们报道了由 c 轴取向单晶 WO₃ 纳米针组装的前所未有的镜像对称纳米阵列 （MSN） 的构建，并设计了缺氧 MSN-WO _3-x 来锚定中性 NO₃RR 的超小 Ru 纳米簇。令人印象深刻的是，所得的 Ru/MSN-WO _3-x 在 0 V 下与 RHE 相比表现出 95.1% 的出色氨 FE，并且在中性电解质中提供 12.38 mg ^{h-1 cm-2} 的出色氨生成速率和 -0.6 V 的低电位，是商用 Ru/C （1.96 mg ^{h-1 cm-2}） 的 6.32 倍。此外，在各种电位下，Ru/MSN-WO _3-x 的 Ru 质量活性是商业 Ru/C 的 4.6-9.5 倍。 原位表面增强拉曼光谱 （SERS） 结合多重表征表明，电化学诱导的氢嵌入发生在 Ru/MSN-WO _3-x 上的 NO₃RR 之前，这可以触发相变以产生真正的活性物质 （Ru/MSN-H_yWO_3-x） 加速加氢制氨。进一步的理论计算表明，本体氢插层伴随着电子结构的改变，并在 H_yWO _3-x 中具有带重新定位，这也解释了 NO₃RR 期间增强的氢化过程。