Classically, catalytic promotion in bimetallic catalysts has been ascribed to atomic-scale cooperativity between metal constituents. For catalytic reactions that could involve charge transfer, electron and ion flow may engender bimetallic promotion without atomic-level connectivity. Here we examine this hypothesis in the context of nitrate hydrogenation, a reaction catalysed almost exclusively by bimetallic catalysts. On state-of-the-art PdCu/C, nitrate hydrogenation to nitrite proceeds via electrochemical coupling of hydrogen oxidation and nitrate reduction half-reactions; Pd catalyses the former, while Cu catalyses the latter. Using this mechanistic framework, we predict how different Pd:Cu ratios affect nitrate hydrogenation rates, and rationalize the catalytic activity observed in PtAg/C and Ru/C. Finally, by only promoting the electrochemical hydrogen oxidation reaction with Ni(OH)₂, we synthesize PdNi(OH)₂Cu/C catalysts with comparable nitrate hydrogenation activity to our best-performing PdCu/C using fivefold less Pd. This work provides an alternative strategy for designing alloy catalysts for thermochemical redox transformations.

传统上，双金属催化剂的催化促进作用被归因于金属成分之间的原子级协同作用。对于可能涉及电荷转移的催化反应，电子和离子流可能会在没有原子级连接的情况下产生双金属促进。在这里，我们在硝酸盐氢化的背景下检验了这一假设，硝酸盐氢化是一种几乎完全由双金属催化剂催化的反应。在最先进的 PdCu/C 上，硝酸盐加氢生成亚硝酸盐是通过氢气氧化和硝酸盐还原半反应的电化学耦合进行的；Pd 催化前者，而 Cu 催化后者。利用这个机制框架，我们预测了不同的 Pd:Cu 比例如何影响硝酸盐氢化速率，并合理化在 PtAg/C 和 Ru/C 中观察到的催化活性。_{最后，仅通过 Ni(OH) 2}促进电化学氢氧化反应，我们合成了 PdNi(OH) ₂ Cu/C 催化剂，其硝酸盐加氢活性与我们性能最佳的 PdCu/C 相当，但 Pd 用量减少了五倍。这项工作为设计用于热化学氧化还原转变的合金催化剂提供了一种替代策略。