Efficient Tandem Electrocatalytic Nitrate Reduction to Ammonia on Bimodal Nanoporous Ag/Ag-Co across Broad Nitrate Concentrations.

Electrocatalytic nitrate (NO) reduction reaction (NORR) represents a promising strategy for both wastewater treatment and ammonia (NH) synthesis. However, it is difficult to achieve efficient NORR on a single-component catalyst due to NORR involving multiple reaction steps that rely on distinct catalyst properties. Here we report a facile alloying/dealloying-driven phase-separation strategy to construct a bimodal nanoporous Ag/Ag-Co tandem catalyst that exhibits a remarkable NORR performance in a broad NO concentration range from 5 to 500 mM. In 10 and 50 mM NO electrolytes, the NH yield rates reach 3.4 and 25.1 mg h mg with corresponding NH Faradaic efficiencies of 94.0% and 97.1%, respectively, outperforming most of the reported catalysts under the same NO concentration. The experimental results and density functional theory calculations demonstrate that Ag ligaments preferentially reduce NO to NO, while bimetallic Ag-Co ligaments catalyze the reduction of NO to NH.