Electrocatalytic ammonia production from nitrite via dual-site Co3O4/NiO catalysts derived from laser-induced cyanonickelate frameworks

Abstract

Herein, we report the pioneering synthesis of the cobalt–nickel coordination frameworks (Co(H2O)2·Ni(CN)4, CoNi-CF) via pulsed laser irradiation in liquids (PLIL). The distinctive morphology of CoNi-CF has attracted considerable attention as a potential template to produce Co3O4/NiO composites with varying Co and Ni ratios. After subjecting CoNi-CF to a high-temperature calcination process at 400 °C, the resulting Co3O4/NiO composites displayed dual-active canters for efficient electrochemical nitrite (NO2−) reduction to ammonia (NH3). Optimizing the Co:Ni ratio at 1:0.75 yielded Co3O4/NiO with exceptional performance, achieving a remarkable 99.4 % Faradaic efficiency in NH3 production while maintaining a 96.1 % mass balance at −1.2 V vs. Ag/AgCl. Furthermore, this composite displayed long-term stability, degrading 60.82 % of NO2− in 180 min, with high NH3 yield rate (2012.03 μM h−1 cm−2) at −1.6 V vs. Ag/AgCl. The superior performance in NO2− reduction to NH3 can be attributed to the unique structural features inherited from CoNi-CF, including well-defined and self-standing Co3O4 and NiO phases. Synergistic effects at the oxide interface enhance electrochemical performance and facilitate efficient charge transfer kinetics of Co3O4/NiO, underscoring the unique potential of these composite materials.