Synthesis of morphology-controlled NiCu-electrocatalysts for efficient ammonia electrooxidation: Ni-Cu mutual cooperation mechanism

Abstract

Herein, facile synthesis of morphology-controlled NiCu-based electrocatalysts is presented using dodecylamine as a precipitation agent (NiCu-D). Several shapes, including scattering particles, spheres, and cubes, were created by adjusting the ratio of dodecylamine to metal precursor content. Compared with other precipitation agents, the optimized NiCu-D electrocatalyst exhibited a large electrochemically active surface area and an enhanced current density toward AOR. Cyclic voltammetry experiment found that NiCu-D-1:2/CP had a current density of 44.9 mA/cm2 at 0.6 V vs. Hg/HgO. In addition, we propose a new reaction pathway to explain the improvement in AOR reactivity after the addition of copper to the nickel system. This mechanism may explain how the two metals work together to lower the energy barrier, enhance reaction kinetics, and promote N2 selectivity. Furthermore, the influences of Cu insertion into the Ni electrode and the electrode’s active surface area were reflected in a substantial shift to N2 selectivity up to 79 %, which was confirmed using an in-operando gas chromatography (GC) system. This study not only proposes a facile method of synthesizing well-defined hierarchical electrocatalysts with elevated AOR activity but also provides valuable insight into the mutual impacts of Ni and Cu in AOR, paving the way for the design of highly selective electrodes.