Trimetallic Ni-CuCoN0.6 Ohmic junction for the enhanced oxidation of methanol and urea.

ABSTRACT

Methanol oxidation reaction (MOR) and urea oxidation reaction (UOR) can be utilized as effective alternatives to the anodic oxygen evolution reaction (OER) in overall water-splitting. Nevertheless, the development of cost-effective, highly efficient and durable electrocatalysts for MOR and UOR remains a significant challenge. Herein, the Ohmic junction (Ni-CuCoN0.6@CC) comprising CuCoN0.6 nanosheets and Ni nanoparticles anchored on carbon cloth (CC) was successfully synthesized via a two-step hydrothermal process followed by pyrolysis. The Ni-CuCoN0.6@CC demonstrates exceptional performance in both MOR (1.334 V@10 mA cm-2) and UOR (1.335 V@10 mA cm-2), coupled with outstanding durability, maintaining 88.70 % current density for MOR and 88.92 % for UOR after a rigorous 50-h stability test. Furthermore, the Ni-CuCoN0.6@CC demonstrates a high selectivity for oxidizing methanol to formic acid, achieving Faraday efficiencies exceeding 90 % at various current densities in the context of MOR. The outstanding performance of Ni-CuCoN0.6@CC in terms of MOR and UOR either surpasses or closely approaches the levels reported in previous literature, primarily due to the synergistic effect resulting from the Ohmic junction in this system, Ni serves as the principal active component, Co augments catalytic activity and diminishes onset potential, while Cu enhances long-term durability. Moreover, CuCoN0.6 nanosheets effectively modulate electronic structure and optimize the morphology of Ni, leading to the exposure of numerous defects that provide a wealth of active sites for the reaction. Additionally, the exceptional hydrophilic and aerophobic surface promotes enhanced mass transfer. Density functional theory (DFT) calculations show that Ni-CuCoN0.6@CC enhances reactant adsorption and product desorption, reducing energy barriers and expediting MOR and UOR kinetics.