Highly Conductive Non-Calcined 2D Cu0.3Co0.7 Bimetallic–Organic Framework for Urea Electrolysis in Simulated Seawater

Abstract

Global clean energy demands can be effectively addressed using the promising approach of hydrogen energy generation combined with less energy consumption. Hydrogen can be generated, and urea-rich wastewater pollution can be mitigated in a low-energy manner using the urea oxidation reaction (UOR). This paper seeks to assemble a unique electrocatalyst of a pristine 2D MOF, [Co(HBTC)(DMF)]_n (Co-MUM-3), from 1,3,5-benzenetricarboxylate (BTC) to oxidize urea in simulated seawater. Ni foam (NF)-based working electrodes were fabricated by incorporating a series of heterometallic CuCo-MUM-3 frameworks (Cu_0.1Co_0.9-MUM-3, Cu_0.2Co_0.8-MUM-3, Cu_0.3Co_0.7-MUM-3, and Cu_0.4Co_0.6-MUM-3), after which their application in the urea oxidation reaction was examined. A very low required overpotential [1.26 V vs reversible hydrogen electrode (RHE) in 1 M KOH + 0.5 M NaCl (simulated seawater) + 0.33 M urea] and a Tafel slope of 112 mV dec^–1 could be observed for the Cu_0.3Co_0.7-MUM-3 electrocatalyst, ensuring the achievement of urea electro-oxidation and hydrogen evolution reactions at a corresponding 10 mA cm^–2 electrocatalytic current density. A relatively lower overpotential will be evident compared to other reported pristine MOFs, outperforming the commercial catalyst RuO₂ (1.41 V at 10 mA cm^–2, 131 mV dec^–1) and ensuring considerable stability at significantly high current densities for a minimum of 72 h.