Rational Design of Metallic NiTe_<i>x</i> (<i>x</i> = 1 or 2) as Bifunctional Electrocatalysts for Efficient Urea Conversion

Abstract

Electrocatalytic urea conversion (CO(NH2)2 + H2O → N2 + 3H2 + CO2) is a facile and scalable technique for urea-rich wastewater treatment, meanwhile with hydrogen evolution reaction (HER). However, it remains great challenge to develop a bifunctional catalyst for both HER and urea oxidation reaction (UOR) simultaneously due to the torpid kinetics of 6 e– transfer during UOR. Here, graphene oxide (GO) induced phase-controlled synthesis of nickel tellurides derived from Ni foam (NF) as freestanding electrocatalysts is reported. Results show that NF-assisted NiTe composited with reduced graphene oxide (rGO) exhibits superior activity for both HER and UOR. With the combined merits of HER and UOR, an efficient electrolyzer with integrated NiTe/rGO/NF was constructed as anode and cathode, representing overall urea decomposition at a low overpotential and even being driven by a commercial cell of 1.5 V. The metallic character and phase dependence of NiTe2 and NiTe toward UOR were simulated by density functional theory (DFT). The collective effects of rGO incorporation in morphology and phase for exposing more active sites and effective electron transport were discussed. It is extended to the direction of human urine conversion as well. Our study provides new insights into robust bifunctional electrocatalysts for urea splitting, which indicates promise for sustainable hydrogen evaluation and wastewater remediation.