Interfacial effects in Ni(OH)2/MnO@Ni aerogel heterostructures promote highly efficient electrooxidation of ethylene glycol to formate and hydrogen

Abstract

The sluggish oxygen evolution reaction (OER: 4OH− → O2 + 2H2O + 4e−, E = 1.23 V vs RHE) retards the large-scale hydrogen production. Replacing OER with low-potential ethylene glycol oxidation reaction (EGOR) to drive water splitting is a promising approach to solve the high energy consumption in hydrogen production. Herein, we report an energy-efficient electrocatalytic water splitting system by using a heterostructure Ni(OH)2/MnO aerogel catalyst (NiMn AG) that replaces OER with ethylene glycol oxidation reaction (EGOR), resulting in the co-production of value-added formate and green hydrogen. Owing to the optimized electron distribution on the heterostructure interface, the NiMn AG catalyst exhibits excellent EGOR catalytic performance, with an overpotential of only 290 mV at 100 mA cm−2. The open-circuit potential of the reaction is reduced to 0.86 V for EGOR, rendering an earlier occurrence of electron transfer. The ion chromatography (IC) result demonstrates a highly selectivity (96%) for formate in EGOR. The density functional theory (DFT) calculations show that the interfacial effects between Ni(OH)2 and MnO optimizes the surface energy states of NiMn AG, improving the adsorption efficiency of the reaction intermediates for EGOR and further promoting the efficient cleavage of C–C to form formate. Additionally, the incorporation of MnO stabilizes the overall energy state during violent bond-breaking processes. This work sheds light on a new methodology to design bimetallic catalysts assisted by EGOR for decoupled green hydrogen production.