Efficient Hydrogen Evolution Electrocatalyst: MoN/Ni3N/NF Coupled with Methanol Oxidation Reaction for Formate Production in Alkaline Media

Abstract

Electrocatalytic water splitting for hydrogen production is promising, but its practical application is limited by the sluggish kinetics of the anodic oxygen evolution reaction (OER) and the less valuable oxygen by-product. Hence, replacing OER with a thermodynamically favorable methanol oxidation reaction (MOR) and coupling with value-added formate generation on the anode is an energy-saving and effective scheme. In this work, we report a self-supporting bifunctional electrocatalyst MoN/Ni3N/NF, which exhibits excellent hydrogen evolution reaction catalytic activity and stability, requiring overpotentials of only 18 and 68 mV to reach current densities of −10 and −100 mA cm−2, respectively. Moreover, the catalyst’s performance minimally deteriorates after long-standing chronopotentiometry measurements (−100 mA cm−2@150 h). When MOR is used instead of OER, the required potential drops by 200 mV to 1.38 V at a current density of 100 mA cm−2 and MoN/Ni3N/NF also demonstrates splendid catalytic stability towards OER and MOR. Finally, a two-electrode system employing MoN/Ni3N/NF as a bifunctional electrocatalyst only requires a cell voltage of 1.40, 1.68 V to achieve current densities of 10 and 100 mA cm−2, respectively. The coupled electrolyzer also exhibits high faradaic efficiency for producing cathodic H2 (100%) and anodic formate (90%).