Stable bifunctional nanoflower-structured NiMnCu-LDH catalyst for selective and efficient methanol-to-formate electrocatalytic conversion and hydrogen evolution reaction

Abstract

Low formate Faradaic efficiency (FE) and poor methanol-to-formate electrooxidation reaction (MOR) stability under high potentials restrict commercialization of coupling MOR with hydrogen evolution reaction (HER), which generates hydrogen and high-value-added formate simultaneously with low energy consumption. Herein, we synthesized a nanoflower-structured NiMnCu-LDH as bifunctional catalyst for both MOR and HER. Adding Cu suppresses oxygen evolution reaction (OER) and elevates Ni³⁺ content by promoting electron transfer from Ni²⁺ to Mn³⁺. NiMnCu-LDH exhibits high MOR activity with potentials of 1.33/1.36 V_RHE at 10/100 mA cm⁻², high formate selectivity with over 95 % FE at potential exceeding 1.50 V_RHE, and superior durability for at least 120 h in alkaline media. Furthermore, NiMnCu-LDH exhibits excellent HER performance with an overpotential of 76.45 mV at 10 mA cm⁻² with the existence of methanol. Producing hydrogen and formate is successively achieved by applying NiMnCu-LDH as both anode and cathode simultaneously for methanol electrolysis in a non-diaphragm electrolyzer.