Methanol-Assisted Hybrid Electrolysis for Green Hydrogen and Formate Production Using a Trifunctional Cu–Co–Mo Oxide Catalyst

Tackling the global energy crisis and environmental pollution driven by rising fossil fuel consumption requires the development of renewable, green, and continuous energy sources. Hydrogen (H2) production via renewable energy-powered water electrolysis offers a sustainable solution, where development of efficient, cost-effective electrocatalysts is critical. This article reports nickel foam (NF)-supported relatively unexplored trimetallic Cu–Co–Mo oxide (CuCoMo-O/NF) costing $0.051 cm–2, as a trifunctional electrocatalyst for the methanol oxidation reaction (MOR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). The CuCoMo-O/NF catalyst demonstrates superior electrocatalytic activity compared to its monometallic and bimetallic counterparts (Co3O4/NF, CoMo-O/NF, and CuCo-O/NF). CuCoMo-O/NF exhibits 244 mV (OER) and 234 mV (HER) overpotential at 50 mA cm–2, where MOR required a 74 mV lower potential than the OER. The fabricated conventional CuCoMo-O/NF(±) electrolyzer operates at 1.803 V to deliver 100 mA cm–2, significantly reduced to 1.623 V in the MOR-integrated hybrid electrolyzer, which simultaneously valorizes methanol to formate ions in a greener way while boosting H2 production. Both electrolyzers display remarkable long-term stability over 100 h. The Faradaic efficiency (FE) of the electrolyzers is ∼99.4%, with an electricity cost for H2 production of $1.25 kg–1 for the conventional electrolyzer, which has been further reduced to $0.95 kg–1 using the hybrid CuCoMo-O/NF(±) electrolyzer, meeting the U.S. Department of Energy target (<$2 kg–1). These findings demonstrate the practical applicability of CuCoMo-O/NF for scalable and sustainable H2 production.