CuCo composite oxide synergistic catalysis: Electronic structure engineering boosts bifunctional activity for methanol fuel cells

Direct methanol fuel cells (DMFCs), which utilize liquid methanol as fuel, exhibit a high energy density of 6.13 kWh/kg and low pollution emissions, are widely regarded as ideal "green" energy converters. However, electrocatalysts are poisoned by methanol dehydrogenation intermediates (CO) during methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR), which inhibits electron transfer and slows reaction kinetics. Therefore, developing a high-performance, CO-tolerant bifunctional catalyst is crucial for achieving efficient and stable operation of DMFCs. In this study, synergistic active sites were generated through interaction of bimetallic composite oxides, thereby enhancing electron transfer efficiency and optimizing both MOR and ORR processes. Experimental results demonstrate that Cu_1.5Co_1.5O₄ catalyst shows significant room for improvement, with its onset potential (E_onset = 0.857 V) and half-wave potential (E_1/2 = 0.746 V) reaching 83 % of Pt/C catalysts. Demonstrating an outstanding current density of 75.76 mA cm^-2 coupled with superior CO resistance. In DMFCs, it delivered a competitive power density of 20.45 mW cm^-2. DFT calculations confirmed that composite oxide effectively regulates the binding energies of *CO and *OH intermediates, while notably reducing the overpotential in ORR theory. The changes in adsorption strength were further validated by d- and p-band center theory. This provides new design principles for the application of CuCo compositew oxides in DMFCs technology and clean energy systems.