Plasma-activated vacancy-rich RuO2/Co3O4 heterostructures enable high-performance borohydride electro-oxidation for direct borohydride fuel cells

Direct borohydride fuel cells (DBFCs) are promising energy conversion systems due to their high theoretical energy density, but their practical performance is limited by rapid borohydride hydrolysis and sluggish borohydride oxidation reaction (BOR) kinetics. Here, we report a plasma-engineered vacancy-rich RuO 2 /Co 3 O 4 heterostructure catalyst designed to accelerate BOR through coupled interfacial and defect modulation. The synergistic interaction between the heterointerface and oxygen vacancies tunes the electronic structure and facilitates the adsorption and conversion of key intermediates, thereby accelerating BOR kinetics. As a result, the catalyst exhibits a low overpotential of 133 mV, a charge-transfer resistance of 0.545 Ω, and a Tafel slope of 130.8 mV dec −1 . In a DBFC device, it delivers a peak power density of 361 mW cm −2 and retains 91.5% of its initial performance after 300 h of operation. These results demonstrate an effective strategy for enhancing BOR performance through coupled interface and defect engineering.