Oxygen vacancy tuning of porous urchin-like nickel cobaltite for improved bifunctional electrocatalysis

Abstract

Proper regulating morphology and rationally distributing of active sites in a catalyst is crucial for improving its electrocatalytic performance. In this study, we synthesized a series of porous urchin-like NiCo2O4 structures through hydrothermal reaction and adjusted their morphologies and oxygen vacancies concentration by annealing them under different conditions. The resulting structure has interconnected pores that facilitate the fast transport of active species, assembled from many nanoneedles containing nanoparticles. Our results show that the porous urchin-like NiCo2O4 structure obtained after annealing at 400 °C under an argon atmosphere has the largest surface coverage area for redox species and the richest oxygen vacancies. This configuration demonstrates excellent performance in both methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR) in alkaline solution. Our findings offer a facile pathway to optimizing active sites on urchin-like NiCo2O4 structures, which could serve as bifunctional electrocatalysts for direct methanol fuel cells (DMFCs).