Abstract
The development of efficient, low-cost electrocatalysts for the oxygen evolution reaction (OER) is crucial for advancing sustainable hydrogen production through water splitting. This study presents a dual-engineering strategy to enhance the OER performance of Co(3)O(4) by synthesizing hollow microspheres assembled from nanosheets (HMNs) with abundant oxygen vacancies and highly active crystal facet exposure. Through a modified one-step hydrothermal process, Co(3)O(4) HMNs with exposed (111) and (100) crystal facets were successfully fabricated, demonstrating superior OER activity compared to Co(3)O(4) nanocubes (NCs) with only (100) facet exposure. The optimized Co(3)O(4)-5% HMNs exhibited a low overpotential of 330 mV at 10 mA cm(-2) and a Tafel slope of 69 mV dec(-1). The enhanced performance was attributed to the synergistic effects of crystal facet engineering and defect engineering, which optimized the Co-O bond energy, increased the number of active sites, and improved conductivity. The unique hollow structure further facilitated mass transport and prevented nanosheet stacking, exposing more edge sites for catalytic reactions. This work highlights the potential of geometric and electronic structure modulation in designing high-performance OER catalysts for sustainable energy applications.