Controllable oxygen vacancies and morphology engineering: Ultra-high HER/OER activity under base–acid conditions and outstanding antibacterial properties

Introducing vacancy defects and unique morphology is an effective strategy to improve the catalytic performance of transition metal compounds. However, precisely controlling the amount of vacancy defects remains challenging. Here, we propose a facile and efficient hydrothermal accompanying an annealing method to synthesize a series of Mn-doped CoO nanomaterials with controllable oxygen vacancies and unique morphology. The oxygen vacancies amount can be precisely controlled by adjusting the Mn-doping content and is positively correlated with catalytic performance. It was found that the oxygen vacancies amount can reach up to 38.2% over the Mn-doped CoO nanomaterials, resulting in ultra-high hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalytic activity (HER: 25.6 and 37 mV at 10 mA cm⁻²; OER: 301 and 322 mV at 50 mA cm⁻²) under both basic and acidic conditions, while reaching 10 mA cm⁻² for an ultra-low cell voltage of only 1.52 V, which exceeds that of Pt/C/RuO₂ and all reported non-noble metal oxide catalysts. The DFT calculations reveal oxygen vacancies can optimize H* and HOO* intermediates adsorption free energy, thus improving the HER and OER performance. Interestingly, the Mn-doped CoO with rich oxygen vacancies exhibits excellent antibacterial properties in vitro of biomedicine. This work provides new ideas and methods for the rational design and precise control of vacancy defects in transition metal compounds and explores their potential application value in electrochemical water splitting and biomedical fields.