Oxygen vacancy rich δ-MnO2 nanosheets encapsulating single cobalt atoms-anchored carbon nanotubes for efficient oxygen evolution

Oxygen vacancy (OVac) and interface engineering are effective tactics for regulating the electronic structure of electrocatalysts and optimizing the absorption/desorption of reactants and intermediates on the catalyst surface to enhance the oxygen evolution reaction (OER). Herein, a self-supported electrocatalyst, comprising δ-MnO2 nanosheets grown on Co single atoms (CoSAs) anchored on N-doped carbon nanotubes (NCNTs) embedded with Co nanoparticle on a carbon cloth (CC) (δ-MnO2/CoNP@CoSAs-NCNTs/CC), was fabricated. Through insitu growth of δ-MnO2 nanosheets on CoNP@CoSAs-NCNTs/CC, the number of OVac is increased, as proved by X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and Positron annihilation lifetime spectrometer (PALS), due to the redox between MnO2 and Co. Experimental results and theoretical calculations confirm that the formation of OVac rich δ-MnO2 nanosheets and the construction of heterogeneous interface between δ-MnO2 and CoSAs-NCNTs endow the electrocatalyst with good conductivity, fast charge transfer, and multiple active sites, leading to rapid OER kinetics. Therefore, the δ-MnO2/CoNP@CoSAs-NCNTs/CC electrocatalyst demonstrates remarkable OER performance, requiring only 165 mV overpotential to reach a current density of 10 mA/cm2 in an alkaline solution.