Atomic Layered NiO/Phosphorus-Doped MnO2 P-N Junctions: A Pathway to High-Performance Supercapattery Devices

This article introduces an innovative approach to enhancing electrochemical energy storage by leveraging the inherent electric field of a p–n junction electrode, which improves charge transport at the interface. In this study, a p–n junction was formed between n-type phosphorus-doped MnO2 nanosheets and a p-type NiO atomic layer, prepared using hydrothermal, phosphorylation, and atomic layer deposition processes. The addition of phosphorus ions enhanced electrical conductivity by introducing numerous active sites, which are crucial for energy storage. High-efficiency charge transfer was ensured by the built-in electric field at the heterointerface of the p-type NiO and n-type phosphorus-doped MnO2. The ultrathin NiO atomic layer on the phosphorus-doped MnO2 stabilized the surface, facilitating prolonged electrochemical reactions and delivering a higher specific capacitance than pristine phosphorus-doped and undoped MnO2 electrodes. Furthermore, an all-solid-state supercapattery device was developed, consisting of 5 nm NiO ALD on P-doped MnO2 // rGO, which delivered a specific capacitance of 208 F/g and exhibited a high energy density of 71.98 Wh/kg at a power density of 750 W/kg. This remarkable electrochemical performance and stability confirms that the constructed p–n junction electrode could produce desirable materials for next-generation supercapacitors.