Coupled intramolecular/heterointerfacial electron transfer in polyelectrolyte-shielded Iso-type black phosphorus hetero-structure boosts oxygen reduction kinetics

Abstract

Searching new structured black phosphorus (BP) and exploring intriguing functions and applications have become a hot topic so far. Here, we introduce a novel Iso-type black phosphorus heterostructure guided by first principle calculation, which features unique heterointerface and electronic coupling interaction via stacking assembly of exfoliated black phosphorus (EBP) and amine-functionalized EBP (N-EBP). Inspired by the theoretical results, we constructed the Iso-type heterostructure comprising of ultrathin exfoliated few-layered EBP and N-EBP, both of which were derived from identical bulk BP. The purposive amine-functionalization not only creates positively-charged P atoms on N-EBP as effective active sites via N-induced intramolecular electron transfer (IET) but also endows N-EBP with lower work function relative to EBP, while the unique EBP/N-EBP Iso-type heterostructure engenders directional heterointerfacial electron transfer (HET). The coupled IET/HET effects optimize the charge redistribution to afford favorable O2 adsorption. In this case, our unique strategy for the first time exploits the inherent catalytic capability of BP toward the oxygen reduction reaction (ORR) and enables the first use of BP as metal-free ORR catalysts for Zn-air cells. The newly-designed heterostructure facilitates a 4-e− transfer ORR relative to inactive EBP or N-EBP. Importantly, the polymer-shielded heterostructure acts as efficient air electrodes to endow a primary Zn-air cell with high stability, large capacity and high energy density—superior to the commercial Pt/C-enabled cell. This study as the first report on metal-free BP-based ORR catalysts and air electrodes not only extends BP’s application scopes but also renders new insight toward design of electronically-coupled superstructures for energy-related applications.