Exploiting the complete efficacy of 3D-nitrogen-doped ZnO nanowires photoanode via type-II ZnS core-shell formation toward highly stable photoelectrochemical water splitting

The hierarchical 3D-zinc oxide (ZnO) nanowires (NWs) photoanode promises high cost-to-efficiency ratios toward photoelectrochemical (PEC) water splitting owing to their enthralling characteristics. However, minimal visible light harvesting, and sluggish surface oxidation kinetics severely hinder the water-splitting efficiencies along with the resistance to photo-corrosion. We report a unique strategy of constructing type-II heterostructure of N-doped ZnO NWs with ultrathin zinc sulfide (ZnS) layer to form a core-shell structure that provides dual benefits of accelerating the charge transfer process and significantly enhancing the resistance to photo-corrosion of N-doped ZnO NWs. The PEC water splitting analyses showed that the optimal ZnS/N:ZnO core-shell NWs photoanode exhibited a photocurrent density of 0.85 mA cm−2 at 1.23 Vs RHE which was 3-fold higher than N:ZnO NWs photoanode. The ZnS shell encapsulation effectively protects the N:ZnO NWs core over a period of ∼16 h from detrimental photo-corrosion with 76% photocurrent density retention. Additionally, the integration of multilateral tactics of staggered heterojunction and core-shell formation provided higher photoconversion efficiencies over N:ZnO NWs. The reported approach may provide an alternative to address the sluggish surface kinetics that bothers the chemical stability, prolong the charge lifetime, and thus open up wide opportunities in the construction of efficient and highly stable PEC water-splitting devices.