Boosting the charge transfer kinetics in MOCVD prepared nitrogen doped hierarchical ZnO-Si nanowires for bifunctional photoelectrochemical water oxidation and organic contaminant removal

Abstract

Zinc oxide nanowires (ZnO NWs) are emerging as a promising photocatalyst for photoelectrochemical (PEC) energy generation and environmental remediation owing to their fascinating properties. However, a relatively wide band gap and low resistance to photo-corrosion limit their PEC activity. In this context, we report a rational strategy to fabricate hierarchical ZnO NWs on Si NWs (ZnO-Si NWs) via metal organic chemical vapor deposition (MOCVD) with nitrogen (N)-doping to alleviate the intrinsic drawbacks. The N-doped ZnO-Si NWs (N:ZnO-Si NWs) showed excellent light harvesting and efficient charge separation which boosted the PEC activities as compared with ZnO NWs. The fabricated photoanodes were examined for PEC water splitting and remediation of textile industry dye. N:ZnO-Si NWs exhibited 357 μA cm−2 photocurrent density (at 1.0 V vs Ag/AgCl) which was 3-fold higher than bare ZnO-Si NWs. In addition, N:ZnO-Si NW photoanodes showed remarkable PEC efficiency of 95 % toward methylene blue (MB) dye removal under AM 1.5 G illumination with 4 times reusability. These findings provide an efficient approach to developing a novel fabrication strategy for the construction of bifunctional PEC devices with exceptional water splitting and dye degradation efficiencies.