Fabricating cattle dung-derived nitrogen-doped biochar supported oxygen-deficient ZnO and Cu2O-based novel step-scheme photocatalytic system for aqueous Doxycycline hydrochloride mitigation and Cr (VI) reduction

The photoactive O-ZnO/Cu2O/NCDB heterojunction was fabricated by co-precipitation route to illustrate the advantage of utilizing photoinduced e--h+ pair in degrading Doxycycline hydrochloride and reducing Cr(VI) ions. Herein, we have engineered the electronic structure by generating Ov in ZnO that acts as an interface e- transfer mediator to promote heterojunction formation with Cu2O, supported by NCDB. The content of graphitic N in CDB was positively correlated with the photoactivity owing to the enhanced conductivity and facilitated e- migration. From XRD, XPS, and FTIR results, it was identified that pyridinic/pyrrolic/graphitic N in NCDB and generated Ov in ZnO lattice as dual active sites significantly courage the photocatalytic adsorption and degradation/reduction. The optimized S-scheme based O-ZnO/Cu2O/NCDB heterojunction displayed overall 88.9% Cr(VI) reduction (0.0105 min−1) and 92.9% DCHCl oxidation (0.0128 min−1) within 90 min. Overall, stable O-ZnO/Cu2O/NCDB exhibited the good efficacy of 86% and 89% over four consecutive cycles for Cr(VI) and DCHCl, respectively. This research work provides a neoteric idea for fabricating N-doped CDB along with visible active photocatalysts and deepens the mechanistic understanding for forming biochar-supported visible active S-scheme heterojunction.