Enhanced recycling and utilization of industrial waste gas H2S through photoelectrochemical methods with ZnFe2O4/ZnIn2S4 heterojunction containing NiCoP co-catalyst

Photoelectrochemical (PEC) H 2 S splitting offers a dual-functional strategy for sustainable hydrogen sulfide valorization and atmospheric remediation, but it is still hindered by sluggish charge dynamics and poor stability. Here, we pioneer a hierarchical ZnFe 2 O 4 /ZnIn 2 S 4 /NiCoP photoanode that synergistically integrates heterojunction engineering and surface cocatalyst modification to address these challenges. The enhanced photoinduced carrier separation is accomplished by ZnFe 2 O 4 /ZnIn 2 S 4 through accelerated charge transfer kinetics with role of built-in electric field and hybrid energy bands. Corresponding sulfur oxidization photocurrent density of 2.24 mA/cm 2 is achieved that is 8.30 folds higher than that of pristine ZnFe 2 O 4 . Subsequent modification with NiCoP nanoparticles further optimizes the surface electronic states, which include increased DOS and decreased R ct,trap , leading to accelerated charge injection dynamics and suppressed carrier recombination at the surface. Meanwhile, PEC stability of the heterojunction is increased to 77 % from 62 % stemmed from desulphurization role of NiCoP protective layer, that is extremely higher than 44 % of ZnFe 2 O 4 . The prime PEC sulfur oxidization reaction kinetics are displayed by ZnFe 2 O 4 /ZnIn 2 S 4 /NiCoP with charge transfer efficiency improved to 22.70 % from 2.45 %. Hence, sulfur oxidization photocurrent density of ZnFe 2 O 4 is enhanced to 3.44 mA/cm 2 from 0.27 mA/cm 2 with light absorption edge of 558 nm. This work not only demonstrates the highest reported PEC H 2 S splitting performance but also provides a universal design framework-combining bandgap engineering with surface state modulation—for developing robust photoelectrodes in toxic gas valorization systems.