A direct Z-scheme NiCo 2 O 4 /ZnIn 2 S 4 heterojunction for highly efficient visible-light-driven H 2 evolution.

Exploiting efficient and stable photocatalysts is the primary goal of photocatalytic water splitting for H 2 production. In this work, a sea urchin-like bimetallic NiCo 2 O 4 -decorated ZnIn 2 S 4 heterojunction was fabricated via a solvent evaporation method. Investigation shows that the introduction NiCo 2 O 4 can expand the UV-vis absorption range, enhance the absorption intensity, promote the charge separation, decrease the charge transfer resistance, induce more active sites, and decrease the H 2 evolution overpotential of the composite. Besides, the charge transfer between NiCo 2 O 4 and ZnIn 2 S 4 follows a Z-scheme route based on the ˙OH radical capture experiments; this can preserve the strong oxidation-reduction reaction ability of photogenerated electrons and holes, leading to a faster H 2 evolution rate, which reaches 17.28 mmol g -1 h -1 over the 4.8%-NiCo 2 O 4 /ZnIn 2 S 4 composite under 300 W Xe lamp irradiation in 20 vol% triethanolamine (TEOA) solution and is 3.0 times higher than that of ZnIn 2 S 4 . In addition, NiCo 2 O 4 /ZnIn 2 S 4 also has excellent stability during 5 consecutive cycles. This work provides an effective method for constructing a highly effective Z-scheme heterojunction system for photocatalytic H 2 production.