Internal Electric Field-Modulated S-Scheme Ni₃Se₄/TiO₂ Nanoparticle Heterojunction for Efficient Photocatalytic H₂ Evolution

Construction of an S-scheme heterojunction with staggered energy band structures can facilitate the charge separation and reserve their high redox potential. Herein, an S-scheme Ni 3 Se 4 /TiO 2 heterojunction is successfully constructed via an in situ hydrothermal method. The introduction of the Ni 3 Se 4 nanoparticle can enhance the light absorption ability, favor the charge transfer, and induce more abundant electrochemically active sites of the composite. Based on the photocatalytic H 2 evolution experiments, the H 2 evolution rate of 10%-Ni 3 Se 4 /TiO 2 reaches 8409.3 μmol · g –1 · h –1 under simulated sunlight irradiation using TEOA as the sacrificial agent, which is 32.3 and 127.2 times than those of TiO 2 and Ni 3 Se 4, respectively. This composite also exhibits excellent stability during four cycling tests. In addition, the charge transfer between Ni 3 Se 4 and TiO 2 following the S-scheme route is confirmed by the core-level alignment analysis and hydroxyl radical capture tests; this special charge transfer can retain the active charges by consuming the inactive electrons and holes. This work demonstrates that the Ni 3 Se 4 nanoparticle as a reduction photocatalyst can be employed to construct an S-scheme heterojunction with desired photocatalytic performance.