Sulfur-mediated photodeposition synthesis of NiS cocatalyst for boosting H2-evolution performance of g-C3N4 photocatalyst

Modification of nickel sulfide cocatalysts is considered to be a promising approach for efficient enhancement of the photocatalytic hydrogen production performance of g-C3N4. Providing more NiS cocatalyst to function as active sites of g-C3N4 is still highly desirable. To realize this goal, in this work, a facile sulfur-mediated photodeposition approach was developed. Specifically, photogenerated electrons excited by visible light reduce the S molecules absorbed on g-C3N4 surface to S2−, and subsequently NiS cocatalyst is formed in situ on the g-C3N4 surface by a combination of Ni2+ and S2− due to their small solubility product constant (Ksp = 3.2 × 10−19). This approach has several advantages. The NiS cocatalyst is clearly in situ deposited on the photogenerated electron transfer sites of g-C3N4, and thus provides more active sites for H2 production. In addition, this method utilizes solar energy with mild reaction conditions at room temperature. Consequently, the synthesized NiS/g-C3N4 photocatalyst achieves excellent hydrogen generation performance with the performance of the optimal sample (244 μmol h−1 g−1) close to that of 1 wt% Pt/g-C3N4 (316 μmol h−1 g−1, a well-known excellent photocatalyst). More importantly, the present sulfur-mediated photodeposition route is versatile and facile and can be used to deposit various metal sulfides such as CoSx, CuSx and AgSx on the g-C3N4 surface, and all the resulting metal sulfide-modified g-C3N4 photocatalysts exhibit improved H2-production performance. Our study offers a novel insight for the synthesis of high-efficiency photocatalysts.