One-pot photochemical synthesis of amorphous NiSx-modified CdxZn1-xS for direct photocatalytic hydrogen evolution
Traditional photocatalysts are usually prepared in first-pot and then dried, and re-dispersed in the second-pot for photocatalytic H 2 generation, where the two-pot mode may lead to loss/underutilization of active sites. To maximize active sites, herein we propose in-situ synthesis and photocatalytic hydrogen (H 2 ) evolution in one-pot mode. NiS x -modified Cd x Zn 1-x S (NiS x -CZS) photocatalysts as a model are prepared by photochemical reactions of metal salt precursors in the presence of sulfur. Among NiS x -CZS photocatalysts, 2 wt% NiS x -CZS exhibits the strongest photoabsorption in the visible region and the highest photocurrent response, implying that it produces the most photoexcited electrons under visible light irradiation. When irradiated by visible light (≥ 420 nm), the in situ H 2 generation rate of optimized 2 wt% NiS x -CZS with higher concentration of active sites is 17.98 mmol g -1 h -1 (one-pot mode), which is better than the two-pot mode (15.08 mmol g -1 h -1 ). Besides, the presence of in situ attached NiS x co-catalyst on CZS host results in a 22.2-fold H 2 production rate compared to pristine CZS. H 2 production performance with NiS x co-catalyst (89.92 mmol g -1 ) within 5 h is also better than noble/transitional metals as co-catalysts (9.62-26.99 mmol g -1 ). The amorphous NiS x provide sufficient unsaturated edge sulfur (S) sites, which serve as active centers to capture and enrich H + and lead to the expedited H 2 generation through the effective combination of H ads atoms. This work provides a unique insight into the one-pot photochemical synthesis of photocatalysts with charge-accumulated active sites and a rational strategy for in situ hydrogen production.
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