Li Li,Kaixuan Kuang,Xiuzhen Zheng,Jiahui Wang,Wei Ren,Jingbiao Ge,Sujuan Zhang,Shifu Chen
To enhance the efficiency of photocatalytic H 2 evolution, numerous methods are employed by increasing the utilization of photogenerated charge carriers (PCCs), including catalyst design, defect regulation, and selection of suitable H + resources. Using self-assembly method, CoWO 4 /Zn x Cd 1−x S with p–n heterojunction was synthesized. Although CoWO 4 (CW) cannot produce H 2 under visible light irradiation, it can provide photogenerated electrons (e − ) to Zn 0.3 Cd 0.7 S (ZCS), and largely increase the photocatalytic activity of ZCS. The optimal CW/ZCS composite can reach 15.58 mmol·g −1 ·h −1 , which is 45.8 and 24.3 times higher than the values of the pure CdS and ZCS, respectively. The largely enhanced photocatalytic H 2 production is attributed to the Zn vacancies (V Zn ), p–n heterojunction, and p-chlorobenzyl alcohol (Cl–PhCH 2 OH) as the H + source of H 2 production. V Zn on the ZCS surface as the capture center of photogenerated holes (h + ), can regulate the carrier distribution, which results in more photogenerated e − and less generated h + . The combination of p–n heterojunction and V Zn can enhance the separation and transfer efficiency of PCCs, and effectively inhibit the recombination of charge carriers. To further improve the utilization rate of PCCs, the photocatalytic H 2 evolution is proceeded by Cl–PhCH 2 OH oxidation in N , N -dimethylformamide solution, with 4-chlorobenzaldehyde (Cl–PhCHO) generated. The separated photogenerated e − and h + both participated in the redox reaction of H + reduction and Cl–PhCH 2 OH oxidation, considering that the amount of H 2 and Cl–PhCHO products are close to 1:1. This work not only facilitates the separation and transfer of PCCs, but also provides directions for the design of efficient photocatalysts and H 2 evolution in the organic phase.
To improve the efficiency of photocatalytic H 2 production, many researches are widely studied on the microstructure regulation of cocatalysts, including morphology design, atomic doping, and heterostructures composite. Derived from Ni-Co MOF materials, hollow NiCoP (NCP) microspheres as electron acceptor can effectively promote the separation of photogenerated charge carriers (PCCs). With Zn 0.3 Cd 0.7 S (ZCS) nanoparticles supporting on the surface of NCP, a series of NiCoP/Zn 0.3 Cd 0.7 S (NCP/ZCS) composites were successfully prepared by electrostatic self-assembly and characterized by many tests. Under visible light illumination, 10 % NCP/ZCS catalyst had the best H 2 production rate (21.50 mmol g −1 h −1 ) with benzyl alcohol (PhCH 2 OH) as the sacrificial agent, about 45.74 times that of pure ZCS. Its apparent quantum yield (AQY) reached highest at 400 nm, which was about 18.94 %. Through a combination of photoelectric, PL and UPS experiments, a Z-scheme transfer model was proposed in the NCP/ZCS composite for highly efficient photocatalytic H 2 generation. For ZCS, the hollow structure of the NCP cocatalyst can improve the light utilization rate, increase the reaction active site and accelerate the electron transmission rate. This structural design of cocatalyst not only provides a new idea to understand the reaction process of photocatalysis, but also opens up new directions for the development of simple, efficient and low-cost cocatalysts.
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