Wen He,Qianxiang Xiao,Zhenglemei Qiu,Feng He,Qixu Chen,Lijun Hu,Hongqing Wang
Photocatalysis has been applied to the reduction of U(VI), but how to improve the separation of photogenerated carriers, realize photocatalysis without sacrificial agents, and still have a certain catalytic activity in the absence of light are still problems that need to be solved. In this paper, a series of Zn x Cd 1-x S (0 ≤ x ≤ 1) solid solutions with different Zn/Cd molar ratios are synthesized for piezo-photocatalytic reduction of U(VI) under air atmosphere and without the addition of sacrificial agent. Under combined visible light and ultrasound irradiation, the homojunction with bicrystalline structure, i.e., wurtzite (WZ) and zinc-blende (ZB) formed from Zn 0.7 Cd 0.3 S solid solution , provides effective space charge separation and exhibits a prominently synergetic piezo-photocatalytic U(VI) removal rate of 99.3 % for 15 min, which is 34.2 times higher than that of ultrasound alone (2.9 % in 15 min) and 1.2 times greater than that of light alone (80.7 % in 15 min). Meanwhile, the charge transfer in Zn 0.7 Cd 0.3 S homojunction was revealed in this study through DFT calculations and a mechanism for the piezo-photocatalytic synergistic reduction of U(VI) was proposed. This work promises to provide a new coupled catalytic reaction design strategy for the efficient reduction of U(VI).
Ruoning Liu,Xinggen Yuan,Wenming Lu,Yunfei He,Shaoyun Shan,Jing Xu,Tianding Hu
Developing advanced photothermal effect photocatalysts to maximize solar utilization receives increasing attentions in photocatalytic H 2 production. Herein, a Ni-doped Zn 0.7 Cd 0.3 S (Ni-ZCS-20) integrating photothermal material and photocatalyst was constructed via simple one-step hydrothermal method. Successful incorporation of Ni into Zn 0.7 Cd 0.3 S was confirmed by various characterization techniques including XRD, XPS, SEM and TEM. Under photothermal-assisted condition, the Ni-ZCS-20 offered a superfast H 2 generation rate, reaching as high as 183 mmol/g·h, which exhibited enormous advantages over existing photocatalysts. Detailed mechanism explorations verified that such a high H 2 generation rate of Ni-ZCS-20 could be attributed to the lowed H 2 generation overpotential, broadened light absorption region, and promoted photogenerated carrier separation originating from the Ni doping. In addition, the doped Ni partly substituted the Zn in Ni-ZCS-20, providing an extra channel for photogenerated electrons and efficiently hindering the recombination of electron-hole pairs. Density functional theory (DFT) calculations demonstrated that Ni incorporation into ZCS effectively tailored its electronic structure, enhanced surface electron-supply capability, and optimized hydrogen adsorption, thereby leading to superior catalytic performance of Ni-ZCS toward HER. This finding provides valuable guidance for constructing photothermal effect materials to exploit full spectrum solar in photocatalytic H 2 evolution.
Wen He,Qianxiang Xiao,Haiyan Jiang,Zhenglemei Qiu,Ziyang Chang,Feng He,Qixu Chen,Xiangke Wang,Hongqing Wang
Enhanced bulk-surface charges separation and migration are essential to maximize the photocatalytic activity. In this study, ethylenediamine (EDA)-modified Zn 0.7 Cd 0.3 S nanorods (ZCS-NR-EDA) were synthesized through an integral modification approach. After 1-hour adsorption equilibrium followed by 6-minute co-irradiation with visible light and ultrasonic waves, ZCS-NR-EDA removed 99.2 % of U(VI) from the solution, significantly better than Zn 0.7 Cd 0.3 S nanoparticles (ZCS-NP) (13.6 %) and Zn 0.7 Cd 0.3 S nanorods (ZCS-NR) (25.3 %). This catalytic performance has outperformed most reported materials. Experimental and density functional theory (DFT) calculation studies confirmed that EDA modification induced polarization to establish a bulk electric field (BEF) and modified the electron distribution at the material's surface to create localized surface electric field (LSEF), while simultaneously enhancing the material's piezoelectric properties. The synergistic effect of these triple electric fields (polarization-induced BEF, LSEF, and piezoelectric field (PF)) promoted migration of bulk-surface charges, thereby enhancing catalytic performance. When applied to uranium spiked tailing water, ZCS-NR-EDA achieved up to 98.1 % U(VI) removal within 15 min of combined visible light and ultrasonic irradiation (after adsorption equilibrium). More importantly, this “tri-electric fields synergy” strategy provides a novel approach for the design of advanced photocatalytic materials.
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