Dafeng Zhang,Ruiqi Zhang,Junchang Liu,Xipeng Pu,Peiqing Cai
Photocatalytic H 2 evolution technique has been proved to be one of the promising approaches to overcome the present energy and environmental issues caused by the combustion of fossil fuel. Constructing heterojunction can realize the efficient separation and migration of charges and thus achieve enhanced H 2 evolution performance. Herein, we designed and prepared a ZnIn 2 S 4 /BiFeO 3 heterojunction photocatalyst with a 3D/2D structure via an ultrasonic self-assembly process. The typical 3D/2D structure with intimate interface was obtained, which not only provided more active sites but also boosted the migration of photogenerated charges. The optimal mass ratio of BiFeO 3 in ZnIn 2 S 4 /BiFeO 3 was determined to be 10%, and a 10.5-fold increase in H 2 evolution rate in comparison with of pure ZnIn 2 S 4 was achieved. Furthermore, the ZnIn 2 S 4 /BiFeO 3 composite exhibited excellent recyclability and structural stability based on cycling experiment. A S-scheme heterojunction mechanism was revealed according to the experimental results of photocatalytic H 2 evolution and electrochemical tests.
An emerging approach that employs both light and vibration energy on binary photo-/piezoelectric semiconductor materials for efficient hydrogen (H 2 ) evolution has garnered considerable attention. ZnIn 2 S 4 (ZIS) is recognized as a promising visible-light-activated photocatalyst. However, its effectiveness is constraint by the slow separation dynamics of photoexcited carriers. Density functional theory (DFT) predictions have shown that the integration of piezoelectric BiFeO 3 (BFO) is conducive to the reduction of the H 2 adsorption free energy (ΔG H* ) for the photocatalytic H 2 evolution reaction, thereby enhancing the reaction kinetics. Informed by theoretical predictions, piezoelectric BFO polyhedron particles were successfully synthesized and incorporated with ZIS nanoflowers to create a ZIS/BFO heterojunction using an ultrasonic-assisted calcination method. When subjected to simultaneous ultrasonic treatment and visible-light irradiation, the optimal ZIS/BFO piezoelectric enhanced (piezo-enhanced) heterojunction exhibited a piezoelectric photocatalytic (piezo-photocatalytic) H 2 evolution rate approximately 6.6 times higher than that of pristine ZIS and about 3.0 times greater than the rate achieved under light-only conditions. Moreover, based on theoretical predictions and experimental results, a plausible mechanism and charge transfer route for the enhancement of piezo-photocatalytic performance were studied by the subsequent piezoelectric force microscopy (PFM) measurements and DFT calculations. The findings of this study strongly confirm that both the internal electric field of the step-scheme (S-Scheme) heterojunction and the alternating piezoelectric field generated by the vibration of BFO can enhance the transportation and separation of electron-hole pairs. This study presents a concept for the multipath utilization of light and vibrational energy to harness renewable energy from the environment.
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