Pyroelectric Photocatalysis: Polarization mechanism insight, in situ characterizations and challenges

Photocatalysis, in which semiconductors are used to harvest light and produce charge carrier derivatives, has been widely valued as a promising sustainable technique. However, due to the poor separation efficiency of photogenerated electron-hole pairs, the overall energy conversion efficiency sticks at 1%, which is far from the desired industrial application demand of 10%. Very recently, pyroelectric catalysis technology with asymmetric positive/negative charge centers has emerged, which is hoped to play a key role in alleviating energy crisis and environmental problems. With pyroelectric catalysts introduced into photocatalysts, its internal spontaneous polarization electric field can effectively promote the separation of photogenerated carriers, thus improving the photocatalytic performance. Therefore, pyroelectric photocatalysis is expected to break the widely recognized energy efficiency threshold of 10% for scale-up industrial implementation of photocatalytic technique. Nevertheless, there is still a huge cognitive gap between fundamental theory and practice in the design, characterizations, and application of pyroelectric photocatalysts. Hence, a comprehensive review is conducted to understand the state-of-the-art progress in pyroelectric photocatalysis. The polarization treatment, evaluation parameters and the corresponding atomic force microscopy and X-ray diffraction characterization for the identification of high-efficiency pyroelectric materials are also elaborated. We also propose five potential directions for large-scale applications of pyroelectric photocatalysis, including multi-step cascade reactions, controllable reactions, excitable biomaterials, hazardous waste treatment, and water wave energy collection devices.