Modulating the Molecular Structure of Graphitic Carbon Nitride for Identifying the Impact of the Piezoelectric Effect on Photocatalytic H₂O₂ Production

Abstract

The use of the piezoelectric effect for regulating the separation and transportation of charge carriers in the artificial photosynthesis of H 2 O 2 has been established as a promising approach. However, an in-depth and comprehensive understanding of the piezoelectric effect on photocatalysis is still far from satisfactory. Herein, we have accurately modulated the molecular structure of graphitic carbon nitride (CN) to investigate the effect of piezoelectricity on photocatalytic H 2 O 2 production over CN. Our results show that the role of the piezoelectric effect in photocatalytic H 2 O 2 production over CN strongly depends on the molecular structure of CN. Specifically, for CN, CN modified by phosphorus (CN-P), oxygen-functionalized CN (CN-OF), and cyano-groupgrafted CN (CN-CA), the photocatalytic activity of CN, CN-P, and CN-OF is enhanced by approximately 1.40, 1.46, and 1.51 times due to the piezoelectric effect, respectively, while the photocatalytic activity of CN-CA is decreased by 6.0 times. To clarify and understand the key factors affecting piezo-photocatalysis activity, we employed density functional theory, photo-electrochemical measurements, and piezoresponse force microscopy measurements to explore active sites, piezoelectric polarization, and charge separation over molecular-functionalized CN. Our results reveal that the impact of the piezoelectric effect on photocatalytic H 2 O 2 production over CN results from the comprehensive influence of multiple factors. This work not only demonstrates that the molecular structure of CN determines whether the piezoelectric effect improves photocatalytic H 2 O 2 production over CN but also unveils the mechanism of the piezoelectric effect on photocatalytic H 2 O 2 production over CN.

Recent Advancement in Piezopolarization Induced Photocatalytic H2O2 Production: Fundamentals, Theoretical Insights, and Future Endeavors

“…In this regard, Wang et al explored the piezo-photocatalytic H 2 O 2 evolution activity of g-C 3 N 4 by modulating the structure of the parent material. Figure a–c displays the photocatalytic, piezocatalytic, and piezo-photocatalytic H 2 O 2 production for CN, CN-P, CN-OF, and CN-CA specimens, respectively.…”

“…(f) Schematic representation of underlying H 2 O 2 production mechanism over the designed material in piezo-photocatalysis. Reproduced from ref . Copyright 2023 American Chemical Society.…”

“…In another case, using DFT study, Wang et al uncovered the mechanism of the piezo-induced photocatalytic H 2 O 2 evolution of g-C 3 N 4 (CN) by modulating the molecular structure with phosphorus (CN-P), functionalizing with oxygen (CN-OF), and grafting with a cyano group (CN-CA). The team calculated the reaction energy profiles of the designed materials (Figure a) and observed a minimum energy barrier (0.22 eV) for CN-CA catalyst compared to the other materials, which is in good agreement with the highest catalytic activity.…”

“…Mapping of charge density difference between H 2 O 2 and active sites: (b) CN and (c) CN-CA; the sky-blue (negative charge region) and yellow (positive charge region) colors are O-surfaces. Reproduced from ref . Copyright 2023 American Chemical Society.…”

Spaced Double Hydrogen Bonding in an Imidazole Poly Ionic Liquid Composite for Highly Efficient and Selective Photocatalytic Air Reductive H2O2 Synthesis

“…Till now, there have been some cases investigating the photocatalytic performance of direct air reductive H 2 O 2 . [5] Despite the numerous efforts devoted to improving O 2 adsorption, such as defect or doped sites, [6] heteroatom incorporation, [7] edge active sites, [8] and molecular structure modulation, [9] the determination of the specific active site to simultaneously selectively capture O 2 from the air and converting O 2 into H 2 O 2 has not been documented so far. Therefore, the activity under the air is still far from that of the pure O 2 supply in the same photocatalytic system.…”