C₃N₄/PDA S‐Scheme Heterojunction with Enhanced Photocatalytic H₂O₂ Production Performance and Its Mechanism

Abstract

Developing a high‐performance photocatalyst is important for realizing efficient photocatalytic H2O2 generation. Herein, a novel step‐scheme (S‐scheme) heterojunction photocatalyst C3N4/PDA (CNP) comprised of ultrathin g‐C3N4 (U‐CN) and polydopamine (PDA) is constructed by in situ self‐polymerization. The optimal photocatalyst presents an excellent H2O2 production rate of 3801.25 µmol g−1 h−1 under light irradiation, which is about 2 and 11 times higher than that of pure U‐CN and PDA, respectively, and exceeds most of the reported C3N4‐based photocatalysts. The improvement of photocatalytic activity is ascribed to the synergistic effect of improved light absorption and promoted charge separation and transfer induced by the S‐scheme heterojunction. In situ irradiated X‐ray photoelectron spectroscopy (ISI‐XPS) reveals that the charge transfer route matches the S‐scheme mechanism. Rotating disk electrode (RDE) measurements and electron spin resonance (ESR) spectroscopy verify that H2O2 is produced by a two‐step one‐electron process. This work highlights a promising method to construct high‐performance S‐scheme heterojunction photocatalysts through the hybridization of PDA and C3N4.

Highly efficient photocatalytic H2O2production in microdroplets: accelerated charge separation and transfer at interfaces

“…À + e À + 2H + -H 2 O 2 ) or a direct one-step two-electron reduction of O 2 (O 2 + 2e À + 2H + -H 2 O 2 ). 9 Most of the research works on H 2 O 2 photosynthesis are trying to improve catalytic efficiency by modifying existing photocatalysts or developing new catalysts (e.g., metal oxides, 4 organic polymers, 10 metal-organic frameworks, 11 and covalent organic framework 12 ). However, photocatalytic H 2 O 2 production in most photocatalysis systems is still at the quite low level, far from the viability for practical application, 2,[13][14][15] which might be mainly due to the following two interdependent aspects: limited electron-hole pair separation efficiency (Z sep ) and sluggish semiconductor/solution interface charge transfer efficiency (Z trans ).…”

Review of S-Scheme Heterojunction Photocatalyst for H₂O₂ Production

“…10A-D). The loss of electrons for g-C3N4 and the accumulation of electrons for ZnO confirm Reproduced with permission 75 . Copyright 2022, Wiley-VCH.…”

“…Therefore, it is important to improve the efficiency of photocatalytic production of H2O2 by constructing S-scheme heterojunction that could well overcome the shortcomings of g-C3N4. For example, Wang et al 75 successfully developed the novel S-scheme composite system of g-C3N4/PDA (CNP) by combining ultrathin g-C3N4 (U-CN) and polydopamine (PDA) through in situ self-polymerization. In situ irradiated X-ray photoelectron spectroscopy (ISI-XPS) indicates that the carrier transmission process for prepared photocatalytic system is in accordance to the mechanism of S-scheme heterojunction.…”

Enhanced photocatalytic degradation of tetracycline by a H2O2-assisted Bi3NbO7/Bi2Sn2O7 composite under visible light

“…In general, the smaller the Nyquist radius, the higher the carrier separation efficiency of the catalyst. [48][49][50] Compared to those of the single BNO and BSO materials, the Nyquist radius of the 15% BNO/BSO composite material is the smallest, indicating its lowest impedance and highest charge separation efficiency.…”