A research group led by Prof. WAN Yinhua from the Institute of Process Engineering of the Chinese Academy of Sciences has developed a catalyst with dual photocatalytic and biomimetic catalytic activity for the production of hydrogen peroxide (H₂O₂). The strategy involves loading gold nanoparticles (AuNPs) onto graphite carbon nitride (GCN) nanosheets using polyethyleneimine (PEI) as a "bridge." The study was published in Chemical Engineering Journal. 

Solar-driven photocatalysis is a promising alternative strategy for H₂O₂ production, and GCN is a popular choice in the field of photocatalysis due to its straightforward synthesis, cost-effectiveness, stable physical and chemical properties, and broad light absorption spectrum. However, GCN nanosheets alone have limited performance in photocatalytic H₂O₂ production in pure water due to the high energy barrier of water dissociation and low separation efficiency of charge carriers. 

Hole sacrificial agents (acting as electron donors) such as ethanol, isopropanol, and benzyl alcohol are commonly used to improve the selectivity of oxygen reduction. However, the addition of organic agents has adverse environmental impacts, which is not conducive to the sustainability of H₂O₂ production. Therefore, it is crucial to engineer a GCN material with enhanced electron-hole pair separation efficiency to facilitate water oxidation and oxygen reduction. 

"Inspired by photo-enzyme-coupled catalytic system in chloroplasts, we developed a composite catalyst by loading AuNPs (enzyme mimics) on GCN (photocatalyst) nanosheets using PEI as the "bridge" (PEI-GCN/Au)," Prof. WAN said. 

The introduction of PEI and AuNPs helps adjust the electronic structure of GCN, facilitating the rapid separation of photogenerated carriers. The surface plasmon resonance of AuNPs, when excited by incident light, promotes the activation of glucose molecules, elevating their reactivity with O₂ and improving the glucose oxidase-mimicking catalytic production of H₂O₂. The grafting of PEI and the addition of glucose enhance the O₂ adsorption on the catalyst surface.  

The PEI-GCN/Au composite demonstrates exceptional H₂O₂ production efficiency (270 μmol g^-1 h^-1) under visible light irradiation, using only glucose, H₂O and O₂ as reactants. As a result, both the biomimetic catalytic and photocatalytic reduction of O₂ to H₂O₂ are enhanced, achieving a significant synergistic enhancement effect of 175%. 

"This work establishes a paradigm of coupling biomimetic catalysis and photocatalysis for co-production of chemicals. It not only provides insights into the development of materials for efficient H₂O₂ production, but also introduces an innovative concept for integrating biocatalysis and photocatalysis," said Prof. LUO Jianquan, the corresponding author of this study.  

The proposed mechanism for the H₂O₂ production by PEI-GCN/Au biomimetic-photo-coupled catalysis. (Image by ZHANG Huiru)