Developing Ni single-atom sites in carbon nitride for efficient photocatalytic H₂O₂ production

• Main Authors: Zhang, Xu, Su, Hui, Cui, Peixin, Cao, Yongyong, Teng, Zhenyuan, Zhang, Qitao, Wang, Yang, Feng, Yibo, Feng, Ran, Hou, Jixiang, Zhou, Xiyuan, Ma, Peijie, Hu, Hanwen, Wang, Kaiwen, Wang, Cong, Gan, Liyong, Zhao, Yunxuan, Liu, Qinghua, Zhang, Tierui, Zheng, Kun
• Other Authors: School of Chemistry, Chemical Engineering and Biotechnology
• Format: Article
• Language: English
• Published: 2024
• Subjects: Chemistry; Atomic absorption spectroscopy; Hydrogen peroxide
• Online Access: https://hdl.handle.net/10356/173861
• Institution: Nanyang Technological University

Photocatalytic two-electron oxygen reduction to produce high-value hydrogen peroxide (H2O2) is gaining popularity as a promising avenue of research. However, structural evolution mechanisms of catalytically active sites in the entire photosynthetic H2O2 system remains unclear and seriously hinders the development of highly-active and stable H2O2 photocatalysts. Herein, we report a high-loading Ni single-atom photocatalyst for efficient H2O2 synthesis in pure water, achieving an apparent quantum yield of 10.9% at 420 nm and a solar-to-chemical conversion efficiency of 0.82%. Importantly, using in situ synchrotron X-ray absorption spectroscopy and Raman spectroscopy we directly observe that initial Ni-N3 sites dynamically transform into high-valent O1-Ni-N2 sites after O2 adsorption and further evolve to form a key *OOH intermediate before finally forming HOO-Ni-N2. Theoretical calculations and experiments further reveal that the evolution of the active sites structure reduces the formation energy barrier of *OOH and suppresses the O=O bond dissociation, leading to improved H2O2 production activity and selectivity.