Enhanced Electron Confinement of p-Block Indium Site in Extended Macrocyclic Conjugation Boosting Oxygen Reduction to Hydrogen Peroxide

Yan Xu; Shanyong Chen; Long Chen; Xinwang Zhu; Xiaoqing Qiu; Min Liu

doi:10.1021/acs.jpclett.3c01500

Enhanced Electron Confinement of p-Block Indium Site in Extended Macrocyclic Conjugation Boosting Oxygen Reduction to Hydrogen Peroxide

J Phys Chem Lett. 2023 Jun 29;14(25):5850-5859. doi: 10.1021/acs.jpclett.3c01500. Epub 2023 Jun 21.

Authors

Yan Xu¹, Shanyong Chen^{1

2

3}, Long Chen¹, Xinwang Zhu¹, Xiaoqing Qiu¹, Min Liu²

Affiliations

¹ College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, P.R. China.
² Institute of Super-microstructure and Ultrafast Process in Advanced Materials, School of Physics and Electronics, Central South University, Changsha 410083, China.
³ Guangdong Key Laboratory of Environmental Pollution and Health, School of Environment, Jinan University, Guangzhou 511443, P. R. China.

PMID: 37341176
DOI: 10.1021/acs.jpclett.3c01500

Abstract

The electrocatalytic oxygen reduction reaction via a two-electron pathway (2e^- ORR) is a promising route for hydrogen peroxide (H₂O₂) production. However, the strong electron interaction between the metal site and oxygen-containing intermediates usually generates 4-electron ORR, limiting H₂O₂ selectivity. Here, combining theoretical and experimental studies, we propose to enhance the electron confinement of the indium (In) center in an extended macrocyclic conjugation system toward high-efficiency H₂O₂ production. The extended macrocyclic conjugation in indium polyphthalocyanine (InPPc) evokes the attenuated transfer electron ability of the In center and weakens the interaction between the s orbital of In and the p obital of OOH*, favoring protonation of OOH* to H₂O₂. Experimentally, the prepared InPPc catalyst exhibits a noticeable H₂O₂ selectivity above 90% in 0.1-0.6 V vs RHE, outperforming the counterpart InPc. Importantly, the InPPc displays a high average H₂O₂ production rate of 23.77 mg/cm²/h in a flow cell. This study proposes a novel strategy to engineer molecular catalysts and provides new insights into the ORR mechanism.