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

The electrocatalytic oxygen reduction reaction via atwo-electronpathway (2e(-) ORR) is a promising route for hydrogenperoxide (H2O2) production. However, the strongelectron interaction between the metal site and oxygen-containingintermediates usually generates 4-electron ORR, limiting H2O2 selectivity. Here, combining theoretical and experimentalstudies, we propose to enhance the electron confinement of the indium(In) center in an extended macrocyclic conjugation system toward high-efficiencyH(2)O(2) production. The extended macrocyclic conjugationin indium polyphthalocyanine (InPPc) evokes the attenuated transferelectron ability of the In center and weakens the interaction betweenthe s orbital of In and the p obital of OOH*, favoring protonationof OOH* to H2O2. Experimentally, the preparedInPPc catalyst exhibits a noticeable H2O2 selectivityabove 90% in 0.1-0.6 V vs RHE, outperforming the counterpartInPc. Importantly, the InPPc displays a high average H2O2 production rate of 23.77 mg/cm(2)/h in a flowcell. This study proposes a novel strategy to engineer molecular catalystsand provides new insights into the ORR mechanism.

Automated summary

In this study, the authors propose a novel strategy to enhance the electron confinement of the indium center in an extended macrocyclic conjugation system for high-efficiency H2O2 production. The prepared InPPc catalyst exhibits a remarkable H2O2 selectivity above 90% and a high average H2O2 production rate of 23.77 mg/cm(2)/h in a flow cell. This study provides new insights into the ORR mechanism and offers a promising route for H2O2 production.