Tailoring Heteroatoms in Conjugated Microporous Polymers for Boosting Oxygen Electrochemical Reduction to Hydrogen Peroxide
Zhongjie Yang, Yang Gao, Lulu Zuo, Chang Long, Caoyu Yang, Xiaofei Zhang
Abstract
Heteroatom-doped metal-free carbon materials have been considered as efficient catalysts for electrochemical H 2 O 2 production via the two-electron oxygen reduction reaction (2e – -ORR). However, it is difficult to construct the precise heteroatom-doped carbon materials driving the 2e – -ORR process through the conventional pyrolytic method. Reported here is a diatomic hetero-cyclization strategy to construct efficient 2e – -ORR catalysts based on poly-benzimidazole, poly-benzoxazole, and poly-benzothiazole (PBXs, X = I, O, and T), which are composed of N-NH-, N-O-, or N-S-heterocycles, respectively. Poly-benzothiazole (PBT) with N, S-doped heterocyclic rings exhibit a higher H 2 O 2 selectivity (95.6%) over corresponding undoped imine-based polymers (21.7%) and maintain remarkable electrochemical durability, which are among the highest values for PBXs as 2e – -ORR catalysts. A maximum H 2 O 2 production rate of 3.13 mol g catalyst –1 h –1 is obtained at a fixed current density of 100 mA cm –2 . Moreover, a remarkable Faradaic efficiency (F.E.) of 96% as well as good catalyst stability maintained over 50 h of testing over the PBT catalyst in the three-phase flow cell is achieved. Density functional theory (DFT) calculations reveal that the atomic spin density distribution of the corresponding carbon active sites in PBXs contributes to the high electrochemical performance in the 2e – -ORR process. These results thus present that atomic-scale doping of sulfur atoms will strongly boost H 2 O 2 production via affecting adjacent carbon atoms.