A novel thiophene-linked metalloporphyrin conjugated polymer: a highly efficient trifunctional electrocatalyst for overall water splitting and oxygen reduction

Abstract

It is highly desirable to design high performance trifunctional electrocatalysts for the hydrogen evolution reaction, oxygen evolution reaction, and oxygen reduction reaction (HER/OER/ORR). Herein, we designed a thiophene-linked porphyrin (TP) conjugated polymer that serves as a substrate for anchoring single transition metal atoms (TM–N₄/TP) employed in the HER, OER and OER by density functional theory (DFT) calculations. It is demonstrated that TM atoms can be stably anchored onto TP and exhibit excellent electrochemical stability. Notably, Co–N₄/TP exhibits an overpotential (η) of 0.07 V for the HER, following the Volmer–Heyrovsky mechanism with an ultralow energy barrier of 0.15 eV under acid conditions. Meanwhile, Co–N₄/TP demonstrates low η for both the OER and ORR, with η_OER/η_ORR = 0.24/0.42 V, which is comparable to those of the noble-metal benchmark catalysts for the OER and ORR. Therefore, Co–N₄/TP emerges as a trifunctional catalyst for overall water splitting and oxygen reduction. The oxidation state and magnetism of metal atoms were demonstrated to correlate with the catalytic activity on TM–N₄/TP. Machine learning (ML) analysis indicates that the d band center (ε_d) is the most crucial feature for HER activity on TM–N₄/TP. Moreover, it was observed that OER or ORR activity cannot be determined by a sole descriptor, and the feature importance is tunable in the OER or ORR process. This work highlights a novel family of highly efficient multifunctional catalysts for renewable energy applications based on thiophene-linked metalloporphyrin conjugated polymers.