TM-N4 doped in 4,6,8-biphenylene as an efficient trifunctional electrocatalyst for oxygen reduction reaction, oxygen evolution reaction and hydrogen evolution reaction

Multifunctional catalysts for oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are beneficial to improve the energy efficiency of water decomposition systems, metal-air batteries, etc., and bring hope to solve the current problems of energy shortage and environmental pollution. Due to the low cost and good tunability, doping transition metals (TMs) on carbon-based materials as single-atom catalysts (SACs) is a hot research topic. In this paper, a novel structure is constructed based on 4,6,8-biphenylene (TM-N4-C468, TM = 3d transition metals), and investigate its catalytic activity for ORR/OER/HER by using first principles. The results showed that Fe-N4-C468 is an excellent trifunctional catalyst for ORR, OER and HER, and Co-N4-C468 is expected to become an efficient OER/HER bifunctional electrocatalyst. However, in the solvent environment, the ORR activity of Fe-N4-C468 was significantly enhanced, while the OER activity of Co-N4-C468 was worse and no longer suitable as a bifunctional catalyst. Finally, the origin of the catalytic activity of TM-N4-C468 is analyzed using the d-band center, Crystal Orbit Hamilton Population (COHP) and the molecular orbitals theory (MOs) of Fe-N4-C468. This work proves that Fe-N4-C468 is an excellent trifunctional electrocatalyst, and provides a direction for the experimental preparation of low-cost multifunctional single-atom catalysts.