Computational screening of two-dimensional coordination polymers as efficient catalysts for oxygen evolution and reduction reaction

Oxygen evolution and reduction reactions (OER and ORR) are essential to the development of renewable energy conversion and storage technologies. For the first time, we investigate newly experimentally realized two-dimensional hexaaminobenzene-based coordination polymers (2D HAB-CPs) as OER and ORR catalysts through computational screening approach. We find that the interaction strength between intermediates and the transition metal complex (TM-N₄) govern the catalytic activity of 2D HAB-CPs for OER and ORR. The interaction strength is strongly contingent on d-band centers, which can be modulated by changing TM atoms with different d-electron occupations. This modification of the interaction strength allows us to screen out the catalyst with the best catalytic performance. The best catalyst for OER is 2D Rh-HAB-CP with an over-potential (η) of 0.32 V, followed by Co-HAB-CP (0.41 V), while for ORR, Fe-HAB-CP has a smallest maximum free energy change (ΔG_max^1.23) of 0.52 eV under equilibrium potential. Furthermore, these results inspire us to design a bifunctional OER/ORR catalyst by mixing Fe/Co precursors in 2D HAB-CP with the ORR/OER theoretical overpotentials even lower than that of the best ORR/OER catalysts (Pt/RuO₂). In addition, all the 2D HAB-CPs are metallic due to the effects of d-p-π conjugation, which ensures fast electron transfer during the electrochemical reactions. Our findings highlight a new family of 2D materials as efficient non-precious-metal metal-air battery catalyst and offer a novel strategy in catalyst design.