Regulation of eg orbital occupancy in Ni-based metal-organic frameworks for efficient hydrogen peroxide electrosynthesis

Abstract

Subject to the binding strength between the cathode and the oxo-intermediates, the hydrogen peroxide (H2O2) electrosynthesis with high productivity and high selectivity in oxygen reduction reaction (ORR) cannot be achieved simultaneously. In this work, the dual-metal-organic frameworks (NiFe-MOFs) is designed and synthesized, in which the eg orbital occupancy of Ni nodes is regulated by the super-exchange effect of Ni(2+σ)+-O-Fe(3-σ)+ bond. As a result, the binding strength between the cathode and the oxo-intermediates (*O2, *OOH) is optimized, which efficiently promotes oxygen reduction kinetics and inhibits O-O bond breakage. The H2O2 yield of NiFe-MOFs cathode reaches 1.83 mol·g−1·h−1 with a Faraday efficiency of 96.3 % at 0.5 V vs. RHE, which is far superior to Ni-MOFs (0.21 mol·g−1·h−1, 65.4 %), Fe-MOFs (0.65 mol·g−1·h−1, 57.5 %). This work offers a new strategy to design and develop cathodic catalysts for H2O2 electrosynthesis with high productivity and high selectivity.