Functional group scission-induced lattice strain in chiral macromolecular metal-organic framework arrays for electrocatalytic overall water splitting

Abstract

Electrocatalytic overall water splitting (OWS) to produce hydrogen and oxygen is one of the most advantageous ways to match the carbon-neutral concept in sustainable hydrogen production. Herein, we report a novel non-precious metal bifunctional electrocatalyst, chiral macromolecular metal-organic frameworks with lattice strain on nickel foam (LS-CMMOFs/NF), by replacing di-sulfonic acid with mono-sulfonic acid for effective and controlled introduction of lattice strain. Under alkaline conditions, LS-CMMOFs/NF at 6% lattice expansion (6%LS-CMMOFs/NF) have the best catalytic performances for oxygen evolution reaction (OER), hydrogen evolution reaction (HER) and OWS, the activity of the catalyst is significantly improved compared with that of the original CMMOFs/NF (O-CMMOFs/NF). The 6%LS-CMMOFs/NF deliver tiny overpotentials of 100 mV (HER), 137 mV (OER), total voltages of 1.467 V (OWS) at 10 mA cm−2 and maintain100-hours excellent stability. Noteworthy, the OER can reach 500 mA cm−2, with promising industrial applications. Catalytic mechanism studies, such as operando Raman, operando FTIR and density functional theory calculations indicate that lattice strain effectively enables electrons to pass through Ni/Co 3d-O 2p-Fe 3d more rapidly, thus optimizing metal 3d orbitals, which in turn activates the active surface species (Ni/Co-OOH for OER and Ni/Co-N for HER) and ultimately increases the electrocatalytic activity.