Highly hydrophilic and surface defect-rich MOF-74-PA15 obtained by phytic acid etching as a robust catalyst for the oxygen evolution reaction.

Abstract

Water splitting is an energy conversion process of vital importance. The oxygen evolution reaction (OER), as the half-reaction of water splitting, has very slow kinetics due to the complex quaternary electron transfer process involved, which greatly impedes the efficiency of energy conversion. The rational construction and modification of metal-organic frameworks (MOFs) offer a novel alternative for developing efficient OER electrocatalysts. In this study, MOF-74-PA15 with abundant surface defects and high hydrophilicity was successfully in situ constructed by etching MOFs for different reaction times using phytic acid (PA). The etching of PA increases the active area, and improves the hydrophilicity, allowing tighter contact between the material and the electrolyte. As a result, MOF-74-PA15 exhibits the most optimal OER catalytic performance in all the samples. The overpotential is 250 mV in 1 M KOH at 100 mA cm-2, with the lowest Tafel slope (35.59 mV dec-1). Furthermore, MOF-74-PA15 exhibits excellent stability. It maintains stability for 72 hours at a current density of 50 mA cm-2. This study presents a novel and feasible solution for modifying MOFs as electrocatalytic water splitting catalysts.