Enhanced overall water splitting by morphology and electronic structure engineering on pristine ultrathin metal-organic frameworks

Abstract

Metal-organic frameworks (MOFs) have caused extensive attention attributed to their widespread applications including electrocatalysis by virtue of their distinctive structural characteristics. However, the direct application of pristine MOFs as bifunctional electrocatalysts is quite challenging due to their insufficient active sites and poor electrical conductivity. In this research, the ultrathin tri-metal (Fe, Co, and V) doped FeCoV-NiMOF nanosheet arrays were prepared through a facile hydrothermal method. Benefiting from the distinctive ultrathin (1.5 nm) nanosheet arrays and electronic structure reconfiguration induced by heteroatom doping, the prepared FeCoV-NiMOF displays the low overpotentials of 238, 309, and 408 mV for oxygen evolution reaction (OER) and 144, 255, and 349 mV for hydrogen evolution reaction (HER) at the current densities of 10, 100, and 1000 mA cm⁻², respectively, outperforming the vast majority of previously reported bifunctional pristine MOFs. The electrolytic cell utilizing FeCoV-NiMOF as both cathode and anode requires just 1.61 V to attain 10 mA cm⁻² and displays superior stability of 100 h at 100 mA cm⁻². In the anion exchange membrane electrolyzer, as-prepared FeCoV-NiMOF needs a low cell voltage of 2.16 V at 500 mA cm⁻² for effective overall water splitting, demonstrating its substantial potential as bifunctional electrodes for H₂ production. The viable and efficient strategy in this study exhibits great prospects to enrich the exploration of bifunctional MOF-based electrocatalysts with superior performance for renewable energy conversion.