NiCo-Metal Organic Frameworks for Highly Stable Electrocatalytic Water Splitting under Alkaline and Neutral pH Ranges

Abstract

The advances in functional electrocatalysts for real-time production of green hydrogen gas under alkaline and neutral pH ranges are highly desirable. Toward the goal, spatially arranged Ni-Co building blocks in metal-organic frameworks (MOF) structures were synthesized on Ni foam by a one-step hydrothermal approach and demonstrated for overall water splitting. Interestingly, the proposed NiCo-MOF/NF shows superior performance for both hydrogen/oxygen evolution reactions (HER/OER) with a small overpotential (vs reversible hydrogen electrode (RHE)) under alkaline/neutral conditions. The NiCo-MOF/NF demonstrates significant HER/OER performance with a small overpotential of 140/270 mV at 10 mA/cm2under alkaline and 252/340 mV at 10 mA/cm2under neutral pH conditions. In addition, NiCo-MOF/NF demonstrates stable overall water splitting performance in a two-electrode configuration with a current density of 20 mA/cm2at the low cell voltage of 1.60 V and excellent stability over 140 h. The improved performance of the electrocatalyst can be associated with the synergistic effect of Ni-Co bimetal clusters in the MOF matrix and the rapid charge transfer kinetics of the catalyst. NiCo-MOF can be an ideal high-performance and stable electrocatalyst for pilot-scale water splitting applications under alkaline and neutral electrolyte conditions.