Hollow Core-Shell NiFeS for Enhanced Oxygen Evolution Reaction Electrocatalysis in Water Splitting.

The structural engineering of electrocatalysts plays a pivotal role in accelerating the kinetics of the oxygen evolution reaction (OER) for efficient water splitting. In this work, we report the synthesis of a hollow core-shell structured NiFeS electrocatalyst via a facile hydrothermal-etching-sulfidation strategy. Specifically, spindle-shaped MIL-88A metal-organic frameworks were initially synthesized and subsequently etched with ethanol and nickel nitrate to create a hollow core-shell template, which was then transformed into the HCS-NiFeS catalyst through low-temperature sulfidation. Density functional theory (DFT) calculations identify NiFeS as the primary active species. Benefiting from the abundant active sites and enhanced mass transport provided by the unique core-shell architecture, the resulting catalyst exhibits remarkable OER performance in alkaline media. It achieves a current density of 100 mA cm-2 at a low overpotential of 353 mV, accompanied by excellent long-term stability.