Cr-added nickel sulfides as electrocatalysts for oxygen evolution reaction

Ni0.5-xCrxS compounds (x = 0, 0.02, 0.33) as electrocatalysts for oxygen evolution reaction (OER) were synthesized by a microwave-assisted route that provided an increased surface area. It was found that the OER performance of the NiS electrocatalyst was enhanced by chromium addition. Chromium incorporation was evidenced with Rietveld refinement and XPS analysis. Peak position shifts in the XPS spectra and increases in the lattice parameters a and c indicated the Cr incorporation into the NiS structure. Enhanced kinetic properties, stability and OER activities were achieved with chromium addition due to its contribution to the electronic structure. All samples exhibited competitive results with similar studies and demonstrated better OER activities than the benchmark RuO2. Among three samples, 2 at.% Cr containing NiS sample exhibited the lowest overpotential (334 mV), Tafel slope (42 mV dec−1) and charge transfer resistance (6.1 Ω) values leading to an enhanced OER performance.