Nickel-Doped Silver Sulfide: An Efficient Air-Stable Electrocatalyst for Hydrogen Evolution from Neutral Water

A low-cost, platinum-free electrocatalyst for hydrogen (H 2 ) generation via the water splitting reaction holds great promise to meet the demand of clean and sustainable energy sources. Recent studies are mainly concerned with semiconducting materials like sulfides, selenides, and phosphides of different transition metals as electrocatalysts. Doping of the transition metals within the host matrix is a good strategy to improve the electrocatalytic activity of the host material. However, this activity largely depends on the nature of the dopant metal and its host matrix as well. To exploit this idea, here, in the present work, we have synthesized semiconducting Ag 2 S nanoparticles and successfully doped them with different transition metals like Mn, Fe, Co, and Ni to study their electrocatalytic activity for the hydrogen evolution reaction from neutral water (pH = 7). Among the systems doped with these transition metals, the Ni-doped Ag 2 S (Ni-Ag 2 S) system shows a very low overpotential (50 mV) with high catalytic current in neutral water. The trend in electrocatalytic activity of different transition metals has also been explained. The Ni-Ag 2 S system also shows very good stability in ambient atmosphere over a long period of time and suffers no catalytic degradation in the presence of oxygen. Structural characterizations are carried out using X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy to establish the phase purity and morphology of the materials.