Mesoporous Thin-Film NiS<sub>2</sub> as an Idealized Pre-Electrocatalyst for a Hydrogen Evolution Reaction
Cüneyt Karakaya, Navid Solati, Umut Savacı, Emre Keleş, Servet Turan, Serdar Çelebi, Sarp Kaya
Abstract
Developing active, durable, and inexpensive electrocatalysts is critical for hydrogen production to meet ever-growing sustainable energy needs. Nickel sulfides offer significant potential as electrocatalysts for a hydrogen evolution reaction (HER); however, the active phase governing the electrochemical conversion is still under debate. We show that mesoporous thin-film NiS2 synthesized by a novel soft-templating method without post-sulfurization exhibits superior HER activity in alkaline media after a preconditioning step that results in sulfur leaching, amorphization of the surface, and collapse of the mesoporous structure. A comparative analysis with crystalline NiS2 reveals that partial hydroxylation of the under-coordinated Ni sites is responsible for the superior HER activity.