Design of active nickel single-atom decorated MoS₂ as a pH-universal catalyst for hydrogen evolution reaction

MoS₂ has been considered as a potential alternative to Pt-based catalysts in the hydrogen evolution reaction (HER). However, the presence of the inactive in-plane domains limits their intrinsic electrocatalytic activity of the catalyst. Here, we demonstrate a new approach for activating these inactive sites and therefore dramatically enhancing the activity. We discover that decorating single Ni atom on MoS₂ can increase the HER activity in both alkaline and acidic conditions. Experimental and theoretical results indicate that single Ni atom modifiers are inclined to single dispersion in the S-edge sites and H-basal sites of MoS₂, resulting in a favorable change in the adsorption behavior of H atoms on their neighboring S atoms and subsequently the HER activity. Consequently, the single-Ni-atom decorated MoS₂ (Ni_SA-MoS₂) achieved cathodic current density of 10 mA cm⁻² at overpotentials of 98 mV and 110 mV in 1 M KOH and 0.5 M H₂SO₄, respectively. The dispersion of the Ni single atoms in the Ni_SA-MoS₂ is unaffected upon 2000 cycles in both acidic and alkaline conditions. This single atom decorating approach presents a facile and promising pathway for designing active electrocatalysts for energy conversion and storage. © 2018