Enhancing catalytic properties of noble metal@MoS2/WS2 heterojunction for the hydrogen evolution reaction

Abstract

Transition metal disulfides (MoS2 and WS2) are regarded as the potential candidates for efficient hydrogen evolution reaction. However, their practical application is hindered due to the inert basic plane, the few active sites and the low electrical conductivity. The specially coupled interface with strong electronic interaction and low interface impedance in heterostructure helps to improve the catalytic hydrogen evolution performance of the catalyst. Therefore, we construct MoS2/WS2 heterojunction to investigate it's catalytic hydrogen evolution behavior. The transition metal elements (Pt and Pd) are doped for further enhancing the catalytic hydrogen evolution performance of the heterojunction. Our results show that the Pt-doped heterojunction (Pt@MoS2/Pt@WS2) has a ΔGH of 0.008 eV as well as Volmer/Heyrovsky reaction energy barrier of 0.293 eV/0.702 eV, which can be used as a high-efficiency hydrogen evolution catalyst.Naturally, the high catalytic activity of Pt@MoS2/Pt@WS2 is attributed to four important factors. Firstly, the unique heterostructure improves the inherent electrical conductivity and catalytic activity. Secondly, the doped elements narrow the band gap, which further promotes the electron transport of the catalyst. Thirdly, the new impurity levels produced by doping make the catalysts easy to bond hydrogen protons. Fourthly, the unique charge distribution of electron depletion-accumulation-depletion regions on the basic plane invites the competitive effect between adsorption enhancement and adsorption weakening, thereby inducing the best Gibbs free energy change of adsorbed hydrogen and the low hydrogen evolution reaction energy barrier.