Defect engineering in two-dimensional Janus pentagonal noble metal sulfide MXY (M=Pd, Pt; X, YS, Se, Te; X≠Y) materials for highly efficient electrocatalytic hydrogen evolution reaction

The rational design of an electrocatalyst with excellent catalytic activity and high stability is at the core of large-scale hydrogen production from water splitting. As a fascinating, innovative class of effective electrocatalysts for hydrogen evolution reaction (HER), two-dimensional (2D) pentagonal noble metal sulfide MX2 (M = Pd, Pt; X = S, Se, Te) have emerged as promising materials, but they are still suffering from the intrinsic activity for practical applications. The catalytic performance of the catalyst was adjusted by optimizing the electronic configuration of the catalyst and introducing Janus asymmetry and defect engineering. Here, we successful designed and demonstrated 2D defect Janus pentagonal noble metal sulfide materials (defect penta-MXY; M = Pd, Pt; X,YS, Se, Te (X≠Y)). The results show that the catalytic performance was significantly improved after the introduction of defects and Janus, with the best hydrogen adsorption Gibbs free energy (from |ΔGH*|>1eV of penta-MX2 to |ΔGH*|<0.2 eV of defect penta-MXY), and has excellent exchange current density (−16.96 A cm2). Interestingly, among the six catalysts, penta-PtSSe-VSe, penta-PdSSe-VSe, penta-PtSTe-VTe and penta-PtSeTe-VTe have higher work functions (∼5.52 eV), which promote the Volmer reaction step of HER at lower overpotentials (The energy barrier of penta-PtSSe-VSe1 is only 1.01 eV). Moreover, we further revealed that the penta-MXY-VY1 materials exhibit excellent thermal and electrochemical stability, and the reasons for the improvement of electrocatalytic activity were investigated by studying the charge density difference, Bader charges, crystal orbital Hamilton population and d-band center (The penta-PtSSe-VSe1 is −0.15 eV). The procedure followed in this work may be extended to the Janus pentagonal materials, thus expanding their potential application fields.