First-principles study of the atomic structures and catalytic properties of monolayer TaS2 with intrinsic defects

Abstract

Monolayer tantalum disulfide (TaS2) has attracted much attention for its superconducting and charge-density-wave (CDW) properties. However, multiple structural defects are frequently observed in fabricated samples and greatly influence their performance. Using first-principles calculations, we systematically investigate the atomic structures, energetic stability, and electronic and catalytic properties of six common point defects and six grain boundaries (GBs) of the monolayer TaS2. The single S atom vacancy defect of the monolayer TaS2 has the lowest formation energy below 2 eV, regardless of the chemical environment. For GBs, 4|4 and 4|8 defect rings without homoelemental bonds are predicted to form more easily than the 5|7 defect ring. For the hydrogen evolution reaction (HER) process, the binding strengths of different defect sites are related to the p- or d-band center of the S or Ta atom, respectively. In particular, TaS2 with a single S vacancy defect shows superior catalytic activity with a H atom adsorption energy of 0.1 eV and a Tafel barrier of 0.25 eV. These theoretical results provide vital guidance for detecting various defects of two-dimensional TaS2 in experiments and modulating catalytic properties via defect engineering.