TiS₂ Monolayer as an Emerging Ultrathin Bifunctional Catalyst: Influence of Defects and Functionalization

Abstract

We have envisaged the hydrogen evolution and oxygen evolution reactions (HER and OER) on a two-dimensional (2D) noble-metal-free titanium disulfide (TiS 2 ) monolayer, which belongs to the exciting family of transition metal dichalcogenides (TMDCs). Our theoretical investigation to probe the HER and OER on both the H and T phases of 2D TiS 2 is based on electronic-structure calculations witihin the framework of density functional theory (DFT). Since TiS 2 is the lightest compound among the group-IV TMDCs, it is worth exploring the catalytic activity of a TiS 2 monolayer through the functionalization at the anion (S) site, substituting with P, N, and C dopants as well as by incorporating single sulfur vacancy defects. We have investigated the effect of functionalization and vacancy defects on the structural, electronic, and optical response of a TiS 2 monolayer by determining the density of states, work-function, and optical absorption spectra. We have determined the HER and OER activities for the functionalized and defective TiS 2

Combinatorial Design and Computational Screening of Two-Dimensional Transition Metal Trichalcogenide Monolayers: Toward Efficient Catalysts for Hydrogen Evolution Reaction

“…Although these quantities may be different on the trichalcogenide layers, they are unlikely to be very different given that one is calculating energy differences. Moreover, the same values have been used for Δ G H* on PdS 2 , TiS 2 , and TiO 2 monolayers. ,, …”

“…Moreover, the same values have been used for ΔG H* on PdS 2 , TiS 2 , and TiO 2 monolayers. 15,33,34 Finally, compounds with |ΔG H* | ≤ 0.3 eV are identified as promising catalysts. The choice of the range is based on the volcano plot in Norskov's original work.…”

Substrate Effect on Hydrogen Evolution Reaction in Two-Dimensional Mo2C Monolayers

“…Two-dimensional (2D) materials have emerged as potential HER catalysts owing to their large surface areas and earth-abundant elements. To date, several 2D systems, such as graphene and transition metal dichalcogenides (TMDs), have been studied for HER electrocatalysis [11][12][13][14][15][16] , and the results showed that the HER performance can be improved by intrinsic defects, doping, surface functionalization, strain engineering, phase regulation, and grain boundaries [17][18][19][20][21][22][23][24] . Recently, the 2D transitional-metal carbide/nitride monolayer (MXene) such as Mo2C was experimentally discovered as a new type of 2D material [25][26][27] .…”

Substrate Effect on Hydrogen Evolution Reaction in Two-Dimensional Mo2C Monolayers

“…and the results showed that the HER performance can be improved by intrinsic defects, doping, surface functionalization, strain engineering, phase regulation, and grain boundaries [17][18][19][20][21][22][23][24].…”