Self‐Optimization of the Active Site of Molybdenum Disulfide by an Irreversible Phase Transition during Photocatalytic Hydrogen Evolution

Abstract

The metallic 1T-MoS has attracted considerable attention as an effective catalyst for hydrogen evolution reactions (HERs). However, the fundamental mechanism about the catalytic activity of 1T-MoS and the associated phase evolution remain elusive and controversial. Herein, we prepared the most stable 1T-MoS by hydrothermal exfoliation of MoS nanosheets vertically rooted into rigid one-dimensional TiO nanofibers. The 1T-MoS can keep highly stable over one year, presenting an ideal model system for investigating the HER catalytic activities as a function of the phase evolution. Both experimental studies and theoretical calculations suggest that 1T phase can be irreversibly transformed into a more active 1T' phase as true active sites in photocatalytic HERs, resulting in a "catalytic site self-optimization". Hydrogen atom adsorption is the major driving force for this phase transition.

Strong Charge Transfer at 2H–1T Phase Boundary of MoS2 for Superb High‐Performance Energy Storage

“…Moreover, the intensity ratios between the 2S and Mo sites shown in Figure c and Figure d were found to be <0.3 and 0.6–0.7, respectively. These results are in reasonable agreement with previous reports and clearly suggest the coexistence of 1T and 2H phases within the individual MoS 2 sheet …”

Defect Engineering of MoS2 and Its Impacts on Electrocatalytic and Photocatalytic Behavior in Hydrogen Evolution Reactions

“…These decreases of molar ratio support the fact that S‐vacancies are introduced during hydrogen reduction process. Among these samples, Ru/MoS 2− x (200) shows the lowest Mo:S ratio of 1: 1.42, which means S‐vacancies and 1T‐phase in this sample reached a higher concentration, which play important roles in catalytic reactions as will be discussed later . Besides, Mo:S ratio of MoS 2− x samples (without Ru) was determined to be 1:1.75 for MoS 2− x (150), 1:1.64 for MoS 2− x (200) and 1:1.70 for MoS 2− x (250), further confirming the formation of vacancies upon this process, and the existed Ru benefits to S‐vacancies formation at lower temperature, but is likely to repair defects at higher temperature reduction.…”

Metallic MoS2 for High Performance Energy Storage and Energy Conversion

“…The authors related the enhancement in the 2H MoS 2 case to its smaller particle size, which can be easily adsorbed to the CdS surface, providing a better contact for the transport of the photoexcited electrons. Wang et al prepared highly stable metallic 1T MoS 2 that is vertically rooted over TiO 2 nanofiber. After investigating their photocatalytic activity before and after exfoliation, the exfoliated TiO 2 @MoS 2 showed a superlinear increase over time, giving a better photocatalytic performance.…”