Molybdenum Tungsten Disulfide with a Large Number of Sulfur Vacancies and Electronic Unoccupied States on Silicon Micropillars for Solar Hydrogen Evolution
Journal
ACS Applied Materials and Interfaces
Journal Volume
12
Journal Issue
49
Pages
54671-54682
Date Issued
2020
Author(s)
Abstract
Hydrogen energy is a promising alternative for fossil fuels because of its high energy density and carbon-free emission. Si is an ideal light absorber used in solar water splitting to produce H2 gas because of its small band gap, appropriate conduction band position, and high theoretical photocurrent. However, the overpotential required to drive the photoelectrochemical (PEC) hydrogen evolution reaction (HER) on bare Si electrodes is severely high owing to its sluggish kinetics. Herein, a molybdenum tungsten disulfide (MoS2-WS2) composite decorated on a Si photoabsorber is used as a cocatalyst to accelerate HER kinetics and enhance PEC performance. This MoS2-WS2 hybrid showed superior catalytic activity compared with pristine MoS2 or WS2. The optimal MoS2-WS2/Si electrode delivered a photocurrent of -25.9 mA/cm2 at 0 V (vs reversible hydrogen electrode). X-ray absorption spectroscopy demonstrated that MoS2-WS2 possessed a high hole concentration of unoccupied electronic states in the MoS2 component, which could promote to accept large amounts of carriers from the Si photoabsorber. Moreover, a large number of sulfur vacancies are generated in the MoS2 constituent of this hybrid cocatalyst. These sulfur defects served as HER active sites to boost the catalytic efficiency. Besides, the TiO2-protective MoS2-WS2/Si photocathode maintained a current density of -15.0 mA/cm2 after 16 h of the photocatalytic stability measurement. ? 2020 American Chemical Society.
Subjects
Catalyst activity; Electrodes; Energy gap; Fossil fuels; Hydrogen fuels; Layered semiconductors; Molybdenum compounds; Oxide minerals; Photocurrents; Photoelectrochemical cells; Reaction kinetics; Silicon compounds; Solar absorbers; Sulfur; Sulfur compounds; Titanium dioxide; Tungsten compounds; X ray absorption spectroscopy; Catalytic efficiencies; High energy densities; Photoelectrochemicals; Reversible hydrogen electrodes; Solar water splitting; Stability measurements; Tungsten disulfide; Unoccupied electronic state; Silicon
Other Subjects
Catalyst activity; Electrodes; Energy gap; Fossil fuels; Hydrogen fuels; Layered semiconductors; Molybdenum compounds; Oxide minerals; Photocurrents; Photoelectrochemical cells; Reaction kinetics; Silicon compounds; Solar absorbers; Sulfur; Sulfur compounds; Titanium dioxide; Tungsten compounds; X ray absorption spectroscopy; Catalytic efficiencies; High energy densities; Photoelectrochemicals; Reversible hydrogen electrodes; Solar water splitting; Stability measurements; Tungsten disulfide; Unoccupied electronic state; Silicon
Type
journal article