Highly Stable Molybdenum Disulfide Protected Silicon Photocathodes for Photoelectrochemical Water Splitting

Abstract

Developing materials, interfaces, and devices with improved stability remains one of the key challenges in the field of photoelectrochemical water splitting. As a barrier to corrosion, molybdenum disulfide is a particularly attractive protection layer for photocathodes due to its inherent stability in acid, the low permeability of its basal planes, and the excellent hydrogen evolution reaction (HER) activity the MoS edge. Here, we demonstrate a stable silicon photocathode containing a protecting layer consisting of molybdenum disulfide, molybdenum silicide, and silicon oxide which operates continuously for two months. We make comparisons between this system and another molybdenum sulfide-silicon photocathode embodiment, taking both systems to catastrophic failure during photoelectrochemical stability measurements and exploring mechanisms of degradation. X-ray photoelectron spectroscopy and transmission electron microscopy provide key insights into the origins of stability.

Layer dependence of the photoelectrochemical performance of a WSe2 photocathode characterized using in situ microscale measurements

“…12) and Fe 2 O 3 . 13,14 Previously explored photocathode materials include silicon, 15 InGaP 16 and Cu 2 O. 17 Unfortunately, the large bandgap or unsuitable band-edge position seriously limits the water-splitting efficiency of PECs fabricated using these materials.…”

Ion Beam Defect Engineering on ReS2/Si Photocathode with Significantly Enhanced Hydrogen Evolution Reaction

“…Generally, the TMDs/Si composite photoelectrodes have advantages of large specific surface areas, low material costs, and highly catalytic activities. Besides, the TMDs/Si configuration can effectively alleviate the poor kinetics for absorbing hydrogen ions (H + ) and photocorrosions on surface of p‐Si . Furthermore, the HER efficiency and stability in a solar‐driven PEC water splitting can be efficiently improved .…”

Durability Testing of Photoelectrochemical Hydrogen Production under Day/Night Light Cycled Conditions

“…Maier et al demonstrated relatively low, but stable photocurrent under the HER conditions for 60 days in 1 M HCl using a Pt-coated crystalline silicon (c-Si), [8] while a recent study by the Jaramillo group used a thin MoS 2 protected c-Si to show durability for up to 62 days. [9] While these longterm tests demonstrate steady-state operational stability of these devices, practical devices will be subjected to daily day/ night cycling, which will vary the potential at the semiconductor/protection layer/catalyst-electrolyte interface. Thus, there is a need to understand how this cycling will affect stability.…”