Antimony Selenide Photocathodes For Highly Efficient Photoelectrochemical Hydrogen Evolution

Energy is the fundamental driven force of the society.With the increase of the global population and the continuous expansion of the economy,the global energy demand is growing dramatically.The excessive consumption of traditional fossil fuels has led to various issues about environmental pollution.Developing clean,no pollution,renewable energy sources become a top priority.Hydrogen generation by photoelectrochemical water splitting using solar energy is an effective way to solve the above-mentioned problems.One of the main challenges of the commercialization of solar hydrogen production techniques is the development of suitable low-cost,high-performance semiconductors for the preparation of photoelectrochemical devices with large areas.Antimony selenide（Sb₂Se₃）,a p-type semiconductor,is a binary single-phase compound withattractive characteristics such as suitable band gap,good carrier diffusion length,and low toxicity,which is considered to be an ideal material for the construction of photocathode.In this thesis,Sb₂Se₃-based photocathodes were prepared and studied for photoelectrochemical hydrogen generation,which mainly contains two parts:In the first part,the photocathode of dendritic Sb₂Se₃/In₂S₃ heterojunction nanorod array thin films covered with low-cost MoS_X catalyst was investigated for PEC water splitting.The composition and morphology of the film were characterized through the scanning electron microscope,high resolution transmission electron microscope and X-ray photoelectron spectroscopy,suggesting that the expected heterojunction-structure photocathode was successfully prepared.The photoelectrochemical performance test showed that the optimized photocathode displayed a high photocurrent density of-27 mA cm^-2 with a half-cell efficiency of 2.6%in the 0.1 M H₂SO₄solution under 1 sun illumination.The kinetic study confirmed that the In₂S₃ layer significantly reduced the carrier bulk transport resistance.Moreover,the charge transfer process on the Sb₂Se₃/In₂S₃ photocathode surface was accelerated significantly,and the charge recombination process was also suppressed efficiently.In the second part,poly-1,1’-diallyl-[4,4’-bipyridine]-1,1’-diium(RV²⁺),an organic molecular film,was introduce the interface of Sb₂Se₃/TiO₂ instead of the traditional inorganic semiconductor as an electron relay..The introduction of RV²⁺layer could significantly improve the photoelectrochemical performance of the Sb₂Se₃-based photocathode.Mechanistic studies indicated that the RV²⁺layer could effectively adjust the energy level between the Sb₂Se₃ and TiO₂ layers.Meanwhile,the RV²⁺layer could effectively inhibit the charge recombination on the surface of Sb₂Se_3,and promote the separation/transfer process during photoelectrochemical hydrogen generation.