Modification Of Silicon Photocathode By Nano-catalyst And Nanostructure For Efficient Water Splitting

Converting solar energy to electricity or chemical energy is one of the important approaches to overcome the limited supply of clean energy source. The key issue of the solar conversion is to search for the appropriate solar conversion material and build an efficient conversion system. Silicon, as a common semiconductor material, is a promising material for the photocathode in a PEC cell, since its ideal band structure, excellent charge carrier transport properties, and low cost. However, the sluggish surface reaction, high reflectivity and carrier recombination rate are major drawbacks for silicon. This restricts its further development as PEC photocathode. Accordingly, modification of the silicon photocathode is particularly important. This article mainly carried out the surface modification by loading N-doped CNDs catalysts and the etched nano-pyramid structure to improve the performance of silicon photocathode. The main research work is divided into the following two parts:（1） In recent years, CNDs have aroused great interesting, due to their stable, non-toxic,low cost and other novel photophysical performance. In this article, we firstly electrodeposited CNDs into np⁺-Si photocathode’s surface using the CND solution prepared by electrochemical method. By changing the deposition time, we can optimize the PEC performancee of CNDs/np⁺-Si photocathode. Then we perform N₂ plasma treatment to further enhance its PEC performance. The effect Pt catalyst is then studied. TEM, SEM,XPS and Raman were carried out to study the N-CNDs/np⁺-Si photocathode’s surface structure and composition and we explained the mechanism for the PEC performance enhancement.（2） Various morphologies of nanostructured materials can enhance light absorptionand carrier mobility or collection. They demonstrated unique advantages. However, when the conventional catalysts such as Pt were deposited on the Si nanowire structures, it can not be distributed in the surface of the nanowires uniformly, but only on the top of the nanowires. Here, we prepared nanoporous silicon and the black nano-pyramid silicon by metal-catalyzed chemical etching（MCCE） to overcome this shortcoming. We found that silicon nanoporous structure, compared to the nano-pyramid one, its PEC performance is more excellent. However, after deposition of Pt nanoparticles, the PEC properties of pyramid-Si are superior to nanoporous-Si. Although the open-circuit voltage and short-circuit photocurrent has a very significant incresment, the stability of the electrode is not very good. Therefore a surface protection layer is necessary for increasing the stability of the electrode. This will be our further work.