Photocathode based on Si containing protective layer of Al2O3 and hydrogen evolution catalyst COP

• Grant number: 20/05476-7
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: August 01, 2020
• End date: July 31, 2021
• Field of knowledge: Physical Sciences and Mathematics - Chemistry - Physical-Chemistry
• Principal Investigator: Lucia Helena Mascaro Sales
• Grantee: João Pedro Gaudencio Ribeiro dos Santos
• Host Institution: Centro de Ciências Exatas e de Tecnologia (CCET). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil
• Associated research grant: 13/07296-2 - CDMF - Center for the Development of Functional Materials, AP.CEPID

Abstract

One of the greatest challenges that humanity has ever faced is the transformation and expansion of the energy matrix using environmentally friendly sources. An excellent alternative is the use of photoelectrochemical systems for decomposing H2O into H2 and O2, which allow the energy storage in chemical bonds. There are many efforts to obtain materials with high incident photon-to-current efficiency to make these systems commercially attractive. Widely used in solar cells, Si exhibits enormous potential and its characteristics of bandgap energy and conduction band level are suitable for the hydrogen production under short overpotential. This overpotential can be easily provided by a solar panel, in a tandem system. However, although Si is a great light absorbent material, its low stability in aqueous electrolytes and slow charge transfer kinetics on the surface are restrictive factors to water splitting reaction. Thus, this project aims to employ two strategies to solve these limitations, (I) formation of protective layers based on Al2O3 and (II) deposition of the hydrogen evolution catalyst based on cobalt phosphide (CoP). It will be evaluated three deposition techniques of the Al2O3 layer on the monocrystalline Si substrate (immersion, electrodeposition and spin coating). The optimization will be performed searching the formation of a thin, adherent and uniform layer. Then, Co will be electrodeposited using pulsed galvanostatic regime in 0.05 mol L-1 Co(NO3)2 + 0.5 mol L-1 KNO3 solution. The conversion of the film from Co to CoP will be carried out by phosphidation. These photocathodes will be characterized by X-ray diffraction, scanning electron microscopy, electrochemical impedance spectroscopy, ultraviolet-visible absorption spectrophotometry and photoelectrochemical measurements using Xenon lamp as a source of illumination and AM 1.0G filter under irradiance of 100 mW cm-2. It is expected that with both methodologies, the material will be obtained with excellent photoelectrochemical performance for application in the hydrogen evolution.