Doping phosphorus into hollow Co3O4 microspheres as a bifunctional catalyst for water splitting process

Abstract

The energy demand of the world is increasing rapidly while the remaining fossil fuels is running out. Hydrogen is considered as a potential replacement of energy source as it is clean and numerous. Water electrolysis is one of the method to extract hydrogen gas and oxygen gas from water. To speed up the reaction and lower the reaction energy, catalyst acts as an important role in the water-splitting process. Water-splitting consists of two reactions, which are hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Hollow cobalt (II, III) oxide (Co3O4) is a strong catalyst for producing oxygen but is very weak at producing hydrogen. It was found that filling phosphorus into the oxygen vacancies of the Co3O4 nanosheet can improve the efficiency of both HER and OER. In this project, hollow phosphorus-doped cobalt (II, III) oxide microspheres (P-Co3O4) as a bifunctional catalyst for water splitting was studied. The hollow Co3O4 microspheres were prepared by reacting the cobalt (II) nitrate and citric acid during the solvothermal process, followed by calcination of 400oC for 2 hours. The hollow P-Co3O4 microspheres were prepared by doping the phosphorus into the hollow Co3O4 microspheres in the argon atmosphere at 400 oC for 2 hours. For materials characterization, scanning electron microscope (SEM) was used to provide the morphology and compositional information was examined by energy dispersive X-ray spectroscopy (EDS) mapping. X-ray diffraction (XRD) was also used to investigate the crystallography of the materials.