The Electrochemical Properties Research Of Catalysts Based On Rh₁₇S₁₅ And Their Application For Hydrochloric Acid Electrolysis

The chlorine with high value can be produced by electrolyzing hydrochloric acid which is byproduct of chemical industry. In order to reduce the cost of the electrolysis, gas diffusion electrode was applied in the hydrochloric acid electrolysis, and the electrolytic voltage can be reduced by about IV. However the traditional noble metal such as platinum catalyst is easily catalyst poisoned and dissolved in hydrochloric acid electrolysis, because the environment is highly complex and corrosive, so the noble metal can not be considered for hydrochloric acid electrolysis application. Recently the RhxSy is chosen as catalyst for hydrochloric acid electrolysis due to its excellent stability in hydrochloric acid. However the RhxSy has shortcomings of low catalytic activity.As regards the activity, RhxSy is a mixture of different crystalline phases with different valences and stoichiometry, in which it at least comprises the species Rj2S3, Rh17Sis, Rh3S4and some amount of metallic rhodium. Of all these species Rh17S15is the most active, while the remaining species present little or no activity. In order to improve the catalytic activity of RhxSy catalyst, a lot of research was did based on Rh17S15, in which the Rh17S15/C catalyst、 Rh-Rh17S15/C catalyst and Rh17S15/CNT catalyst were synthesised from RhCl3by a facile method using sulphur source and reducing agent, followed by an additional thermal treatment at650℃in helium. By XRD characterization, the constituent ratio of Rh17S15to Rh in the electrocatalysts, ranging from51～100%, varied with the increase of amount of (NH4)2S2O3or NaBH4. The catalysts were studied in terms of morphological characteristics and ORR activity. Morphologies of the resulting catalysts were characterized by scanning electron microscopy and transmission electron microscopy. Nanoparticles were found to be highly dispersed on the carrier material. Activity of the prepared catalysts were addressed using a series of cyclic voltammetry and rotating disk experiments in1M HCl electrolyte, in which the100%of Rh17S15in the electroactalysts were found to be the most stable in1M HCl electrolyte. The sulfided catalyst with a82.17%of Rh17S15showed the better performance for the ORR.Then the gas diffusion electrode with Rh17S15/C was prepared. The prepared electrode was tested in the simulated operating condition, the electrode was stable operation during56h’s test and cell shutdown test.