Investigations on the kinetics properties of the electrochemical reactions of MlNi_(3.55)Co_(0.75) - xMn_(0.4)Al_(0.3)(Cu_(0.75)P_(0.25))_x (x = 0.0, 0.1, 0.2, 0.3, 0.4) hydrogen storage alloys

摘要

The effect of the multiple substitution of Cu-P for Co on the kinetics properties of the novel hydrogen storage alloys MlNi_(3.55)Co_(0.75) - xMn_(0.4)Al_(0.3)(Cu_(0.75)P_(0.25))_x (x-0.0, 0.1, 0.2, 0.3, 0.4) was investigated. The electrochemical impedance spectroscopy (EIS) method was applied to characterize the kinetics properties of the electrochemical reactions of the series composite alloys. It was found that the charge-transfer reaction resistance R_(ct) decreased from 122.2 to 106 mΩg and the exchange current density I_0 increased from 210.1 to 242.2 mA g~(-1) with increasing Cu-P content. Moreover, the hydrogen transfer resistance R_a remarkably decreased from 149.1 to 17.23 mf! g, and the hydrogen diffusion coefficient D increased from 1.01 x 10~(-11) to 7.01 x 10~(-11) cm~2 s~(-1) with the increase of x from 0.0 to 0.4. The measurements revealed that the overall kinetics properties of the electrochemical reactions were improved as the multiple substitution, especially for the sample x = 0.4.