Electrochemical performance of AB2 metal hydride alloys measured at −40°C

Abstract

The low-temperature (−40 °C) electrochemical performance of Y-, Si-, Fe-, Cu-, and Mo-partially substituted AB2 metal hydride alloys was studied. The surface area and catalytic ability of these alloys were obtained from the double-layer capacitance and the product of the double-layer capacitance and charge-transfer resistance from AC impedance measurement, respectively. With the increase in amount of substitution, the surface areas in these substituted alloys showed different degrees of increase: Y-addition exhibited the largest increase, followed by Si-addition, and then Cu-, Mo-, and Fe-additions. The surface catalytic abilities of Si-containing alloys were the highest and followed by those of Mo-containing alloys. Cu-, Y-, and Fe-additions reduced the surface catalytic ability. The resistance at −40 °C benefited from the incorporations of Si, Mo, and Y, and deteriorated with the incorporations of Cu and Fe. In the best scenario of a single element-substituted AB2 alloy, the resistance at −40 °C is still higher than that from a commercially available AB5 alloy. Since the contributions to the low temperature performance of AB2 alloys from various modifiers are not the same, the combination of several modifiers is possible for further optimization.