Synthesis of La–Mg–Ni@Ag composite catalyst and its catalytic performance for borohydride

Abstract

Direct borohydride fuel cells (DBFC) have a promising future as a new type of fuel cell with a high energy conversion rate and a green profile, the performance of which is mainly determined by the anode catalyst. Precious metals as anode catalysts have better catalytic ability but are expensive, limiting their application. Hydrogen storage alloys as anode catalysts can inhibit hydrolysis and enhance the conversion efficiency, but have poor catalytic ability. On this basis, Ag modified La–Mg–Ni hydrogen storage alloy catalyst (La–Mg–Ni@Ag) was synthesized by photo-deposition method in this study. The microstructures and surface morphologies of Ag, La–Mg–Ni alloy and La–Mg–Ni@Ag composite alloy were investigated in detail by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Their catalytic and electrochemical properties towards BH4− were evaluated by cyclic voltammetry (CV) and chronoamperometry (CA). The results show that the La–Mg–Ni@Ag composite catalyst is composed of Ag and La–Mg–Ni alloy phase structure, and La–Mg–Ni alloy particles are closely covered by tiny particles of Ag. In addition, the La–Mg–Ni@Ag composite catalyst has better catalytic activity and stability than those of La–Mg–Ni hydrogen storage alloy catalyst, with an increase in peak oxidation current density of about 50% and an increase in the number of transferred electrons of about 3.