Synthesis of vanadium based binary oxides with a yolk–shell structure and their derived electrocatalysts

Abstract

The design and synthesis of non-precious metal composite catalysts with a yolk–shell structure and diverse compositions are challenges in materials science for energy conversion. In this work, we established a facile method to synthesize a series of transition metal oxides with yolk–shell structures (YS structures) by combination of Ostwald ripening and the Kirkendall effect. VO(acac)₂ and other transition metal chlorides were chosen deliberately as the interfusion couple for the development of the YS structure. Among all transition binary metal oxides, WVO_x has a distinct YS structure which can be preserved well in the following sulfurization. The resultant WS₂–V₂O₃ and WS₂–V₃S₄ yolk–shell spheres were certified to be competitive catalyst candidates for the HER and ORR respectively, due to compositional tuning and the YS structures. The fabricated WS₂–V₂O₃ catalyst exhibits excellent HER electrocatalytic activity with a Tafel slope of 87 mV dec⁻¹ and a small overpotential of 89 mV to reach 10 mA cm⁻². The ORR catalyst WS₂–V₃S₄ shows remarkable activity with a positive onset potential of 0.95 V and lower Tafel slope of 51 mV dec⁻¹.