Substrate-mediated growth of vanadium carbide with controllable structure as high performance electrocatalysts for dye-sensitized solar cells

Abstract

Transition metal carbides (TMCs) are promising alternatives to noble-metal based catalysts in many fields. Controlling the morphology of TMCs is an effective approach to promote the catalytic performance. We here report a substrate-mediated method to direct the growth of vanadium carbide (VC) using graphene oxide as the nucleation and growth substrate. By carefully choosing the synthesis conditions, we can tune the structure of VC nanoparticles from cuboctahedron (VC-ch) to cubic (VC-cb). The obtained hybrid of VC-ch on graphene sheets (VC-ch/GS) shows excellent catalytic activity towards the triiodide reduction reaction in terms of the charge transfer resistance (R_ct = 0.27 Ω cm²), outperforming its counterpart VC-cb/GS (R_ct = 1.69 Ω cm²). The energy conversion efficiency of the Dye-Sensitized Solar Cells (DSSC) with the VC-ch counter electrode (CE) reached 7.92%, comparable to a Pt based CE of 7.79%. Experimental combined with theoretical calculation results suggest that the high catalytic activity of VC-ch may originate from the special atom packing state of the VC(111) facet.