Non-Noble Cobalt Tungstate Catalyst for Effective Electrocatalytic Oxidation of Borohydride.

Abstract

Morphologically tuned cobalt tungstate (CoWO4), a new entrant toward borohydride oxidation reaction (BOR), was explored as it exhibited negligible H2 evolution while enabling rapid BOR. A simple synthetic strategy was employed and fine-tuned to obtain different morphologies of CoWO4 whose urchin-shaped variant gave exciting activity toward BOR. An early and quite negative onset potential of -1.14 V was observed giving a maximum obtainable specific current density of 105.3 mA mg-1. The synthesized variants were investigated in depth by various electrochemical measurements and assessed in light of previous reports toward BOR activity. Hydrodynamic studies were also performed to ascertain the nature of these static electrochemical measurements. Quantitative assessment of the evolved H2, a prominent competitive reaction to BOR, was performed suggesting minimal interference. The probable origin of such morphology-dependent activity was subsequently studied in detail by high-resolution transmission electron microscopy (HR-TEM) analysis, revealing nanometric structures in the urchin-like variant, which enhance the obtainable BOR activity.