Electrocatalytic oxidation of water (i.e., oxygen evolution reaction, OER) plays crucial roles in energy, environment, and biomedicine. It is a key factor affecting the efficiencies of electrocatalytic reactions conducted in aqueous solution, e.g., electrocatalytic water splitting and glucose oxidation reaction (GOR). However, electrocatalytic OER still suffers from problems like high overpotential, sluggish kinetics, and over-reliance on expensive noble-metal-based catalysts. Herein, 15 nm thick carbon-based shell coated tungsten oxide (CTO) nanospheres are loaded on nickel foam to form CTO/NF. An enhanced electrocatalytic OER is triggered on CTO/NF, with the overpotential at 50 mA cm-2 (317 mV) and the Tafel slope (70 mV dec-1) on CTO/NF lower than those on pure tungsten oxide (360 mV, 117 mV dec-1) and noble-metal-based IrO2 catalysts (328 mV, 96 mV dec-1). A promoted electrocatalytic GOR is also achieved on CTO/NF, with efficiency as high as 189 μA mM-1 cm-2. The carbon-based shell on CTO is flexible for electron transfer between catalyst and reactants and provides catalytically active sites. This improves reactant adsorption and O-H bond dissociation on the catalyst, which are key steps in OER and GOR. The carbon-based shell on CTO retains the catalyst as nanospheres with a higher surface area, which facilitates OER and GOR. It is the multiple roles of the carbon-based shell that increases the electrocatalytic efficiency. These results are helpful for fabricating more efficient noble-metal-free electrocatalysts.
Keywords: carbon-based shell; electrocatalysis; electron transfer; oxidation; tungsten oxide.