A mechanism in boosting H2 generation: nanotip-enhanced local temperature and electric field with the boundary layer.

ABSTRACT

The sluggish kinetics of oxygen evolution reaction (OER) is the bottleneck of water splitting. Hence, we designed a nanowire Co3O4@nickel foam (Co3O4-NW@NF) electrode to boost OER utilizing the locally enhanced interfacial Joule heating and electric field within the diffusion layer. Results show that the morphology of Co3O4@NF could be regulated in nanowires, nanosheets, and nanoclusters by controlling the doping amount of fluoride ions (F-). F- served as a complexing agent to regulate the rate of crystal nucleus, and then morphologies could be tuned. compared to others, nanowire structures have a much lower potential (298 mV vs. RHE, 10 mA cm-2) and Tafel slope (48.11 mV dec-1). This better electrochemical performance was confirmed by the Density Functional Theory (DFT) that the (311) facet with oxygen vacancies of Co3O4 has a low onset potential (0.36 V) for the kinetic rate of OER. A much better mass transfer by the nanowire-enhanced interfacial Joule heating and electric field within the diffusion layer also accounted for superior OER activity, confirmed by COMSOL simulation. In a word, the design of the nanotip structure offers a novel way to boost the OER rate by enhancing electron transfer and mass transport simultaneously.