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

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.