Bubble transport characteristic on hydrogen evolution reaction of aligned porous electrode

Bubble management in electrocatalysis is very important for reducing overpotential of hydrogen evolution reaction. In this paper, a pore structure model of an aligned porous electrode is established, and the effect of pore size and pore length on bubble transport is studied using the phase field method. The entire transport process of the bubble can be divided into two stages: the motion of bubbles inside pores and the detachment from the pores. The results show that increasing pore size can significantly increase the velocity of the bubble within the pore. Regarding the detachment process of bubble from pores, the movement velocity of the bubble is accelerated due to the different Laplace pressure of the bubble in the inner and outer parts of the pore. However, the pressure gradient decreases with an increase in pore size, resulting in weakened acceleration effect. These two effects are contradictory, and the final effect of the pore size on the bubble transport is related to the pore length. The shorter pore length and smaller pore size strengthen the promotion of the detachment process to bubble transport. In addition, the simulation results provide explanations for electrochemical measurements and bubble visualizations.