Yang Weikang, Gu Dongxu, Liu Xin, Luo Qiangmin
School of Chemistry and Chemical Engineering, Chongqing University Chongqing 400044 PR China
Institute of Intelligent Innovation, Henan Academy of Sciences Zhengzhou Henan 451162 P. R. China.
RSC Adv. 2025 May 21;15(21):17015-17022. doi: 10.1039/d5ra02159f. eCollection 2025 May 15.
The coverage of hydrogen bubbles decreases the active area of electrodes, resulting in reduced electrochemical performance. However, bubble growth locally decreases hydrogen concentration, thereby mitigating concentration overpotential. This dual effect highlights the significance of investigating the effect of bubbles on hydrogen removal in electrode design. Since hydrogen removal primarily occurs molecular transport across bubble interfaces (which drives bubble growth), we analyzed the multi-bubble growth kinetics ( = ) on Ni electrodes with varying roughness to compare the hydrogen removal effect at the bubble interface. For a low-roughness (LR-surface) electrode, bubble growth follows conventional time coefficients () close to 0.5, indicating that the bubbles were in an H-saturated environment, where the entire bubble interface participated in hydrogen removal. The elevated bubble density on a medium-roughness (MR-surface) electrode provides additional bubble interfaces for hydrogen removal, reducing hydrogen concentration ( decrease from 93.91 to 63.11). The time coefficient of bubble growth remained at 0.5, confirming that the increased bubble interface was also in the hydrogen-saturated condition. In contrast, on a high-roughness (HR-surface) electrode, the competition of excessive coexisting bubbles for hydrogen molecules leads to the narrowing of the H-saturated region, and the top of the bubble is in the H-unsaturated region, indicating that not all of the additional bubble interface is involved in the hydrogen removal, which is manifested as the decrease in the time coefficient ( decrease from 0.5 to 0.42). Based on the experimental results, we conclude that the hydrogen removal effect does not increase linearly with increasing numbers of coexisting bubbles on the electrode. The transition in bubble growth kinetics reflects the varying degree of bubble interface involvement in hydrogen removal, which may serve as a consideration for designing the density of bubble nucleation sites on electrodes.
氢气泡的覆盖会减小电极的活性面积，导致电化学性能下降。然而，气泡的局部生长会降低氢浓度，从而减轻浓差过电位。这种双重效应凸显了在电极设计中研究气泡对氢去除影响的重要性。由于氢的去除主要发生在分子通过气泡界面的传输过程中（这驱动了气泡的生长），我们分析了不同粗糙度的镍电极上的多气泡生长动力学（= ），以比较气泡界面处的氢去除效果。对于低粗糙度（LR表面）电极，气泡生长遵循接近0.5的传统时间系数（），这表明气泡处于氢饱和环境中，整个气泡界面都参与了氢的去除。中等粗糙度（MR表面）电极上增加的气泡密度为氢的去除提供了额外的气泡界面，降低了氢浓度（从93.91降至63.11）。气泡生长的时间系数保持在0.5，这证实增加的气泡界面也处于氢饱和状态。相比之下，在高粗糙度（HR表面）电极上，过多共存气泡对氢分子的竞争导致氢饱和区域变窄，气泡顶部处于氢不饱和区域，这表明并非所有额外的气泡界面都参与了氢的去除，这表现为时间系数的下降（从0.5降至0.42）。基于实验结果，我们得出结论，电极上共存气泡数量增加时，氢去除效果并非线性增加。气泡生长动力学的转变反映了气泡界面参与氢去除的不同程度，这可作为设计电极上气泡成核位点密度时的一个考虑因素。
