电解液浓度对光电极表面气泡演化及传质特性的影响  

Effect of electrolyte concentration on bubble evolution and mass transfer characteristics on surface of photoelectrode

作　　者：王孟莎 徐强[1] 聂腾飞 罗欣怡 郭烈锦[1] Wang Meng-Sha;Xu Qiang;Nie Teng-Fei;Luo Xin-Yi;Guo Lie-Jin(State Key Laboratory of Multiphase Flow in Power Engineering,Xi’an Jiaotong University,Xi’an 710049,China)

机构地区：[1]西安交通大学,动力工程多相流国家重点实验室,西安710049

出　　处：《物理学报》2024年第18期268-277,共10页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:52076175)资助的课题。

摘　　要：在光电化学分解水反应中,气泡会覆盖光电极表面的反应区域,从而影响反应阻抗和气液传质.本文搭建了激光照射系统,并将其与电化学工作站、高速显微成像系统耦合.在不同电解液浓度下(Na_(2)SO_(4),0.1—2.0 mol/L),研究了TiO_(2)析气光电极表面单个氧气泡的演化行为及其传质特性.随着电解液浓度从0.1 mol/L升高到2.0 mol/L,溶液电阻与气泡附加电阻降低,气泡稳定生长阶段的过电势从0.113 V下降到-0.089 V.气泡在成核、生长和脱离阶段会引起过电势的波动,这与液相中溶解气浓度的变化引起的阻抗变化相吻合.通过分析析气效率与气泡覆盖率的关联,发现电解液浓度提高会导致气泡覆盖率和析气效率同步下降.通过计算舍伍德无量纲数,发现总对流传质系数随着电解液浓度的增大而增大;单相自然对流在气体产物传递过程中占据主导地位,其传质系数比气泡诱导对流传质系数大一个数量级.In the photoelectrochemical water splitting reaction system,bubbles will cover the reaction area on the photoelectrode surface,affecting the reaction impedance and gas-liquid mass transfer.A laser irradiation system is built and it is coupled with an electrochemical workstation and high-speed microscopic imaging system.The evolution behavior and mass transfer characteristics of single O_(2)bubble on the TiO_(2)photoelectrode are studied at different electrolyte concentrations(Na_(2)SO_(4),0.1-2.0 mol/L).With the increase of electrolyte concentration from 0.1 mol/L to 2.0 mol/L,the solution resistance and bubble additional resistance decrease,and the overpotential in the stable growth stage of bubble decreases from 0.113 V to-0.089 V.The bubble will cause the fluctuation of overpotential in the nucleation,growth and detachment stages,which is consistent with the impedance change caused by the change of dissolved oxygen concentration in the liquid phase.By analyzing the correlation between gas evolution efficiency and bubble coverage,it is found that the increase of electrolyte concentration will lead the bubble coverage and gas evolution efficiency to decrease simultaneously.By calculating the Sherwood dimensionless number,the results show that the total convective mass transfer coefficient increases with the electrolyte concentration increasing.Single-phase natural convection plays a dominant role in the process of gas product transfer,and its mass transfer coefficient is one order of magnitude larger than that of bubble-induced convection.In summary,by adjusting the electrolyte concentration,the bubble on the gas evolution photoelectrode surface can be effectively removed and the mass transfer of the system can be optimized,which is of great significance in improving the efficiency of photoelectrochemical water splitting.

关 键 词：光电化学 气泡动力学 浓度 气液传质 

分 类 号：O646[理学—物理化学]