Study on bubble dynamic characteristics and mass transfer mechanism in photoelectrochemical water splitting for hydrogen production
The long-term continuous growth of bubbles on the surface of the photoelectrode is an important factor affecting the efficiency of photoelectrochemical water splitting for hydrogen production.The effects of laser power and pressure in the cell on the evolution characteristics of bubbles and the mass transfer process at the gas-liquid interface were systematically studied by a multi-parameter simultaneous in-situ measurement and analysis method of photochemistry and bubble dynamics.The results demonstrate that bubbles under different laser powers and pressures follow similar growth rules before detachment.The gas mass yield reaches an extreme value at 80 kPa,indicating that appropriately lowering the pressure is beneficial to gas production.In addition,as the pressure decreases,the bubble detachment diameter increases and period shortens.By comparing force balance models considering different Marangoni forces,it is found that the force balance model considering both concentration Marangoni force and thermal Marangoni force has a prediction error of less than 5％for bubble detachment diameter and the concentration Marangoni force is the main factor affecting bubble detachment diameter under different pressures.Through solving the mass transfer coefficients,it can be found that the gas-liquid mass transfer is dominated by single-phase free microconvection under different pressure conditions in low photocurrent densities,but the effect of bubble-induced microconvection induced by expansion of gas-liquid interface on mass transfer is enhanced with the increase of photocurrent density.
photoelectrochemical water splittingbubblehydrogen productionpressuremass transfer
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