Mass transfer mechanism during bubble evolution on the surface of photoelectrode

Influence of subatmospheric pressure on bubble evolution on the TiO2photoelectrode surface

“…where z is the stoichiometric number and it is taken as z = 4 in this paper, f G is the gas evolution efficiency and f G = 1 À (1 À y c ) 2.5 , y c is the rate of bubble coverage and y c = R 0 contact =R 0 laser , and R 0 contact is the contact radius. k e is the mass transfer coefficient of dissolved oxygen in the liquid phase, whose unit is m s À1 , which is related to the micro-convection term k b caused by bubbles and the single-phase mass transfer term k s caused by the concentration difference, 49,67,69…”

“…Δ C can be estimated from the interface supersaturation model proposed by H. Vogt, 53,65–68 where z is the stoichiometric number and it is taken as z = 4 in this paper, f G is the gas evolution efficiency and f G = 1 − (1 − θ c ) 2.5 , θ c is the rate of bubble coverage and θ c = , and is the contact radius. k e is the mass transfer coefficient of dissolved oxygen in the liquid phase, whose unit is m s −1 , which is related to the micro-convection term k b caused by bubbles and the single-phase mass transfer term k s caused by the concentration difference, 49,67,69 where D is the diffusion coefficient of dissolved oxygen in the electrolyte, whose unit is m 2 s −1 , and D = 2.01 × 10 −9 m 2 s −1 in this paper. d b is the bubble diameter, whose unit is m. Re is the Reynolds number and Sc is the Schmidt number.…”

In Situ Investigation of Oxygen Bubble Evolution at Photoanode Surface Affected by Reaction Temperature

“…Re is the Reynolds number, the flow velocity u is calculated from the expansion and contraction of bubble contact lines. Θ is the bubble coverage a 0 = ( 13 + 71 1 − 2 3 f normalg ) × 10 − 6 …”

“…Θ is the bubble coverage. 64 Sc is the Schmidt number; a 0 is the expansion coefficient of the bubble surface. Figure 11 presents the trend of buoyancy F b and Marangoni force F M varying with the bubble diameter, which was calculated from the force balance model.…”

Growth characteristics and the mass transfer mechanism of single bubble on a photoelectrode at different electrolyte concentrations

“…25 Baczyzmalski et al 26 generated magnetohydrodynamic convection caused by the Lorentz force in electrolyte solution by applying an external magnetic field, and pointed out that magnetohydrodynamic convection can enhance mass transfer near the working electrode and decrease the local concentration of the gas product, thereby accelerating the reaction and promoting the bubble detachment. Cao et al 27 adopted a periodic illumination system to study bubble evolution and found that this method can effectively increase the bubble detachment frequency and improve the mass transfer efficiency of the oxygen product compared with continuous illumination experiments. Wang et al 28 used a surfactant-assistant method and found that the addition of potassium perfluorobutyl sulfonate (PPFBS) in sulfuric acid electrolyte can improve the performance and strength of the gas evolution reaction (oxygen and hydrogen) by reducing the surface tension, thereby significantly accelerating the bubble detachment frequency and increasing the mass transfer efficiency on the working electrode.…”