Xiaowei Hu

Diffusion-Controlled Growth of Oxygen Bubble Evolved from Nanorod-Array TiO2 Photoelectrode

Nanorod-array structure gains its popularity in photoelectrode design for water splitting. However, the structure’s effects on solid-liquid interface interaction and reaction product transportation still remain unsolved. Gas bubble generally evolved from photoelectrodes, which provides a starting point for the problem-solving. Based on this, investigations on the gas-evolving photoelectrode are carried out in this paper. By experimental studies of wettability on the photoelectrode nanorod-array surface and oxygen bubble growth from anode, we analyzed the interaction affecting the gas-solid-liquid contact behaviors and product transportation mechanism, which is controlled by diffusion due to the concentration gradient of dissolved gases in the aqueous electrolyte and the microconvection caused by the bubble interface movement. In the end, based on the bubble growth characteristics of in the experiment, a model describing the product transport mechanism was presented.

In Situ Measurement of Local Hydrogen Production Rate by Bubble-Evolved Recording

Hydrogen visibly bubbles during photocatalytic water splitting under illumination with above-bandgap radiation, which provides a direct measurement of local gas-evolving reaction rate. In this paper, optical microscopy of superfield depth was used for recording the hydrogen bubble growth on Cd0.5Zn0.5S photocatalyst in reaction liquid and illuminated with purple light. By analyzing change of hydrogen bubble size as a function of time, we understood that hydrogen bubble growth experienced two periods, which were inertia effect dominated period and diffusion effect dominated period, respectively. The tendency of hydrogen bubble growth was similar to that of the gas bubble in boiling, while the difference in bubble diameter and growth time magnitude was great. Meanwhile, we obtained the local hydrogen production rate on photocatalyst active site by measuring hydrogen bubble growth variation characteristics. This method makes it possible to confirm local actual hydrogen evolution rate quantitatively during photocatalytic water splitting.

Lagrangian numerical simulation for solid-liquid two-phase flow in a curved duct

A multiway coupling Lagrangian model was developed and used to simulate the solid-liquid two-phase flow in a curved duct. Particle-wall collision and interparticle collision were included by hard sphere model and stochastic collision model. Comparison between experimental results and numerical simulation shows a reasonable agreement. The effects of liquid mean velocity, curvature radius and section shape of a curved duct on particle volume concentration distribution were investigated by this model and a new ideal for separation enhancement between liquid and solid was proposed.

Measurement of Interfacial Area Transport in Oil‐water Dispersed Flow by Double‐sensor Probe

The double‐sensor conductivity probe was designed and applied to measure the distribution and transport characteristics of the oil‐water dispersed flow in a vertical upward pipe. Typical radial profiles of interfacial area concentration, oil phase fraction, interfacial velocity, and oil drop Sauter mean diameter were obtained at four axial locations from the test section entrance of z/D =8.75, 33.75, 58.5 and 80.5. The results showed that under most flow conditions, the radial profiles of interfacial area concentration, oil phase fraction and interfacial velocity at the first measuring location were more flat than those at other three locations. This is because the initial size of oil drops were mainly determined by the mixing chamber and the flow of oil‐water dispersion were far from fully‐development. The interfacial area transport mechanism was also discussed in details.