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In this work, the condensation behaviors of distilled water actuated by photothermal effect of the infrared laser with the wavelength of 1550 nm in a microchannel were investigated through the visualization method and image processing technique. The impacts of the laser power and the laser spot position on the interface movement and slug formation were also explored. It is found that the interface tended to be advanced as a result of the photothermally induced evaporation–condensation–coalescence process at lower laser powers while the interface was firstly advanced at the beginning and then moved backward after the liquid slug formation in front of the interface at high laser powers. Experimental results also showed that higher laser power and smaller distance between the initial gas–liquid interface and fixed laser spot yielded faster advancing of the gas–liquid interface. For cases with the liquid slug formation, the growth rate of the liquid slug increased with increasing the laser power and decreasing the distance of the laser spot position away from the initial interface position as a result of a high evaporation rate. [ABSTRACT FROM AUTHOR]

In this study, a novel mesoporous CdS/TiO 2 /SBA-15@carbon paper composite membrane was developed to enhance the visible-light responsive CO 2 photoreduction in an optofluidic membrane microreactor. The microscopic morphological and pore volume characterizations indicated that the incorporation of the mesoporous SBA-15 into the membrane development could greatly improve the specific surface area and pore volume. The optofluidic membrane microreactor with the newly-developed composite membrane was evaluated in terms of the methanol concentration and yield. Experimental results showed that the optofluidic membrane microreactor with mesoporous CdS/TiO 2 /SBA-15@carbon paper composite membrane yielded much better performance than did the one without the mesoporous SBA-15. For a given total amount of TiO 2 /SBA-15 in the composite membrane, too high dosage of TiO 2 in the composite membrane caused the reduction in the specific surface area and pore volume, thereby lowering the photocatalytic performance. In addition, it was found that the methanol concentration and yield firstly increased and then decreased with increasing the liquid flow rate. The increase of both the light intensity and NaOH concentration was able to enhance the methanol generation. The obtained results fully demonstrate the superiority of the newly-developed CdS/TiO 2 /SBA-15@carbon paper composite membrane for the CO 2 photoreduction. [ABSTRACT FROM AUTHOR]

The development of highly efficient photocatalytic reactor is of importance to improve the performance of the photocatalytic reduction of CO 2 . In this work, an optofluidic planar microreactor is designed and fabricated for the photocatalytic reduction of CO 2 with liquid water in alkaline environment. Such design offers several advantages of large surface-area-to-volume ratio, enhanced mass and photon transfer and more uniform light distribution. The performance of the developed planar microreactor is evaluated by measuring the methanol concentration to estimate the methanol yield under various operating parameters, including the liquid flow rate, light intensity, catalyst loading and NaOH concentration. It is shown that increasing the liquid flow rate firstly improves and then decreases the methanol concentration while the methanol yield continuously increases as the liquid flow rate increases. The increase of the light intensity and NaOH concentration increases both the methanol concentration and yield. Increasing the catalyst loading firstly improves the performance and then results in the reduction of the performance. A maximum methanol yield of 454.6 μmole/g-cat·h is achieved under a liquid flow rate of 50 μL/min, 0.2 M NaOH, and the light intensity of 8 mW/cm 2 . [ABSTRACT FROM AUTHOR]

Photocatalytic reduction of CO 2 is a promising technology to capture CO 2 and convert it into solar fuels simultaneously. However, current photoreactors usually face the problems of low specific surface area, non-uniform light distribution and poor photon transfer. To address these issues, a novel optofluidic membrane microreactor with high surface-area-to-volume ratio, enhanced photon and mass transport and uniform light distribution was proposed in this work by combining optofluidics with the membrane reactor technology for the photocatalytic reduction of CO 2 with liquid water. A TiO 2 /carbon paper composite membrane was prepared as the photocatalytic membrane via coating TiO 2 onto the carbon paper followed by hydrophobic treatment by poly-tetrafluoroethylene (PTFE) for the separation of the gas/liquid phases. The performance of the proposed optofluidic membrane microreactor was evaluated by measuring the methanol yield. The effects of the liquid water flow rate, light intensity and catalyst loading on the methanol yield were also studied. It was shown that a maximum methanol yield of 111.0 μmole/g-cat·h was achieved at a flow rate of 25 μL/min and under the light intensity of 8 mW/cm 2 , which is among the top in comparison to the reported data. Results obtained fully demonstrate the feasibility and superiority of the proposed optofluidic membrane microreactor for the photocatalytic reduction of CO 2 . [ABSTRACT FROM AUTHOR]

In this work, the characteristics of the meniscus evaporation from a microchannel were studied, which was induced by the photothermal effect of the infrared laser with the wavelength of 1550 nm. The evaporation rate and mass transfer coefficient at the interface were determined by the proposed image process technique coupled with an infrared camera. Experimental results showed that once the infrared laser was applied, the interface temperature was rapidly increased but with non-uniform distribution as a result of such a tiny local heating source. Accompanying with the rapid temperature rise, the meniscus evaporation was also immediately actuated. After a certain laser heating period, the interface temperature was increased to a stable value with relatively uniform distribution. In the meantime, the evaporation rate increased and became steady. Besides, the effects of the laser power and laser spot position on the evaporation rate and mass transfer coefficient at the interface were also explored. It was shown that both the interface temperature and evaporation rate linearly increased with the laser power as a result of more heat generated. Smaller distance between the laser spot and front interface yielded higher interface temperature and evaporation rate because of smaller heat transfer resistance resulting from smaller transport length. Reducing the distance could make the increase of the evaporation rate to become more significant. With respect to the mass transfer coefficient, it is interesting to find that the mass transfer coefficients under all cases were almost the same, about 0.4 m/s. [ABSTRACT FROM AUTHOR]