Optofluidic microreactor for the photocatalytic water splitting to produce green hydrogen

Abstract

The microfluidic devices can effectively be used for the renewable energy conversion, such as solar to chemical (e.g., H2) energy, to meet the global energy demand. The microchannel design plays a vital role in improving the mass transfer in photocatalytic processes. In this study, a simple, rapid, and inexpensive adhesive tape-based method was used to fabricate the serpentine, planar and micropillared optofluidic microreactors with sharp edges without any wall irregularities. The sol-gel method was used for the CdS catalyst coating in the microreactors. The effect of liquid flow rate (0.05–1 mL min−1) and sacrificial reagent (Na2SO3/Na2S) concentration (0.05–0.5 M) on the hydrogen generation under visible light was studied. A higher H2 production rate was observed in the serpentine microreactor as compared to that in planar and micropillared microreactors. The serpentine microreactor, having higher surface-to-volume ratio, induced the micromixing that enhanced the mass transfer of the sacrificial reagent and formed H2 gas. A maximum H2 production rate of 2.65 μmol h−1 cm−2 was observed at a flow rate of 1.0 mL min−1 and a sacrificial reagent concentration (Na2SO3/Na2S) of 0.5 M. The new approach developed in this study is a step forward in fabricating highly efficient and inexpensive optofluidic microdevices for the hydrogen production from solar energy.