Optofluidic microreactor for the photocatalytic water splitting to produce green hydrogen

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.