A scalable optofluidic microreactor with immobilized Pt–CdS catalysts for visible light-driven photocatalytic hydrogen evolution from water

Abstract

Addressing climate change, environmental pollution, and escalating energy demand requires a global shift toward renewable energy alternatives. Green hydrogen, produced through photocatalytic water splitting, offers a promising alternative; however, the efficiency and scalability of existing systems remain limited. This study introduces a scalable, efficient, and cost-effective optofluidic microreactor system for visible-light-driven photocatalytic hydrogen evolution from water, fabricated using a cheap laser-lithography-assisted wet chemical etching process. The CdS nanowire photocatalysts, synthesized via a solvothermal method and modified with a Pt cocatalyst, were immobilized on the microreactor walls by a spray coating method using colloidal silica as a binder. A parametric study is conducted to optimize the reactor plate fabrication and catalyst coating, resulting in an optimized system. The optofluidic device with optimum design produced hydrogen gas bubbles at a maximum rate of 60.7 μmol h⁻¹ (1.21 mmol g⁻¹ h⁻¹ mass-normalized, 12.48 mmol m⁻² h⁻¹ area-normalized) under 250 W LED lamp illumination. The apparent quantum yield (AQY) of the optimized system for hydrogen evolution was calculated to be 0.11% in the wavelength range of 400 to 700 nm. The potential scalability of the optofluidic microreactor system was discussed in the context of large-area reactor fabrication, highlighting its prospective application in practical solar hydrogen production.