A photocatalytic planar reactor with an immobilized nanoporous BiVO4 film has been integrated with a blue-light panel LED, which acts as the light source. The microreactor utilizes two BiVO4-coated glasses as the top and the bottom layer and a UV curable resin layer as the spacer. The UV spacer is patterned with tree-shaped microchannels and a reaction chamber (10 ´ 10 ´ 0.1 mm3). It was found that under blue light of 140 mW/cm2 (the LED is powered at 11 V, 402 nm ) and the flow rate of 37.5 µl/min, the microreactor has the optimum performance with a degradation rate of about 3%/s and a photonic utilization efficiency ³ 0.02%. However, the photonic efficiency can be improved to 0.3% when LED is powered at 9 V.