Microfluidic-enhanced 3-D photoanodes with free interfacial energy barrier for photoelectrochemical applications

The sluggish reaction kinetics and poor interfacial mass transfer seriously limit the industrial applications of planar photoelectrocatalytic devices. Here, the principle of 3-D flow-through photoanodes with free interfacial barrier for electron transfer and microfluidic channels for reactant transportation was demonstrated. Owing to the epitaxial growth of anisotropic ZnO nanorods with internal electrostatic field onto carbon cloth (CC), the spatial separation of photo-induced charge carriers was realized. Experimental characterizations confirmed the formation of Schottky-barrier-free interface with low electrical resistance for electron transfer, resulting in the significantly decreased onset potential. Compared to traditional planar FTO/ZnO photoanodes, flow-through CC/ZnO photoanodes exhibited 4 times (for Rhodamine B) and 3 times (for bisphenol A) higher degradation kinetics. Fluid dynamics simulation suggested that the flow-through mode greatly enhanced the microscale velocity magnitude and the mass transfer of reactants. Thus, this work presents an ideal platform for the design of 3-D microfluidic-enhanced system for photoelectrochemical applications.