A microfluidic all-vanadium photoelectrochemical cell for solar energy storage

In this work, a microfluidic all-vanadium photoelectrochemical cell (μVPEC) was designed for the solar energy storage. The miniaturization design could enhance the photon and mass transport, reduce the internal cell resistance, and improve the uniformity of the light distribution. Because of these advantages, the developed μVPEC was able to yield good performance. Experimental results indicated that the developed μVPEC showed good photoresponse and operation stability. Besides, its performance was also evaluated under various operating conditions, including the membrane thickness, the light intensity and the vanadium ion concentrations. It was shown that although the vanadium ion permeation was small with thicker membrane, the increased proton transfer resistance decreased the photocurrent density. The increase of the light intensity could produce more photo-generated electron-hole pairs, which could improve the photoelectrochemical reaction rate and the conversion rate. It was also found that the photocurrent density was increased with the vanadium ion concentration as a result of the enhanced mass transfer. The results obtained in this work reveal that the developed all-vanadium photoelectrochemical cell shows the promising potential for the solar energy storage.