摘要
This work demonstrates how to set efficiency benchmarks in photo-electrochemical measurements for solar water splitting with assistance of voltage biases. We modify the applied bias photon-to-current efficiency to circumvent the existing limitations for precisely estimating the energy transformation efficiency under valid conditions. The light sources, surface area of counter electrodes, and oxygen content in electrolytes, and photo-anode materials are changed to investigate their impact on the energy transformation efficiency. This work clarifies that a larger counter electrode surface area results in the enhancement of the oxygen reduction reaction, reducing the applied bias voltage but also reducing the hydrogen generation rate. Furthermore, positive potential biases on the photo-anode and removal of dissolved oxygen molecules in the electrolyte are effective to promote the hydrogen generation rate because of efficient electron/hole separation and the ORR elimination. Due to the high photocurrent generated by the ultraviolet light source, the consumption of photocurrents by the ORR is generally negligible. Therefore, a balance between photocurrent and applied potential bias on the photo-electrochemical cell is proposed to achieve the desired energy transformation efficiency.