Water oxidation is a 4-electron uphill energy process that largely limits the overall water splitting reaction thermodynamically and kinetically[1].Photocurrent measurement is one of the most important approaches to evaluate the performance of a photoanode.It has been well realized that photocurrent may render exaggerated performance when Water oxidation is a 4-electron uphill energy process that substantial limits the overall water splitting reaction thermodynamically and kinetically [1]. Photocurrent measurement is one of the most important approaches to evaluate the performance of a photoanode. It has been well realized that photocurrent may render exaggerated performance when