where iph is the photocurrent density, h is Planck's constant, c is the velocity of light, P is the light power density, λ is the irradiation wavelength, and q is the elementary charge. The electrolyte for all photoelectrochemical measurements was 0.1 M sodium borate electrolyte with pH value of 8.0. Na2SO3 (0.1 M) was dissolved in the electrolyte when photocurrents were measured in the presence of sacrificial electron donor. All potentials are recalculated and reported vs. RHE.