To improve the performance of 3C-SiC photocathodes, we formed a pn junction at the 3C-SiC surface. Using current voltage measurements for Schottky contacts on 3C-SiC, the Schottky barrier height and depletion layer width of 3C-SiC having a pn junction was observed to be larger than those of 3C-SiC without the junction. By measuring photo current and spectral responses, the 3C-SiC photocathodes with the pn junction exhibited larger photocurrent and higher quantum efficiencies compared with 3C-SiC without the pn junction. Using a Pt cocatalyst on the 3C-SiC photocathode with the pn junction, the solar-to-hydrogen energy conversion efficiency was measured at 0.72%. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.