Cu2O photoanode was fabricated using non-conductive epoxy resin (Loctite Epoxide-resin EA 9461 and EA 9466). First, Ag paste was applied to the ITO surface of the Cu2O substrate in a hollow square shape (0.1 ~ 0.12 cm 2 ), and a piece of Cu metal was connected to the squareshaped area using additional Ag paste. The extra surface outside the square area was blocked with opaque epoxy resin to ensure controlled light absorption. The Cu2O substrate was then placed on a glass slide with the back contact facing the glass, and the front layer was sealed with the epoxy resin again, leaving only the Ni surface (0.1 ~ 0.12 cm 2 ) aligned with the squareshaped area on the back contact exposed.