Copper-Azolate Framework Coated on g-C3N4 Nanosheets as a Core-Shell Heterojunction and Decorated with a Ni(OH)2 Cocatalyst for Efficient Photoelectrochemical Water Splitting

A novel photoanode was designed using the Cu-azolate framework (CuAF) and g-C3N4 as a core-shell nano-composite (g-C3N4 gCuAF) decorated with a Ni(OH)(2) cocatalyst. The band structure of the g-C3N4 gCuAF composite presented a heterojunction of staggered-gap type II. The transfer of photo- generated electrons and holes to relative low-energy bands of CuAF and g-C3N4 prevents their recombination so that the photocurrent density of g-C3N4 gCuAF photoanode significantly increased compared to that of CuAF photoanode. The Ni(OH)(2) cocatalyst loaded on the photoanodes provided a facile path for photogenerated holes to split water molecules. The photoconversion efficiency of the g-C3N4 gCuAF/Ni(OH)(2) photoanode was 6 times greater than that of the pristine CuAF. The photovoltage of 290 mV for the g-C3N4 gCuAF/Ni(OH)(2) photoanode compared to 189 mV for the CuAF/Ni(OH)(2) photoanode indicates its deeper band bending. The g-C3N4 gCuAF/Ni(OH)(2) photoanode is stable under continuous light irradiation for 1 h.