Amorphous NiO as co-catalyst for enhanced visible-light-driven hydrogen generation over g-C3N4 photocatalyst

This study was mainly aimed at constructing an amorphous NiO modified g-C3N4 non-noble metal hetero-junction photocatalyst for enhanced visible-light hydrogen evolution. The Ni species modified g-C3N4 sample was firstly prepared through the wetness impregnation method and then the phase and crystallinity of Ni species co-catalysts on g-C3N4 were adjusted by the thermal oxidation at different temperature. The detailed characterizations revealed that the amorphous NiO co-catalysts are supported successfully on g-C3N4, and the C-O-Ni linkages in the amorphous NiO/g-C3N4 heterojunctions are formed at NiO and g-C3N4 interface after annealing at 300 degrees C. Compared to bare g-C3N4 and crystalline NiO modified g-C3N4 photocatalysts, amorphous NiO modified g-C3N4 non-noble metal photocatalyst showed significantly enhanced visible-light photocatalytic hydrogen production activity. The amorphous NiO co-catalysts provided more active sites for H-2 evolution and amorphous NiO modification caused the enhanced visible-light response. Moreover, amorphous NiO/g-C3N4 heterojunctions formed at interface between amorphous NiO and host g-C3N4 created an inner electric field, which allowed for the transfer of the photogenerated electrons of g-C3N4 across the interfacial C-O-Ni linkages to amorphous NiO co-catalysts and thus significantly promoted the migration and separation of photogenerated charge carriers.