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

•Amorphous NiO co-catalysts are successfully loaded on g-C3N4.•The CONi linkages are formed at amorphous NiO/g-C3N4 heterojunctions.•Amorphous NiO modified g-C3N4 shows significantly enhanced H2 generation.•Amorphous NiO provide more active sites and allow effective light harvesting.•Amorphous NiO/g-C3N4 heterojunctions significantly promote the charge separation.

This study was mainly aimed at constructing an amorphous NiO modified g-C3N4 non-noble metal heterojunction 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 CONi linkages in the amorphous NiO/g-C3N4 heterojunctions are formed at NiO and g-C3N4 interface after annealing at 300 °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 H2 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 CONi linkages to amorphous NiO co-catalysts and thus significantly promoted the migration and separation of photogenerated charge carriers.

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