Z-scheme WOx/Cu-g-C3N4 heterojunction nanoarchitectonics with promoted charge separation and transfer towards efficient full solar-spectrum photocatalysis

Abstract

Construction of Z-scheme heterojunctions has been considered one superb method in promoting solar-assisted charge carrier separation of carbon-based materials to achieve efficient utilization of solar energy in hydrogen production and CO2 reduction. One interesting concept in nanofabrication that has become trend recent years is nanoarchitectonics. A heterostructure photocatalyst constructed based on the idea of nanoarchitectonics using the combination of g-C3N4, metal and an additional semiconducting nanocomposite is investigated in this paper. Z-scheme tungsten oxide incorporated copper modified graphitic carbon nitride (WOx/Cu-g-C3N4) heterostructures are fabricated via immobilization of WOx on Cu nanoparticles modified superior thin g-C3N4 nanosheets. Mechano-chemical pre-reaction and a two-step high-temperature thermal polymerization process are the keys in attaining homogeneous distribution of Cu nanoparticles in g-C3N4 nanosheets. The horizontal growth of homogeneously distributed WOx nanobelts on Cu modified g-C3N4 (Cu-g-C3N4) base via solvothermal synthesis is achieved. The photocatalytic performances of the heterostructures are evaluated through water splitting and CO2 photoreduction measurements in full solar spectrum irradiation condition. The presence of Cu nanoparticles in the composite system improves charge transport between g-C3N4 and WOx and thus enhances the photocatalytic performances (H2 generation and CO2 photoreduction) of the composite material, while the presence of WOx nanocomposites enhances light absorption of the composite material in the near infrared range. The synthesized heterostructure with optimized WOx to Cu-g-C3N4 ratio and in case of no co-catalyst addition exhibits enhanced photocatalytic H2 evolution (4560 μmolg-1h−1) as well as excellent CO2 reduction rate (5.89 μmolg-1h−1 for CO generation).