Heterojunction nanoarchitectonics of WOx/Au-g-C3N4 with efficient photogenerated carrier separation and transfer toward improved NO and benzene conversion

Abstract

Topics on effectively improving the photochemical CO2/benzene/NO oxidation conversion performances of g-C3N4 based materials via charge transfer and separation enhancement are still considered challenging, despite the growing popularity of applying these materials in a variety of energy conversion related applications. Based on the idea of nanoarchitectonics, a post-nanotechnology concept, WOx/Au-g-C3N4 heterostructures are synthesized using two-step thermal polymerization and solvothermal treatment methods in this paper. Small Au nanoparticles are incorporated in superior thin g-C3N4 via mechano-chemical pre-reaction and two-step thermal polymerization (treated at 500 and 700 °C). Enhanced photocurrent density is observed after incorporation of Au, which is also in good agreement with the photocatalytic activity (H2 generation and CO2 reduction) data. Layered WOx with abundant oxygen vacancies are further incorporated into Au-modified g-C3N4 nanosheets to form heterojunctions possessing excellent photocatalytic CO2 photo-reduction performances with CO and CH4 generation rate of 5.64 and 2.58 μmolg−1h−1, respectively, under full solar spectrum. The heterojunctions constructed via in-situ formation show direct Z-scheme charge transfer pathway with improved charge separation and transport efficiencies. These highly stable and recyclable hierarchical g-C3N4 hybrid nanostructures (WOx/Au-g-C3N4 heterojunctions) show outstanding conversion rate (88.1%) and selectivity (99.3%) for benzene to phenol conversion under full solar spectrum condition, as well as excellent NO removal rate (61%).