Strategies of Spatial Deposition of Cocatalysts for the Efficient Photocatalytic Abatement of Micropollutants

Description

The proposal introduces a new concept on the spatial decoration of cocatalysts onphotocatalysts that essentially allows the decoupling of Schottky barrier effect and thatfor surface charge transfer. This is to be achieved by spatially segregating thecocatalysts for each role and in an independent fashion. Cocatalysts with high workfunctions (Pt, Ir, Pd, Au) are to be deposited directly on the photocatalysts surface tomaximise the charge separation across the Schottky barrier. The electron transfercocatalysts (Pt, Ag, Pd/Co, Au/Pd and Ni/Fe) will be predeposited onto reduced grapheneoxide prior to the attachment of the two components. To harness the wide spectrum ofthe solar irradiation, a range of wide and mid-bandgap oxide photocatalysts withsuitable conduction band potentials (TiO2, SrTiO3, WO3, Ag3PO4, Ag3VO4, Bi2WO6, andBiVO4) will be synthesised and assessed as the base substrate for decoration withcocatalysts. Photocharge transport and the physicochemical properties will becharacterized to verify the working mechanism of the advanced compositephotocatalysts.The spatial deposition allows the selection of the best combinations of rationalcocatalysts in surpassing the efficiencies of the conventional (but yet unsurpassed)single metal-deposited photocatalysts that practices the philosophy of “one cocatalystfits all”. As such, the proposed strategy is a paradigm shift in terms of the architectureof high efficiency photocatalysts. In this proposal, the composite photocatalysts will bespecifically designed for the solar abatement of a range of endocrine disruptors andantibiotics. Besides being emerging micropollutants with relevant global and regionalconcerns, the target substrates were carefully chosen to allow the studies of the efficacyof the photocatalysts in targeting certain molecular functional groups. Assessments willalso be carried out as a function of water conditions, that is, water hardness, anions andcations, as well as the humic acid concentrations.Based on the laboratory-derived data and the measurement of action spectra of thephotocatalysts, it will be possible to rationally construct the “rainbow photocatalysts” thatmaximize the coverage of the solar spectrum. Based on this, an outdoor reactor with flowover photocatalysts-coated corrugated plates will be constructed to showcase theabatement of the micropollutants to be assessed in real water samples collected fromreservoirs in Hong Kong. The reactor will be engineered to maximize external andinternal mass (reactants and products) diffusions into and out of the porousphotocatalyst layer, effectiveness factor as well as solar light penetration.