title: Heterojunction engineering of graphitic carbon nitride (g-C3N4) via Pt loading with improved daylight-induced photocatalytic reduction of carbon dioxide to methane.
abstract: In this paper, noble-metal Pt nanoparticles of around 2.5 nm were deposited on graphitic carbon nitride (g-C3N4) synthesized by a chemical reduction process in ethylene glycol. Compared with pure g-C3N4, the resulting Pt-loaded g-C3N4 (Pt/CN) exhibited a considerable improvement in the photoreduction of CO2 to CH4 in the presence of water vapor at ambient temperature and atmospheric pressure under visible light irradiation. 2 wt% Pt-loaded g-C3N4 (2Pt/CN) nanocomposites produced the highest CH4 yield of 13.02 μmol gcatalyst(-1) after 10 h of light irradiation, which was a 5.1-fold enhancement in comparison with pure g-C3N4 (2.55 μmol gcatalyst(-1)). The remarkable photocatalytic activity of Pt/CN nanostructures in the CH4 production was ascribed to the enhanced visible light absorption and efficient interfacial transfer of photogenerated electrons from g-C3N4 to Pt due to the lower Fermi level of Pt in the Pt/CN hybrid heterojunctions as evidenced by the UV-Vis and photoluminescence studies. The enriched electron density on Pt favored the reduction of CO2 to CH4via a multi-electron transfer process. This resulted in the inhibition of electron-hole pair recombination for effective spatial charge separation, thus enhancing the photocatalytic reactions. Based on the experimental results obtained, a plausible mechanism for improved photocatalytic performance associated with Pt/CN was proposed.
authors.affiliation: Multidisciplinary Platform of Advanced Engineering, Chemical Engineering Discipline, School of Engineering, Monash University, Jalan Lagoon Selatan, Bandar Sunway, 47500 Selangor, Malaysia. chai.siang.piao@monash.edu.
authors.forename: Wee-Jun
authors.initials: WJ
authors.lastname: Ong
authors.forename: Lling-Lling
authors.initials: LL
authors.lastname: Tan
authors.forename: Siang-Piao
authors.initials: SP
authors.lastname: Chai
authors.forename: Siek-Ting
authors.initials: ST
authors.lastname: Yong