474228 Fabrication of CoTiO3/g-C3N4 Hybrid Photocatalysts with Enhanced H2 Evolution

Tuesday, November 15, 2016: 5:15 PM
Union Square 21 (Hilton San Francisco Union Square)
Xia Tao and Yan-Zhen Zheng, Beijing University of Chemical Technology, Beijing, China

Hydrogen (H2) has gained much attention as a sustainable and carbon-neutral fuel carrier. Since Fujishima and Honda reported H2 evolution from water splitting by using TiO2 electrode under light irradiation in 1972, photocatalytic water splitting has become one of the most fascinating and promising technologies. Among numerous photocatalysts, graphitic carbon nitride (g-C3N4) has been rapidly developed due to its non-toxic, proper energy band level for H2 production (2.7 eV), ability of absorbing visible light, good physicochemical stability and facile fabrication via one-step polymerization. Unfortunately, the pure g-C3N4 seriously suffers from poor photocatalytic efficiency because of a high recombination rate of photo-generated charge carriers. To settle this problem, g-C3N4-based heterojunctions were prepared. However, the redox ability of photoexcited electrons and holes would be declined as the typical heterojunction forms.

This work reports a novel direct Z-scheme CoTiO3/g-C3N4 (CT-U) photocatalytic system with different weight percentage of CoTiO3 using a facile in-situ growth method for H2 evolution from water splitting. The as-prepared CT-U composites composed of 1D CoTiO3 microrod and 2D g-C3N4 nanosheet were characterized by various techniques including XRD, SEM, TEM, XPS, FTIR and UV-vis. Results demonstrate that the CT-U composite photocatalysts were successfully fabricated, with intimate interfacial contact and heterojunction interaction between g-C3N4 and CoTiO3 which can significantly boost the photocatalytic activity compared with prinstine g-C3N4 and CoTiO3. The most enhanced H2 evolution rate of 858 μmol·h-1·g-1 and high quantum efficiency (38.4% at 365 nm, 3.23% at 420 ± 20 nm) are achieved at an optimal 0.15% CT-U. Meanwhile, the 0.15% CT-U sample exhibits good photocatalytic stability in recycling H2 evolution. Accordingly, direct Z-scheme mechanism capable of leading efficient charge carrier separation and strong reduction ability for enhanced H2 production was proposed, and further evidenced by PL, Photoelectrochemical analysis and ESR assay.

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