Abstract
The photocatalytic reduction of carbon dioxide (CO2) into value-added chemicals is considered to be a green and sustainable technology, and has recently gained considerable research interest. In this work, titanium dioxide (TiO2) supported Pt, Pd, Ni, and Cu catalysts were synthesized by photodeposition. The formation of various metal species on an anatase TiO2 surface, after ultraviolet (UV) light irradiation, was investigated insightfully by the X-ray absorption near edge structure (XANES) technique. CO2 reduction under UV-light irradiation at an ambient pressure was demonstrated. To gain an insight into the charge recombination rate during reduction, the catalysts were carefully investigated by the intensity modulated photocurrent spectroscopy (IMPS) and photoluminescence spectroscopy (PL). The catalytic behaviors of the catalysts were investigated by density functional theory using the self-consistent Hubbard U-correction (DFT+U) approach. In addition, Mott–Schottky measurement was employed to study the effect of energy band alignment of metal-semiconductor on CO2 photoreduction. Heterojunction formed at Pt-, Pd-, Ni-, and Cu-TiO2 interface has crucial roles on the charge recombination and the catalytic behaviors. Furthermore, it was found that Pt-TiO2 provides the highest methanol yield of 17.85 µmol/gcat/h, and CO as a minor product. According to the IMPS data, Pt-TiO2 has the best charge transfer ability, with the mean electron transit time of 4.513 µs. We believe that this extensive study on the junction between TiO2 could provide a profound understanding of catalytic behaviors, which will pave the way for rational designs of novel catalysts with improved photocatalytic performance for CO2 reduction.
Highlights
The severe adverse effects of global warming resulting from excessive carbon dioxide (CO2 ) emission arouses the need for urgent research into CO2 reduction
The roles of loading metals, including Pt/TiO2 −5.65 (Pt), Pd/TiO−2 5.22 (Pd), Ni/TiO−2 5.04 (Ni), and Cu, prepared by photodeposition on TiO2 towards the photocatalytic reduction of CO2 are investigated in many aspects simultaneously, in order to gain an insight into true catalytic behavior
TiO2 loaded with various metals (Pt, Pd, Ni, and Cu) was successfully synthesized by photodeposition method
Summary
The severe adverse effects of global warming resulting from excessive carbon dioxide (CO2 ) emission arouses the need for urgent research into CO2 reduction. Insights into the interaction of adsorbed CO2 with the semiconductor-modified surface as the catalytic sites are still expected to be further explored as the structure and the cation sites on the modified Ti surface composition are involved in the catalytic pathways and selectivity of products They can lower the reaction barrier to activate CO2 , and stabilize CO2 intermediates to enhance CO2 photoreduction. The roles of loading metals, including Pt, Pd, Ni, and Cu, prepared by photodeposition on TiO2 towards the photocatalytic reduction of CO2 are investigated in many aspects simultaneously (i.e., band alignment, plasmonic effects, charge recombination, charge transfer, and surface chemistry), in order to gain an insight into true catalytic behavior. The impressive performance is attributed to suppressed charge recombination, suitable band alignment, and appropriate surface chemistry
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