Insight into the Roles of Metal Loading on CO2 Photocatalytic Reduction Behaviors of TiO2

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.

Effects of Pd and Co intimacy in Pd-modified Co/TiO2 catalysts for direct CO2 hydrogenation to fuels: the closer not the better

“…S5†), it can be concluded that compared to the support, the 1Pd/ catalyst binds CO 2 more strongly, since all the peaks are shifted to higher temperatures. Such a phenomenon has already been reported for Pd/TiO 2 45 and Pt/TiO 2 catalysts, 46,47 suggesting an increased surface basicity upon noble metal addition. The peak at around 100 °C has been attributed to the desorption signal of CO 2 weakly interacting with the TiO 2 support (weak surface basic sites).…”

“…S5 †), it can be concluded that compared to the TiO 2 * support, the 1Pd/TiO 2 * catalyst binds CO 2 more strongly, since all the peaks are shifted to higher temperatures. Such a phenomenon has already been reported for Pd/TiO 2 45 and Pt/TiO 2 catalysts, 46,47 suggesting an 46 This might be due to a decrease of adsorption sites (O v and surface Na) after Pd deposition. It is nevertheless important to note that the presence of Pd during catalysis may lead to the generation of O v and Ti 3+ sites on the support, which are favorable for strong or medium adsorption of CO 2 .…”

“…Quantification of the CO 2 -TPD results (Table S1†) shows that the catalyst adsorbs less CO 2 than the support, as already reported for Pt/TiO 2 catalysts. 46 This might be due to a decrease of adsorption sites (O v and surface Na) after Pd deposition. It is nevertheless important to note that the presence of Pd during catalysis may lead to the generation of O v and Ti 3+ sites on the support, which are favorable for strong or medium adsorption of CO 2 .…”

TiO2–Ag–NP adhesive photocatalytic films able to disinfect living indoor spaces with a straightforward approach

“…It is well known that upon UV light irradiation, for example UV components from direct solar light, only the semiconductor, i.e., TiO 2 , is excited. In this circumstance, to improve the photocatalytic potential of a product with TiO 2 , doping the photocatalytic material with metal nanoparticles, allows these latter to act as a kind of sink for electrons induced by light photons, via the Schottky barrier, a condition that prolongs the lifespan of these electrons, by reducing the recombination rate 52,53 .…”

Rhenium(I) Complex-Containing Amphiphilic Metallopolymer Stabilizing CdS Quantum Dots for Synergistically Boosting Photoreduction of CO2

“…Photocatalytic CO 2 reduction has been extensively studied with a range of materials, including semiconductor quantum dots, , metal-oxide semiconductors, graphene and its derivatives, , graphitic carbon nitride ( g -C 3 N 4 ), , framework materials, , and transition metal complexes , as well as their composites. , Among these materials, semiconducting CdS quantum dots (QDs) have emerged as highly effective catalysts for light-driven CO 2 reduction due to their unique properties, which allow simple modulation of energy band gaps by varying dot sizes, compositions, and capping agents. This characteristic maximizes solar light absorption and electron transfer. , In addition, intrinsic quantum confinement effects endow CdS QDs with tunable redox potential and photoreduction selectivity .…”