Preparation of Cu-doped TiO2 via refluxing of alkoxide solution and its photocatalytic properties

Surface Properties of 1DTiO2 Microrods Modified with Copper (Cu) and Nanocavities

This work deals with Cu-modified 1DTiO2 microrods (MRs) and their surface properties. The pristine lyophilized precursor Cu_1DTiO2, prepared by an environmentally friendly cryo-lyophilization method, was further annealed in the temperature interval from 500 to 950 °C. The microstructure of all samples was characterized by electron microscopy (SEM/EDS and HRTEM/SAED), X-ray powder diffraction (XRD), infrared spectroscopy, simultaneous DTA/TGA thermoanalytical measurement, and mass spectroscopy (MS). Special attention was paid to the surface structure and porosity. The 1D morphology of all annealed samples was preserved, but their surface roughness varied due to anatase-rutile phase transformation and the change of the nanocrystals habits due to nanocavities formation after releasing of confined ice-water. The introduction of 2 wt.% Cu as electronically active second species significantly reduced the direct bandgap of 1DTiO2 in comparison with undoped TiO2 and the standard Degussa TiO2_P25. All samples were tested for their UV absorption properties and H2 generation by PEC water splitting. We presented a detailed study on the surface characteristics of Cu doped 1DTiO2 MRs due to gain a better idea of their photocatalytic activity.

Facile fabrication of Fe-doped Nb2O5 nanofibers by an electrospinning process and their application in photocatalysis

It is of top priority to develop highly efficient visible-light photocatalysts to realize the practical applications of photocatalysis in industry. Niobium pentoxide (Nb2O5) is considered as a potentially attractive candidate for the visible-light-driven photodegradation of organic pollutants. In an effort to enhance its photocatalytic activity, Fe-doped Nb2O5 nanofibers with various Fe contents (the molar ratios of Fe to Nb were 0.005/1, 0.01/1, 0.03/1 or 0.05/1) were successfully prepared by an electrospinning method. The structural features, morphologies, and optical properties of the as-prepared samples were investigated. Photocatalytic activities of the samples were evaluated through degradation of Rhodamine B (RhB) under visible light irradiation. All the prepared Fe-doped Nb2O5 nanofibers exhibited much higher activities for degrading RhB solution than the pristine Nb2O5 nanofibers, and the maximum degradation yield of 98.4% was achieved with the nanofibers (Fe to Nb: 0.03/1) under visible light irradiation for 150 min. The photocatalytic degradation rate fitted a pseudo-first-order equation, and the rate constants of reactions with Fe-doped Nb2O5 nanofiber (the molar ratios of Fe to Nb were 0.03/1) or pure Nb2O5 nanofiber were 0.0282 min-1 and 0.0019 min-1, respectively. Doping Fe ions into the nanofibers enhanced the absorption within the visible-light range and reduced the photo-generated electron-hole pair recombination, and thus improved the photocatalytic activity. These attractive properties suggest that the Fe-doped Nb2O5 nanofibers have great potential for applications in the future to solve pollution issues.

Mechanistic Understanding on the Role of Cu Species over the CuO x /TiO2 Catalyst for CO2 Photoreduction

Incorporation of earth-abundant Cu is one of the most important approaches to improve the practicability of TiO2 for photoreduction of CO2 into value-added solar fuels. However, the molecular insight on the role of Cu is complicated and far from understood. We performed a first principle calculation on the anatase (101) surface modified by a single Cu atom deposited on the surface (CuS) or doped in the lattice (CuL). It is demonstrated the CuL is clearly more stable than the CuS and could promote the formation of oxygen vacancy (Vo) greatly. The CuS plays a role of donor, while the CuL is electronically deficient and becomes a global electron trapper. If a Vo is introduced, the excess electrons would immigrate to the empty gap state of the CuL and make it half-filled in some case, which implies its metallic characters and improved conductivity; meanwhile, the formation of Ti3+ is suppressed. Judging from the adsorption energies, it is the Vo that primarily improves the adsorption of CO2 in both linear and bent states, and the CuS could hardly stabilize CO2 more, while the promotion effect of Vo could even be counteracted by the CuL due to its electronic deficiency. The reduction pathways (CO2* → CO* + O*) show that, with the assistance of the CuS, linear CO2 could directly transform into the carbonate-like geometry vertically binding to the surface, and the intermediate configuration of the bent CO2 horizontally bridging the Vo could be successfully skipped. Therefore, the barrier of the rate-determining transformation could be lowered from 0.75 to 0.39 eV. Furthermore, it is found the strong adsorption of the produced CO by the CuS might retard the smooth going of the catalytic process.

Ternary Composite of Co-Doped CdSe@electrospun Carbon Nanofibers: A Novel Reusable Visible Light-Driven Photocatalyst with Enhanced Performance

In this work, flexible ternary composites of cobalt-doped cadmium selenide/electrospun carbon nanofibers (Co-CdSe@ECNFs) for photocatalytic applications were fabricated successfully via electrospinning, followed by carbonization. For the fabrication of the proposed photocatalysts, Co-CdSe nanoparticles were grown in situ on the surface of ECNFs during the carbonization of precursor electrospun nanofibers obtained by dispersing Se powder in the electrospinning solution of polyacrylonitrile/N,N-Dimethylformamide (PAN/DMF) containing Cd2+ and Co2+. The photocatalytic performance of synthesized samples is investigated in the photodegradation of methylene blue (MB) and rhodamine B (RhB) dyes. Experimental results revealed the superior photocatalytic efficiency of Co-CdSe@ECNFs over undoped samples (CdSe@ECNFs) due to the doping effect of cobalt, which is able to capture the photogenerated electrons to prevent electron–hole recombination, thereby improving photocatalytic performance. Moreover, ECNFs could play an important role in enhancing electron transfer and optical absorption of the photocatalyst. This type of fabrication strategy may be a new avenue for the synthesis of other ECNF-based ternary composites.

Construction of a novel ternary composite of Co-doped CdSe loaded on biomass carbon spheres as visible light photocatalysts for efficient photocatalytic applications

The cobalt doped cadmium selenide/biomass carbon spheres (Co-CdSe/BCS) photocatalyst is easily prepared using a transitory hydrothermal reaction lasting 40 min. The Co-CdSe/BCS photocatalyst is constructed using the in situ growth of Co-CdSe nanodots on the surfaces of the BCS. Doped Co2+ generates an electron trap, which can capture the photoinduced electrons, resulting in the efficient separation of the photoinduced electron-hole pairs. Furthermore, the introduction of carbon spheres enhances the optical absorption property and the ability for electron transport. Results of electrochemical characterization and photoluminescence spectra demonstrate that the Co-CdSe/BCS is able to efficiently separate electron-hole pairs and inhibit their recombination. The as-synthesized samples display high efficiency for the photodegradation of methylene blue dye under visible light. This study offers a new strategy to promote photocatalytic performance of the CdSe photocatalyst.

In Situ Probing of Photoinduced Hydrophilicity on Titania Surface Using Dye Molecules

The titania film surface exhibits superhydrophilicity after UV irradiation due to its photocatalytic function. This is caused by a change in the density of the surface hydroxyl groups, which affects the surface charge density. Titania films were prepared to observe the change in the surface charge during UV irradiation. The amounts of some xanthene dyes adsorbed and deposited on the titania films after UV irradiation were evaluated as a function of the irradiation time. The increase in the adsorption and deposition amounts of the more negative dye versus the UV irradiation time was greater. These results indicated that the titania surface charge became more positive by the UV irradiation. It was reported that basic hydroxyl groups formed on the titania particle surface during the UV irradiation. The surface dissociates hydroxyl ions into the water phase and has a positive charge, which was supported by the present study.

Visible Light-Driven high Photocatalytic Activity of Cu-Doped TiO2 Nanoparticles Synthesized by Hydrothermal Method

TiO2 and Cu-doped TiO2 nanoparticles (NPs) with totally extraordinary substance of Cu by exploitation hydrothermal method. The part immaculateness, morphology, molecule estimate, optical properties, and elemental composition of as-incorporated Cu-doped TiO2 NPs were investigated by numerous systematic methods. The XRD designs unveiled Cu-doped TiO2 NPs inside the part unadulterated anatase phase. The plane of (101) XRD and XPS results show the lucky doping of Cu2+ inside the TiO2 lattice. The optical edges of Cu-doped TiO2 demonstrated a transparent light absorption in visible region that assumes an essential part inside the photocatalytic action underneath characteristic daylight. Certain Cu2+ content shows least PL intensity that backings the decrease in recombination rate of charge species. In addition, to get a handle on photocatalytic action, we have tried Cu-doped TiO2 for the degradation of Malachite Green (MG) under visible light. A large portion of 85% degradation was found for Cu-doped TiO2 (1.71 wt.%) underneath daylight minimum of 180 min, severally, that is past that of TiO2 (53%). Also, the degradation of the MG was affirmed by measurement of the chemical oxygen demand of the photodegraded solution. These outcomes demonstrates that the Cu-doped TiO2 NPs are extremely productive for the photodegration of the MG.