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Metal/oxide support perimeter sites are known to provide unique properties because the nearby metal changes the local environment on the support surface. In particular, the electron scavenger effect reduces the energy necessary for surface anion desorption, thereby contributes to activation of the (reverse) Mars-van Krevelen mechanism. This study investigated the possibility of such activation in hydrides, carbides, nitrides, and sulfides. The work functions (WFs) of known hydrides, carbides, nitrides, oxides, and sulfides with group 3, 4, or 5 cations (Sc, Y, La, Ti, Zr, Hf, V, Nb, and Ta) were calculated. The WFs of most hydrides, carbides, and nitrides are smaller than the WF of Ag, implying that the electron scavenger effect may occur when late transition metal nanoparticles are adsorbed on the surface. The WF of oxides and sulfides decrease when reduced. The surface anion vacancy formation energy correlates well with the bulk formation energy in carbides and nitrides, while almost no correlation is found in hydrides because of the small range of surface hydrogen vacancy formation energy values. The electron scavenger effect is explicitly observed in nanorods adsorbed on TiH2 and Ti2O3; the surface vacancy formation energy decreases at anion sites near the nanorod, and charge transfer to the nanorod happens when an anion is removed at such sites. Activation of hydrides, carbides, and nitrides by nanorod adsorption and screening support materials through WF calculation are expected to open up a new category of supported catalysts., Supplementary material available at https://doi.org/10.1039/D1CP02068D

Synergistic nitrogen reduction and water oxidation process is significant to the photocatalytic fixation of nitrogen. However, the coupling mechanism remains ambiguous and lacks study. Herein, we r...

Photodriven nonoxidative coupling of CH 4 (NOCM) is an attractive potential way to use abundant methane resources. Herein, a n-type doped photocatalyst for NOCM is created by doping single-atom Nb into hierarchical porous TiO 2 -SiO 2 (TS) microarray, which exhibits a high conversion rate of 3.57 μmol g -1 h -1 with good recyclability. The Nb dopant replaces the 6-coordinated titanium on the (1 0 1) surface and forms shallow electron-trapped surface polarons along [0 1 0] direction as verified by the experimental analyses and the first-principle density functional theory calculation. The comparison of different models proves that the electron localization caused by the n-type doping is beneficial to both the methane activation and ethane desorption. The positive effect of n-type dopant on CH 4 conversion is further verified on Mo-, W- and Ta-doped composites. In contrast, the doping of p-type dopant (Ga, Cu, Fe) shows less active influence. This study provides an in-depth insight into the effect of dopant type and is expected to guide the smart photocatalyst design for CH 4 conversion.

Introduction of linker defects in a visible light responsive metal–organic framework (MOF) photocatalyst, MIL-125(Ti)–NH2, has been attempted to improve its reactivity. MIL-125(Ti)–NH2, composed of Ti-oxo cluster and 2-aminoterephthalic acid organic linker, was synthesized by a solvothermal method and then underwent photothermal treatments. XRD measurements and 1H NMR spectroscopy revealed that linker elimination from the MOF occurred by a simultaneous visible-light irradiation and mild heating at 313 K in water containing electron donor, while keeping its framework structure. The resultant defective MOF effectively promotes visible light-driven H2 evolution reaction from water containing electron donor without using any cocatalysts, and its activity is comparable to that of Pt cocatalysts-loaded crystalline MIL-125(Ti)–NH2. When pristine MIL-125(Ti)–NH2 without cocatalysts is used in the reaction, the reduction of Ti species in Ti-oxo clusters from Ti4+ to Ti3+ takes place instead of reducing protons to evolve H2; thereby, linker defect introduction caused by the photothermal treatment was concluded to play a role in creating effective reaction sites for proton reduction on Ti-oxo clusters.

3D-MoS2 can adsorb organic molecules and provide multidimensional electron transport pathways, implying a potential application for environment remediation. Here, we study the degradation of aromatic organics in advanced oxidation processes (AOPs) by a 3D-MoS2 sponge loaded with MoS2 nanospheres and graphene oxide (GO). Exposed Mo4+ active sites on 3D-MoS2 can significantly improve the concentration and stability of Fe2+ in AOPs and keep the Fe3+ /Fe2+ in a stable dynamic cycle, thus effectively promoting the activation of H2 O2 /peroxymonosulfate (PMS). The degradation rate of organic pollutants in the 3D-MoS2 system is about 50 times higher than without cocatalyst. After a 140 L pilot-scale experiment, it still maintains high efficiency and stable AOPs activity. After 16 days of continuous reaction, the 3D-MoS2 achieves a degradation rate of 120 mg L-1 antibiotic wastewater up to 97.87 %. The operating cost of treating a ton of wastewater is only US$ 0.33, suggesting huge industrial applications.

This work spotlights the facile method to deposit cobalt oxide (CoOx) nanoparticles as a cocatalyst on Fe-MOF-bpdc to enhance its photocatalytic activity for water oxidation reaction (WOR) under visible light irradiation to evolve gaseous O2. Due to the soft conditions needed for the process developed, the framework structure of Fe-MOF-bpdc was maintained even after the deposition of CoOx. The optimized CoOx@Fe-MOF-bpdc composite showed enhanced activity towards visible-light-driven WOR as compared to pristine Fe-MOF-bpdc, the amount of evolved O2 being increased by about 2 times at the maximum with CoOx loading of 2 wt% as Co metal. Investigations on the wavelength dependence of visible-light-driven WOR on CoOx@Fe-MOF-bpdc revealed that the direct photo-excitation of Fe-oxo clusters within Fe-MOF-bpdc plays an important role to initiate the reaction. Furthermore, it was found that the rate of 2-propanol oxidation reaction, which is a typical two-electron oxidation reaction, was hardly affected by CoOx deposition, suggesting that CoOx acts as a unique hole trapping site and more preferentially catalyse the four-electron oxidation reactions like WOR than the two-electron oxidation reaction.

Generation of surface active sites with tailor-made structure is a promising way to enhance catalytic properties of inexpensive metal oxides, as a replacement to noble metals. In the abatement of N...

Derivatives of malachite green, a well-known triphenylmethine dye, have been adapted for third-generation photovoltaic applications as dye-sensitized solar cells (DSSC). The solar cells were developed based on a concentrated Br3−/Br− liquid electrolyte coupled to different trifluoroacetate (TFA−), triflate (TfO−), bromide (Br−) and tetrafluoroborate (BF4−) malachite green salts as dye sensitizers and mesoporous TiO2 anatase as electron collector, and their optoelectronic properties were characterized. The adsorption patterns of such salts at the TiO2 nanoparticle surface were studied by zeta (ζ) potential measurements on colloidal suspensions under neat conditions, and compared to the desorption rates of the dyes when exposed to the DSSC electrolyte. The different affinities of the ionic pairs for the oxide surface and the bulk were found crucial for the stability of the self-assembled monolayer of carboxylic acid-anchored chromophores at the surface, and for the photoconversion efficiency associated ther...

Various triflate (TfO–), tetrafluoroborate (BF4–), and perchlorate (ClO4–) salts of (E)-9-(3-(4-(diphenylamino)phenyl)allylidene)-9H-carbazol-9-ium chromophores, asymmetrical streptocyanine blue dyes, were synthesized, and their structures and photochemical and electrochemical properties were characterized. Displaying a high absorption band in the wavelength range 620–640 nm in acidified benzonitrile, the dyes provide an intense absorption at longer wavelength thanks to their oxidized π-conjugated systems. The π-electronic structure underwent twisting and bending, counteracting the electron-donating/withdrawing induction of its different substituents with a propensity to cancel its dipole moment and HOMO–LUMO charge-transfer coefficient. Zeta potential measurements of colloidal suspensions of sensitized TiO2 anatase nanoparticles outlined the difference in electric behavior of the organic ionic pairs at the surface of the nanoparticles: The noncoordinating or coordinating characters of the counterions wer...

Anchoring titania on carbon sphere forms a core–shell structure (TiO2@CS) which shows high-performance visible light response photocatalysis. In order to further improve such photocatalysis, herein acrylic acid (AA) is employed to modify the surface chemistry of CS so as to craft the interfacial structure between CS and TiO2. It was found that AA addition leads to morphology change from smooth to rough surface or to aggregates of smaller primary nanoparticles which, however, do not impede formation of the close contact core–shell structure with TiO2. Detailed analysis demonstrates a complex change in surface functional groups of CS in which the acidic OH is the major type whose quantity shows a peak maximum and a continuous increase at small and large AA addition ranges, respectively. Photocatalysis, photocurrent, and DFT calculation certificate that rather than COOH, the acidic OH, particularly, that related to sufficiently conjugated backbone carbon contributes to the formation of the interfacial structure which facilitates better visible light responsive photocatalysis. Benefiting from the improved interfacial charge separation, the visible light photoactivity reaches the highest when the quantity of the conjugated carbon-related OH becomes the maximum. An explicit charge transfer mechanism is proposed based on both experimental and theoretical calculation results.

TiO 2 -encapsulated H-ZSM photocatalysts were prepared by physical mixing of TiO 2 and zeolites. Pt was immobilized on the surface of the TiO 2 -encapsulated zeolite (H-ZSM) catalysts by a simple photochemical reduction method. Different weight ratios of both TiO 2 and Pt were hybridized with H-ZSM and the catalytic performance of the prepared catalysts was investigated for 2-propanol oxidation in liquid phase and acetaldehyde in gas phase reaction. Around 5–10 wt% TiO 2 -encapsulated H-ZSM catalysts was found to be optimal amount for the effective oxidation of the organics. Prior to light irradiation, Pt-TiO 2 -H-ZSM showed considerable amount of catalytic degradation of 2-propanol in the dark, forming acetone as an intermediate. In this study, Pt has played a major and important role on the total oxidation of 2-propanol as well as acetaldehyde. As a result, no residual organics were present in the pores of the zeolites. The catalysts could be reused more than three times without losing their catalytic activity in both phases. The Pt-TiO 2 -H-ZSM photocatalysts could overcome the problem of strong adsorption of organics in the zeolite pores (after the reaction). Thus, Pt-TiO 2 -H-ZSM can be used as a potential catalyst for both liquid and gas phase oxidation of organic pollutants.