UV-induced reactions of Mg 2+ -doped anatase nanocrystals with exposed {0 0 1} facets: An EPR study

In Situ Generation of H2O2 over MoOx Decorated on Cu2O@CuO Core-Shell Particle Nanoarchitectonics for Boosting Photocatalytic Oxidative Desulfurization

Photocatalytic oxidation desulfurization (PODS) has emerged as a promising, ecofriendly alternative to traditional, energy-intensive fuel desulfurization methods. Nevertheless, its progress is still hindered due to the slow sulfide oxidation kinetics in the current catalytic systems. Herein, we present a MoOx decorated on a Cu2O@CuO core-shell catalyst, which enables a new, efficient PODS pathway by in situ generation of hydrogen peroxide (H2O2) with saturated moist air as the oxidant source. The photocatalyst delivers remarkable specific activity in oxidizing dibenzothiophene (DBT), achieving a superior rate of 7.8 mmol g-1 h-1, while maintaining a consistent performance across consecutive reuses. Experimental investigations reveal that H2O2 is produced through the two-electron oxygen reduction reaction (ORR), and both H2O2 and the hydroxyl radicals (•OH) generated from it act as the primary reactive species responsible for sulfide oxidation. Importantly, our catalyst accomplishes complete PODS of real diesel fuel, underscoring an appealing industrial prospect for our photocatalyst.

Characterization Methodology and Activity Evaluation of Solar-Driven Catalysts for Environmental Remediation

Solar-driven photocatalysis mediated by semiconductors has been rapidly developed as a green and sustainable technology for environmental remediation. Continuous efforts have been devoted to novel semiconducting photocatalysts to boost the efficiency of the photocatalytic system. However, controversy has widely existed in materials characterization and photocatalytic activity evaluation. This review overviews the recent advances in characterization methodology and photocatalytic activity evaluation of solar-driven catalysts (SDCs) for environmental remediation. After a general and brief introduction of different SDCs, the compositional, structural, and optical characterizations of SDCs are summarized. Moreover, the characterization methods and challenges in the doped and coupled SDCs are discussed. Finally, the challenges in the evaluation of current evaluation methods for the photocatalytic activity of SDCs are highlighted.

Mn-vacancy birnessite for photo-assisted elimination of formaldehyde at ambient condition

Visible light-assisted catalysis has recently attracted considerable attention because it is efficient, cost effective, and does not cause indoor air pollution. Several birnessite-type MnO₂ catalysts with different numbers of manganese vacancies (MVs) were synthesized in this study and used for photo-assisted catalytic oxidation of HCHO. Under visible light irradiation, MVs act as trapping centers to accelerate electrons transport and produce abundant reactive radicals to boost the activation of molecular oxygen, thereby improving the catalytic HCHO oxidation. The birnessite with the highest number of MVs exhibits remarkable oxidation activity with 80 ppm of HCHO (42% HCHO conversion was attained at ambient temperature) and a corresponding gas hourly space velocity (GHSV) of 60 L/(g·h) in a dynamic experiment. Moreover, it mineralizes 80 ppm of HCHO within 160 min in a static experiment, whereas it only takes 90 min under the same conditions with the visible light irradiation. The activity factor of birnessite with the highest MV content under visible light irradiation is 2.2 times that observed under dark conditions. Overall, this study elucidates the photothermal catalytic oxidation of HCHO, and concludes that the birnessite comprising MVs is a promising material for air purification applications.

Ce ion surface-modified TiO2 aerogel powders: a comprehensive study of their excellent photocatalytic efficiency in organic pollutant removal

The surface modification of TiO₂ aerogel powders by cerium ions has led to enhanced photoinduced properties.

Facet-Dependent Electrical, Photocatalytic, and Optical Properties of Semiconductor Crystals and Their Implications for Applications

Recent studies on the electrical conductivity and photocatalytic activity properties of semiconductor nanocrystals such as Cu₂O, Ag₂O, TiO₂, PbS, and Ag₃PO₄ exposing well-defined surfaces have revealed strong facet effects. For example, the electrical conductivity of Cu₂O crystals can vary from highly conductive to nonconductive, and they can be highly photocatalytically active or inactive depending on the exposed faces. The crystal surfaces can even tune their light absorption wavelengths. Our understanding is that the emergence of these unusual phenomena can be explained in terms of the presence of an ultrathin surface layer having different band structures and degrees of band bending for different surfaces, which affects charge transport and photons into and out of the crystals. This review uses primarily results from our research on this frontier area of semiconductor properties to illustrate the existence of semiconductor facet effects. A simple adjustment to normal semiconductor band diagram allows good understanding of the observed phenomena. Recognizing that facet-dependent behaviors are intrinsic semiconductor properties, we should pay attention to their influence in the explanation of the measured photocatalytic properties, and consider ways to enhance photocatalytic efficiency or design electrical components utilizing the facet effects. There should be many opportunities to advance applications of semiconductor nanocrystals and nanostructures with continued research on the facet-dependent properties of various semiconductor materials.

Ligand-triggered electrostatic self-assembly of CdS nanosheet/Au nanocrystal nanocomposites for versatile photocatalytic redox applications

A facile and efficient ligand-triggered electrostatic self-assembly strategy has been developed to fabricate a series of Au/CdS nanosheet (Ns) (Au-CdS Ns) nanocomposites with varied weight addition ratios of Au nanoparticles (NPs) by judiciously utilizing the intrinsic surface charge properties of assembly units, through which uniform dispersion and controllable deposition of Au NPs on the CdS Ns were achieved. Versatile probe reactions including photocatalytic oxidation of an organic dye pollutant, selective photocatalytic reduction of aromatic nitro compounds and photocatalytic hydrogen production reactions under visible light irradiation and ambient conditions were used to systematically evaluate the photoredox performances of the as-assembled well-defined Au-CdS Ns nanocomposites. It was unveiled that the photoactivities of Au-CdS Ns nanocomposites strongly depend on the weight addition ratio of Au NPs and the addition of an excess amount of Au NPs is detrimental to the separation of photogenerated charge carriers from CdS Ns. With the optimum addition amount of Au NPs (1 wt%), it was found that spontaneous assembly of Au NPs on the CdS Ns remarkably prolonged the lifetime of the photogenerated charge carriers from CdS Ns under visible light irradiation, thus resulting in significantly enhanced photocatalytic redox activities of Au-CdS Ns nanocomposites compared with those of CdS Ns. The crucial role of Au NPs in the photoredox reactions as efficient electron traps rather than plasmonic sensitizers was determined. Moreover, predominant active species responsible for the photocatalytic process were unambiguously determined and a possible photocatalytic mechanism was elucidated. It is anticipated that our work could open up a new avenue to rationally prepare various 2D semiconductors-metal nanocomposites by utilizing such a simple and efficient self-assembly strategy for extensive photocatalytic applications in a myriad of fields.

Synthesis of (Ag,F)-modified anatase TiO2 nanosheets and their enhanced photocatalytic activity

The strong interactions between Ag nanoparticles and TiO₂ nanosheets can improve the photocatalytic activity of TiO₂ nanosheets.