Plasmon enhanced selective electronic pathways in TiO2 supported atomically ordered bimetallic Au-Cu alloys

Boosting the Photocatalysis of Plasmonic Au-Cu Nanocatalyst by AuCu-TiO2 Interface Derived from O2 Plasma Treatment

Plasmonic gold (Au) and Au-based nanocatalysts have received significant attention over the past few decades due to their unique visible light (VL) photocatalytic features for a wide variety of chemical reactions in the fields of environmental protection. However, improving their VL photocatalytic activity via a rational design is prevalently regarded as a grand challenge. Herein we boosted the VL photocatalysis of the TiO₂-supported Au-Cu nanocatalyst by applying O₂ plasma to treat this bimetallic plasmonic nanocatalyst. We found that O₂ plasma treatment led to a strong interaction between the Au and Cu species compared with conventional calcination treatment. This interaction controlled the size of plasmonic metallic nanoparticles and also contributed to the construction of AuCu-TiO₂ interfacial sites by forming AuCu alloy nanoparticles, which, thus, enabled the plasmonic Au-Cu nanocatalyst to reduce the Schottky barrier height and create numbers of highly active interfacial sites. The catalyst's characterizations and density functional theory (DFT) calculations demonstrated that boosted VL photocatalytic activity over O₂ plasma treated Au-Cu/TiO₂ nanocatalyst arose from the favorable transfer of hot electrons and a low barrier for the reaction between CO and O with the construction of large numbers of AuCu-TiO₂ interfacial sites. This work provides an efficient approach for the rational design and development of highly active plasmonic Au and Au-based nanocatalysts and deepens our understanding of their role in VL photocatalytic reactions.

Laser Ablation Nanoarchitectonics of Au-Cu Alloys Deposited on TiO2 Photocatalyst Films for Switchable Hydrogen Evolution from Formic Acid Dehydrogenation

The regulation of H₂ evolution from formic acid dehydrogenation using recyclable photocatalyst films is an essential approach for on-demand H₂ production. We have successfully generated Au-Cu nanoalloys using a laser ablation method and deposited them on TiO₂ photocatalyst films (Au _x Cu_100-x /TiO₂). The Au-Cu/TiO₂ films were employed as photocatalysts for H₂ production from formic acid dehydrogenation under light-emitting diode (LED) irradiation (365 nm). The highest H₂ evolution rate for Au₂₀Cu₈₀/TiO₂ is archived to 62,500 μmol h^-1 g^-1 per photocatalyst weight. The remarkable performance of Au₂₀Cu₈₀/TiO₂ may account for the formation of Au-rich surfaces and the effect of Au alloying that enables Cu to sustain the metallic form on its surface. The metallic Au-Cu surface on TiO₂ is vital to supply the photoexcited electrons of TiO₂ to its surface for H₂ evolution. The rate-determining step (RDS) is identified as the reaction of a surface-active species with protons. The results establish a practical preparation of metal alloy deposited on photocatalyst films using laser ablation to develop efficient photocatalysts.

Photo-assisted effective and selective reduction of CO2 to methanol on a Cu–ZnO–ZrO2 catalyst

Highly selective catalysis of CO2 hydrogenation to methanol with photo-assistance on Cu–ZnO–ZrO2, a photothermal synergistic catalyst.

Synergistic ultraviolet and visible light photo-activation enables intensified low-temperature methanol synthesis over copper/zinc oxide/alumina

Although photoexcitation has been employed to unlock the low-temperature equilibrium regimes of thermal catalysis, mechanism underlining potential interplay between electron excitations and surface chemical processes remains elusive. Here, we report an associative zinc oxide band-gap excitation and copper plasmonic excitation that can cooperatively promote methanol-production at the copper-zinc oxide interfacial perimeter of copper/zinc oxide/alumina (CZA) catalyst. Conversely, selective excitation of individual components only leads to the promotion of carbon monoxide production. Accompanied by the variation in surface copper oxidation state and local electronic structure of zinc, electrons originating from the zinc oxide excitation and copper plasmonic excitation serve to activate surface adsorbates, catalysing key elementary processes (namely formate conversion and hydrogen molecule activation), thus providing one explanation for the observed photothermal activity. These observations give valuable insights into the key elementary processes occurring on the surface of the CZA catalyst under light-heat dual activation.

Highly Efficient Performance and Conversion Pathway of Photocatalytic CH3SH Oxidation on Self-Stabilized Indirect Z-Scheme g-C3N4/I3--BiOI

A self-stabilized Z-scheme porous g-C₃N₄/I^3--containing BiOI ultrathin nanosheets (g-C₃N₄/I^3--BiOI) heterojunction photocatalyst with I₃^-/I^- redox mediator was successfully synthesized by a facile solvothermal method coupling with light illumination. The structure and optical properties of g-C₃N₄/I^3--BiOI composites were systematically characterized by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared, X-ray photoelectron spectroscopy, N₂ adsorption/desorption, UV-vis diffuse reflectance spectrum, and photoluminescence. The g-C₃N₄/I^3--BiOI composites, with a heterojunction between porous g-C₃N₄ and BiOI ultrathin nanosheets, were first applied for the photocatalytic elimination of ppm-leveled CH₃SH under light-emitting diode visible light illumination. The g-C₃N₄/I^3--BiOI heterojunction with 10% g-C₃N₄ showed a dramatically enhanced photocatalytic activity in the removal of CH₃SH compared with pure BiOI and g-C₃N₄ due to its effective interfacial charge transfer and separation. The adsorption and photocatalytic oxidation of CH₃SH over g-C₃N₄/I^3--BiOI were deeply explored by in situ diffuse reflectance infrared Fourier transform spectroscopy, and the intermediates and conversion pathways were elucidated and compared. Furthermore, on the basis of reactive species trapping, electron spin resonance and Mott-Schottky experiments, it was revealed that the responsible reactive species for catalytic CH₃SH composition were h⁺, ^•O₂^-, and ¹O₂; thus, the g-C₃N₄/I^3--BiOI heterojunction followed an indirect all-solid state Z-scheme charge-transfer mode with self-stabilized I₃^-/I^- pairs as redox mediator, which could accelerate the separation of photogenerated charge and enhance the redox reaction power of charged carriers simultaneously.

Photoinduced Glycerol Oxidation over Plasmonic Au and AuM (M = Pt, Pd and Bi) Nanoparticle-Decorated TiO₂ Photocatalysts

In this study, sol-immobilization was used to prepare gold nanoparticle (Au NP)-decorated titanium dioxide (TiO₂) photocatalysts at different Au weight % (wt. %) loading (Au_x/TiO₂, where x is the Au wt. %) and Au–M NP-decorated TiO₂ photocatalysts (Au₃M₃/TiO₂), where M is bismuth (Bi), platinum (Pt) or palladium (Pd) at 3 wt. %. The Au_x/TiO₂ photocatalysts exhibited a stronger visible light absorption than the parent TiO₂ due to the localized surface plasmon resonance effect. Increasing the Au content from 1 wt. % to 7 wt. % led to increased visible light absorption due to the increasing presence of defective structures that were capable of enhancing the photocatalytic activity of the as-prepared catalyst. The addition of Pt and Pd coupled with the Au₃/TiO₂ to form Au₃M₃/TiO₂ improved the photocatalytic activity of the Au₃/TiO₂ photocatalyst by maximizing their light-absorption property. The Au₃/TiO₂, Au₃Pt₃/TiO₂ and Au₃Pd₃/TiO₂ photocatalysts promoted the formation of glyceraldehyde from glycerol as the principle product, while Au₃Bi₃/TiO₂ facilitated glycolaldehyde formation as the major product. Among all the prepared photocatalysts, Au₃Pd₃/TiO₂ exhibited the highest photocatalytic activity with a 98.75% glycerol conversion at 24 h of reaction time.