No abstract

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.

Efficient interfacial charge transfer is essential in graphene-based semiconductors to realize their superior photoactivity. However, little is known about the factors (for example, semiconductor morphology) governing the charge interaction. Here, it is demonstrated that the electron transfer efficacy in reduced graphene oxide-bismuth oxide (RGO/BiVO ) composite is improved as the relative exposure extent of {010}/{110} facets on BiVO increases, indicated by the greater extent of photocurrent enhancement. The dependence of charge transfer ability on the exposure degree of {010} relative to {110} is revealed to arise due to the difference in electronic structures of the graphene/BiVO {010} and graphene/BiVO {110} interfaces, as evidenced by the density functional theory calculations. The former interface is found to be metallic with higher binding energy and smaller Schottky barrier than that of the latter semiconducting interface. The facet-dependent charge interaction elucidated in this study provides new aspect for design of graphene-based semiconductor photocatalyst useful in manifold applications.

Strong metal–support interaction (SMSI) is a phenomenon commonly observed on heterogeneous catalysts. Here, direct evidence of SMSI between noble metal and 2D TiB2 supports is reported. The temperature‐induced TiB2 overlayers encapsulate the metal nanoparticles, resulting in core–shell nanostructures that are sintering‐resistant with metal loadings as high as 12.0 wt%. The TiOx‐terminated TiB2 surfaces are the active sites catalyzing the dehydrogenation of formic acid at room temperature. In contrast to the trade‐off between stability and activity in conventional SMSI, TiB2‐based SMSI promotes catalytic activity and stability simultaneously. By optimizing the thickness and coverage of the overlayer, the Pt/TiB2 catalyst displays an outstanding hydrogen productivity of 13.8 mmol g−1cat h−1 in 10.0 m aqueous solution without any additive or pH adjustment, with >99.9% selectivity toward CO2 and H2. Theoretical studies suggest that the TiB2 overlayers are stabilized on different transition metals through an interplay between covalent and electrostatic interactions. Furthermore, the computationally determined trends in metal–TiB2 interactions are fully consistent with the experimental observations regarding the extent of SMSI on different transition metals. The present research introduces a new means to create thermally stable and catalytically active metal/support interfaces for scalable chemical and energy applications.

Au nanoparticles with different sizes (10, 20, 30, and 50 nm) were synthesized using a seed-assisted approach and anchored onto Pt/TiO employing 3-mercaptopropionic acid as the organic linker. The sizes of the Au nanoparticles were controlled within a narrow range so that the size-dependent surface plasmonic resonance effect on sensitizing Pt/TiO can be thoroughly studied. We found that 20 nm Au nanoparticles (Au) gave the best performance in sensitizing Pt/TiO to generate H under visible-light illumination. Photoelectrochemical measurements indicated that Au-Pt/TiO exhibited the most efficient "hot" electrons separation among the studied catalysts, correlating well with the photocatalytic activity. The superior performance of Au-supported Pt/TiO (Au-Pt/TiO) compared with Au anchored to TiO (Au/TiO) revealed the important role of Pt as a cocatalyst for proton reduction. To elucidate how the visible-light excited hot electrons in Au nanoparticles involved in the proton-reduction reaction process, Au/TiO was irradiated by visible light (λ > 420 nm) with the presence of Pt precursor (HPtCl) in a methanol aqueous solution under deaerated condition. Energy-dispersive X-ray spectroscopy mapping analysis on the recovered sample showed that Pt ions could be reduced on the surfaces of both Au nanoparticles and TiO support. This observation indicated that the generated hot electrons on Au nanoparticles were injected into the TiO conduction band, which were then subsequently transferred to Pt nanoparticles where proton reduction proceeded. Besides, the excited hot electrons could also participate in the proton reduction on Au nanoparticles surface.

No abstract

To address an important challenge in the engineering of antioxidant nanoparticles, the present work devised a surface-to-bulk migration of oxygen vacancies in the oxygen radical-scavenging cerium-oxide nanoparticles. The study highlights the significance of surface oxygen vacancies in the intended cellular internalization and, subsequently, the radical scavenging activity of the nanoparticles inside the cells. The findings advise future development of therapeutic antioxidant nanomaterials to also include engineering of the particles for enhanced surface defects not only for the accessibility of their oxygen vacancies but also, equally important, rendering them bioavailable for cellular uptake.

Defective 3D vertical graphene (VG) with a relatively large surface area, high defect density, and increased surface electrons is synthesized via a scalable plasma enhanced chemical vapor deposition method, together with a postsynthesis Ar‐plasma treatment (VG‐Ar). Subsequently, Cu@CuxO nanoparticles are deposited onto VG‐Ar (Cu/VG‐Ar) through a galvanostatic pulsed electrodeposition method. These Cu@CuxO nanocatalyst systems exhibit a superior electrochemical CO2 reduction performance when compared to Cu‐based catalysts supported on commercial graphene paper or pristine VG without postsynthesis Ar‐plasma treatment. The Cu/VG‐Ar achieves the highest CO2 reduction Faradaic efficiency of 60.6% (83.5% of which are attributed to liquid products, i.e., formate, ethanol, and n‐propanol) with a 5.6 mA cm−2 partial current density at −1.2 V versus reversible hydrogen electrode (RHE). The improved CO2 reduction performance of Cu/VG‐Ar originates from the well‐dispersed Cu@CuxO nanoparticles deposited on the defective VG‐Ar. The intrinsic carbon defects on VG‐Ar can suppress the hydrogen evolution reaction as well as tune the interaction between VG and Cu@CuxO, thus impeding the excessive oxidation of Cu2O species deposited on VG‐Ar. The defective VG‐Ar and stabilized Cu@CuxO enhances CO2 adsorption and promotes electron transfer to the adsorbed CO2 and intermediates on the catalyst surface, thus improving the overall CO2 reduction performance.