The discord between the insufficient abundance and the excellent electrocatalytic activity of Pt urgently requires its atomic-level engineering for minimal Pt dosage yet maximized electrocatalytic performance. Here we report the design of ultrasmall triphenylphosphine-stabilized Pt6 nanoclusters for electrocatalytic hydrogen oxidation reaction in alkaline solution. Benefiting from the self-optimized ligand effect and atomic-precision structure, the nanocluster electrocatalyst demonstrates a high mass activity, a high stability, and outperforms both Pt single atoms and Pt nanoparticle analogues, uncovering an unexpected size optimization principle for designing Pt electrocatalysts. Moreover, the nanocluster electrocatalyst delivers a high CO-tolerant ability that conventional Pt/C catalyst lacks. Theoretical calculations confirm that the enhanced electrocatalytic performance is attributable to the bifold effects of the triphenylphosphine ligand, which can not only tune the formation of atomically precise platinum nanoclusters, but also shift the d-band center of Pt atoms for favorable adsorption kinetics of *H, *OH, and CO. 

https://www.nature.com/articles/s41467-022-29276-7.pdf

Atomic-precision Pt6 nanoclusters for enhanced hydrogen electro-oxidation

Activation of aryl chlorides in cross-coupling reactions is a long-standing challenge in organic synthesis that is of great interest to industry. Ultrasmall (<3 nm), atomically precise nanoclusters (NCs) are considered one of the most promising catalysts due to their high surface area and unsaturated active sites. Herein, we introduce a copper nanocluster-based catalyst, [Cu61(StBu)26S6Cl6H14] (Cu61NC) that enables C-N bond-forming reactions of aryl chlorides under visible-light irradiation at room temperature. A range of N-heterocyclic nucleophiles and electronically and sterically diverse aryl/hetero chlorides react in this new Cu61NC-catalyzed process to afford the C-N coupling products in good yields. Mechanistic studies indicate that a single-electron-transfer (SET) process between the photoexcited Cu61NC complex and aryl halide enables the C-N-arylation reaction.

Visible-Light Copper Nanocluster Catalysis for the C-N Coupling of Aryl Chlorides at Room Temperature.

A large surface-to-volume ratio is one of the most intriguing characteristics of nanoclusters, which endows the nanoclusters with novel properties and applications. In this work, surface engineering with a functional DPPF ligand and Cd atom is employed on a Au38 nanocluster to obtain a Au–Cd alloy nanocluster, that is, Au27Cd1(SAdm)14(DPPF)Cl (Au27Cd1 in short, DPPF = 1,1′-bis(diphenylphosphino)ferrocene, HSAdm = 1-adamantanethiol). Various characterization techniques are used to characterize the precise formulation and atomic structure of the Au27Cd1 nanocluster. To demonstrate the influence of surface engineering on the properties of nanoclusters, the difference in optical, electrochemical and electrocatalytic activities in the oxygen reduction reaction (ORR) between Au38 and Au27Cd1, as well as the stability of Au27Cd1, is explored. The results indicate the importance of surface engineering, that is, the introduction of functional ligands and surface doping of Cd atoms contribute to the enhancement of catalytic activity. This work sheds light on the surface engineering of nanoclusters and provides a new perspective for the performance optimization of nanoclusters.

Construction of a new Au27Cd1(SAdm)14(DPPF)Cl nanocluster by surface engineering and insight into its structure–property correlation

Alkali metals are used as promoters in a broad range of catalytic reactions involving supported metal catalysts, and the origin of their promotional effects has become one of the fundamental questions in heterogeneous catalysis. However, a thorough understanding of the promotional mechanism is still unclear. Combining experiments and theory, the effects of alkali metals on the reactivity of CO2 methanation reaction over Ru/ZrO2, a crucial reaction for CO2 utilization is explored. The conventionally assumed electron enrichment of Ru is not the decisive factor for the promotion. Rather, Na promotion facilitate the adsorption and dissociation of CO on the local interfacial Ru sites of Ru/ZrO2, which is the key step of CO2 methanation process. The feasible dissociation of CO on the alkali metal promoted Ru/ZrO2 originates from the enhanced electron back-donation from the interfacial Ru sites, which leads to more than an order of magnitude increase in CO2 conversion activity. 

Unveiling the origin of alkali metal promotion in CO2 methanation over Ru/ZrO2

Long-lasting yet visible-light-driven bacterial inhibition is highly desired for environmental protection and public health maintenance. However, conventional semiconductors such as titanium dioxide (TiO2) are impotent for such antibacterial application due to their low utilization rate for visible light. Herein we report the design of a long-lasting yet visible-light-driven antibacterial agent based on marrying luminescent Au nanoclusters (Au NCs for short) to TiO2 (TiO2-NH2@Au NCs). The as-obtained TiO2-NH2@Au NC antibacterial agent not only possesses superior utilization for visible light due to the participation of Au NCs as a good photosensitizer, but also has excellent separation efficacy of photogenerated carriers, thereby efficiently enhancing the generation of reactive oxygen species (ROS) for killing bacteria. Consequently, the TiO2-NH2@Au NCs display excellent antibacterial activity with good durability against both Gram-positive and Gram-negative bacteria such as Staphylococcus aureus (99.37%) and Escherichia coli (99.92%) under visible-light irradiation (λ ≥ 400 nm). This study is interesting because it provides a paradigm change in the design of long-lasting yet visible-light-driven NC-based antibacterial agents for diversified bactericidal applications.

Marrying luminescent Au nanoclusters to TiO2 for visible-light-driven antibacterial application

Recently, the creation of new heterogeneous catalysts using the unique electronic/geometric structures of small metal nanoclusters (NCs) has received considerable attention. However, to achieve this, it is extremely important to establish methods to remove the ligands from ligand-protected metal NCs while preventing the aggregation of metal NCs. In this study, the ligand-desorption process during calcination was followed for metal-oxide-supported 2-phenylethanethiolate-protected gold (Au) 25-atom metal NCs using five experimental techniques. The results clearly demonstrate that the ligand-desorption process consists of ligand dissociation on the surface of the metal NCs, adsorption of the generated compounds on the support and desorption of the compounds from the support, and the temperatures at which these processes occurred were elucidated. Based on the obtained knowledge, we established a method to form a metal-oxide layer on the surface of Au NCs while preventing their aggregation, thereby succeeding in creating a water-splitting photocatalyst with high activity and stability.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/ange.202104911

Creation of High-Performance Heterogeneous Photocatalysts by Controlling Ligand Desorption and Particle Size of Gold Nanocluster

Efficient, robust and environmentally friendly cocatalysts for photocatalysts are important for large-scale solar hydrogen production. Herein, we demonstrate that a Rh–Zr mixed oxide is an efficient cocatalyst for hydrogen evolution. Impregnation of Zr and Rh precursors (Zr/Rh = 5 wt/wt%) formed RhZrOx cocatalyst particles on Al-doped SrTiO3, which exhibited 31× higher photocatalytic water-splitting activity than a RhOx cocatalyst. X-ray photoelectron spectroscopy proved that the dissociation of Cl− ions from preformed Rh–Cl–Zr–O solid led to formation of the active phase of RhZrOx, in which the Zr/Rh ratio was critical to high catalytic activity. Additional CoOx loading as an oxygen evolution cocatalyst further improved the activity by 120%, resulting in an apparent quantum yield of 33 (±4)% at 365 nm and a long durability of 60 h. Our discovery could help scale up photocatalytic hydrogen production.

/pdf/self-activated-rh-zr-mixed-oxide-as-a-nonhazardous-1vww7jnc7o.pdf

Self-activated Rh–Zr mixed oxide as a nonhazardous cocatalyst for photocatalytic hydrogen evolution

Hard X-ray excited optical luminescence is a unique property of materials, which makes them promising for biological imaging applications. However, the preparation of biocompatible contrast agents for hard X-ray excited optical luminescence remains a considerable challenge that has, to date, not been overcome. In this study, we investigated the luminescence properties of protein-directed Au∼20 clusters upon hard X-ray irradiation, both in solution and when embedded in films.

https://pubs.rsc.org/en/content/articlepdf/2020/ra/d0ra01935f

Ryo Takahata

Papers

Creation of High-Performance Heterogeneous Photocatalysts by Controlling Ligand Desorption and Particle Size of Gold Nanocluster

Self-activated Rh–Zr mixed oxide as a nonhazardous cocatalyst for photocatalytic hydrogen evolution

Hard X-ray excited optical luminescence from protein-directed Au∼20 clusters