Facile synthesis of precious-metal single-site catalysts using organic solvents

Constructing and controlling ruthenium active phases for acetylene hydrochlorination

Ru-Based catalysts with distinct active phases from Ru0, to RuO2, RuCl3 and RuCl2N were synthesized and evaluated in acetylene hydrochlorination. RuCl2N is identified as the efficient active phase due to its co-activation of acetylene and hydrogen chloride. This discovery holds great potential to accelerate the large-scale application of Ru-based catalysts in industry.

Recent Advances in Single-Atom Electrocatalysts for Oxygen Reduction Reaction

Oxygen reduction reaction (ORR) plays significant roles in electrochemical energy storage and conversion systems as well as clean synthesis of fine chemicals. However, the ORR process shows sluggish kinetics and requires platinum-group noble metal catalysts to accelerate the reaction. The high cost, rare reservation, and unsatisfied durability significantly impede large-scale commercialization of platinum-based catalysts. Single-atom electrocatalysts (SAECs) featuring with well-defined structure, high intrinsic activity, and maximum atom efficiency have emerged as a novel field in electrocatalytic science since it is promising to substitute expensive platinum-group noble metal catalysts. However, finely fabricating SAECs with uniform and highly dense active sites, fully maximizing the utilization efficiency of active sites, and maintaining the atomically isolated sites as single-atom centers under harsh electrocatalytic conditions remain urgent challenges. In this review, we summarized recent advances of SAECs in synthesis, characterization, oxygen reduction reaction (ORR) performance, and applications in ORR-related H₂O₂ production, metal-air batteries, and low-temperature fuel cells. Relevant progress on tailoring the coordination structure of isolated metal centers by doping other metals or ligands, enriching the concentration of single-atom sites by increasing metal loadings, and engineering the porosity and electronic structure of the support by optimizing the mass and electron transport are also reviewed. Moreover, general strategies to synthesize SAECs with high metal loadings on practical scale are highlighted, the deep learning algorithm for rational design of SAECs is introduced, and theoretical understanding of active-site structures of SAECs is discussed as well. Perspectives on future directions and remaining challenges of SAECs are presented.

In situ K-edge X-ray absorption spectroscopy of the ligand environment of single-site Au/C catalysts during acetylene hydrochlorination

The replacement of HgCl₂/C with Au/C as a catalyst for acetylene hydrochlorination represents a significant reduction in the environmental impact of this industrial process. Under reaction conditions atomically dispersed cationic Au species are the catalytic active site, representing a large-scale application of heterogeneous single-site catalysts. While the metal nuclearity and oxidation state under operating conditions has been investigated in catalysts prepared from aqua regia and thiosulphate, limited studies have focused on the ligand environment surrounding the metal centre. We now report K-edge soft X-ray absorption spectroscopy of the Cl and S ligand species used to stabilise these isolated cationic Au centres in the harsh reaction conditions. We demonstrate the presence of three distinct Cl species in the materials; inorganic Cl^-, Au-Cl, and C-Cl and how these species evolve during reaction. Direct evidence of Au-S interactions is confirmed in catalysts prepared using thiosulfate precursors which show high stability towards reduction to inactive metal nanoparticles. This stability was clear during gas switching experiments, where exposure to C₂H₂ alone did not dramatically alter the Au electronic structure and consequently did not deactivate the thiosulfate catalyst.

Single atomic site catalysts: synthesis, characterization, and applications

Single atomic site catalysts (SASCs) have attracted great attention in heterogenous catalysis due to their maximized atomic utilization and unique electronic structure. This feature article summarizes the recent contributions of the authors in the synthesis, characterization, and applications of SASCs. Firstly, we disclose the tricks of our recent progress in the synthesis of SASCs, including impregnation of metal precursors on defect-rich supports, pyrolysis of polymer-encapsulated metals and isolation of contiguous atoms by alloying. Then, we show several key characterization technologies to identify the geometric and electronic structure of SASCs, and reveal the advantages and disadvantages of these characterization technologies. Finally, the applications of the SASCs in heterogenous catalysis are presented, which are classified into electrocatalysis and thermocatalysis, and the structure-function relationships are disclosed.