Recent Advances in Single-Atom Catalysts

Recent Advances in Single-Atom Catalysts

Since the concept of single-atom catalysis was proposed by Academician Tao Zhang from Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Prof. Jun Li from Tsinghua University and Prof. Jingyue Liu from Arizona State University in 2011, single-atom catalysts have become a high-speed dynamic and fast-developing field in recent years. Single-atom catalysts achieve atomic scale homogeneity of catalytic sites and show the advantages of homogeneous catalysts with high atom utilization, high activity and selectivity.A In addition to this, single-atom catalysts have multiphase characteristics such as easy separation, recyclability and good stability, which combine the advantages of both homogeneous and multiphase catalysts, and are regarded as important bridges between homogeneous and multiphase catalysts. Therefore, the establishment of feasible synthesis strategies for the preparation of high-performance catalysts, in-depth understanding of the active site structure and catalytic mechanism, and the development of practical catalysts with industrial value are the important research directions for single-atom catalysts at present.

1. Adv.Mater: dynamic reconfiguration between copper monoatoms and clusters during electrocatalytic urea synthesis

The synthesis of this catalyst was carried out with an average urea yield of 52.84 mmol h-1 gcat-1 at an applied potential of -1.6 V versus RHE. XAS spectra showed the remodeling of copper monoatoms (Cu1) to clusters (Cu4) during electrolysis, and this electrochemically reconfigured Cu4 clusters are the real active sites for electrocatalytic urea. Favorable carbon and nitrogen coupling reactions and urea formation on Cu4 were verified using SR-FTIR and DFT calculations. When the applied potential is switched to an open-circuit potential, the clusters are dynamically and reversibly transformed to a single-atom configuration, which endows the catalyst with excellent structural and electrochemical stability. The related research results were published as “Dynamic Reconstitution Between Copper Single atoms and Clusters for Electrocatalytic Urea synthesis” in Advanced Materials

Associate researcher Xiao-Qiang An of Academician Jiu-Hui Qu’s team at the Center for Water Quality and Water Ecology, Tsinghua University, in collaboration with Professor Jun-Wang Tang of the Department of Chemical Engineering and Professor Limin Liu of Beihang University, has proposed a new strategy for sodium-assisted photo-induced assembly (SPA). Through the special interaction between sodium ions and gold atoms on the carrier surface to form stable pairs of atoms free from the titanium oxide surface, and at the same time driving the adjacent gold atoms to migrate and aggregate into clusters with the help of light field, the produced two-site synergistic catalysts show two orders of magnitude higher catalytic efficiency in the reaction of photolysis of water to produce hydrogen, which is a good example for the “bottom-up” construction of single-atom/gold catalysts at the atomic scale. “The catalytic efficiency of the produced two-site synergistic catalysts in hydrogen production from photolyzed water was enhanced by two orders of magnitude, which provides a new idea for the construction of single-atom/nanocluster synergistic multi-point catalysts on the atomic scale from the bottom up. The results were published in the Journal, “Sodium-Directed Photon-Induced Assembly Strategy for Preparing Multisite Catalysts with High Atomic Utilization Efficiency”. “The results were published in the Journal of the American Chemical Society.

The team of Prof. Ifan E. L. Stephens, Department of Materials, Royal School of Mines, Imperial College London, in conjunction with the team of Prof. Maria-Magdalena Titirici, Department of Chemical Engineering, describes a simple method for the preparation of porous N-catalysts through the use of Mg2+ salts as active site templates and porosity agents and another organic precursor, 2,4,6-triaminopyrimidine (TAP ) porous N-doped carbon hosts were prepared and then used for Fe coordination, resulting in the preparation of FeNC materials with record high FeNx electrochemical utilization. Unlike Fe (which forms nitrides and carbides upon pyrolysis), Mg2+ is a Lewis acidic metal cation that forms Nx groups and creates pores.TAP interacts efficiently with water molecules of hydrated Mg2+ salts and melts upon pyrolysis, resulting in effective polymerization and uniform distribution of Mg throughout the material.Fe was then ligated in a high-surface-area nitrogen-doped carbon (~ 3295 m2 g-1) in low-temperature wet impregnation to produce highly available FeNx active sites. The researchers conducted an in-depth study of the polymerization pathways and growth of the prepared materials by thermogravimetric analysis, mass spectrometry, solid-state nuclear magnetic resonance, and X-ray photoelectron spectroscopy.

The researchers confirmed by scanning transmission electron microscopy and energy dispersive X-ray that the