Single atom catalyst, which contains isolated metal atoms singly dispersed on supports, has great potential for achieving high activity and selectivity in hetero-catalysis and electrocatalysis. However, the activity and stability of single atoms and their interaction with support still remains a mystery. Here we show a stable single atomic ruthenium catalyst anchoring on the surface of cobalt iron layered double hydroxides, which possesses a strong electronic coupling between ruthenium and layered double hydroxides. With 0.45 wt.% ruthenium loading, the catalyst exhibits outstanding activity with overpotential 198 mV at the current density of 10 mA cm−2 and a small Tafel slope of 39 mV dec−1 for oxygen evolution reaction. By using operando X-ray absorption spectroscopy, it is disclosed that the isolated single atom ruthenium was kept under the oxidation states of 4+ even at high overpotential due to synergetic electron coupling, which endow exceptional electrocatalytic activity and stability simultaneously. While water splitting offers a carbon-neutral means to store energy, water oxidation is sluggish and corrosive over earth-abundant electrocatalysts. Here, authors show single ruthenium atoms over cobalt-iron layered double hydroxides to be effective and stable oxygen evolution electrocatalysts.

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Boosting oxygen evolution of single-atomic ruthenium through electronic coupling with cobalt-iron layered double hydroxides

An enormous research effort is currently being directed towards the development of efficient visible-light-driven photocatalysts for renewable energy applications including water splitting, CO2 reduction and alcohol photoreforming. Layered double hydroxide (LDH)-based photocatalysts have emerged as one of the most promising candidates to replace TiO2-based photocatalysts for these reactions, owing to their unique layered structure, compositional flexibility, controllable particle size, low manufacturing cost and ease of synthesis. By introducing defects into LDH materials through the control of their size to the nanoscale, the atomic structure, surface defect concentration, and electronic and optical characteristics of LDH materials can be strategically engineered for particular applications. Furthermore, through the use of advanced characterization techniques such as X-ray absorption fine structure, positron annihilation spectrometry, X-ray photoelectron spectroscopy, electron spin resonance, density-functional theory calculations, and photocatalytic tests, structure-activity relationships can be established and used in the rational design of high-performance LDH-based photocatalysts for efficient solar energy capture. LDHs thus represent a versatile platform for semiconductor photocatalyst development with application potential across the energy sector.

Layered Double Hydroxide Nanostructured Photocatalysts for Renewable Energy Production

The discovery of improved chemical processes for CO and CO2 hydrogenation to valuable hydrocarbon fuels and alcohols is of paramount importance for the chemical industry. Such technologies have the potential to reduce anthropogenic CO2 emissions by adding value to a waste stream, whilst also reducing our consumption of fossil fuels. Current thermal catalytic technologies available for CO and CO2 hydrogenation are demanding in terms of energy input. Various alternative technologies are now being developed for COx hydrogenation, with solar-driven processes over two-dimensional (2D) and 2D-related composite materials being particularly attractive due to the abundance of solar energy on Earth and also the high selectivity of defect-engineered 2D materials towards specific valuable products under very mild reaction conditions. This review showcases recent advances in the solar-driven COx reduction to hydrocarbons over 2D-based materials. Optimization of 2D catalyst performance demands interdisciplinary research that embraces catalyst electronic structure manipulation and morphology control, surface/interface engineering, reactor engineering and density functional theory modelling studies. Through improved understanding of the structure–performance relationships in 2D-related catalysts which is achievable through the application of modern in situ characterization techniques, practical photo/photothermal/photoelectrochemical technologies for CO and CO2 reduction to high-valuable products such as olefins could be realized in the not-too-distant future.

Two-dimensional-related catalytic materials for solar-driven conversion of COx into valuable chemical feedstocks.

Layered Double Hydroxide-Based Catalysts: Recent Advances in Preparation, Structure, and Applications

Triazine-based covalent organic polymers (COPs) constructed from triazine or nitrile containing precursors via covalent bonding are becoming an important sub-class of porous organic framework materials for a range of applications. In particular, these materials have been proposed as a new catalyst or support material for a variety of liquid phase organic transformation reactions owing to their tunable porous structures with high surface area, high nitrogen contents, high stability in both organic and aqueous media, and relatively easy synthesis. This review article summarizes the current research activities devoted to the synthesis and characterization of new triazine-based COP materials, and their applications for heterogeneous catalysis aiming at fine chemicals synthesis are presented with critical comments.

Triazine-based covalent organic polymers: design, synthesis and applications in heterogeneous catalysis

Oxidation and hydrogenation catalysis plays a crucial role in the current chemical industry for the production of key chemicals and intermediates. Because of their easy separation and recyclability, supported catalysts are widely used in these two processes. Layered double hydroxides (LDHs) with the advantages of unique structure, composition diversity, high stability, ease of preparation and low cost have shown great potential in the design and synthesis of novel supported catalysts. This review summarizes the recent progress in supported catalysts by using LDHs as supports/precursors for catalytic oxidation and hydrogenation. Particularly, partial hydrogenation of acetylene, hydrogenation of dimethyl terephthalate, methanation, epoxidation of olefins, elimination of NOx and SOx emissions, and selective oxidation of biomass have been chosen as representative reactions in the petrochemical, fine chemicals, environmental protection and clean energy fields to highlight the potential application and the general functionality of LDH-based catalysts in catalytic oxidation and hydrogenation. Finally, we concisely discuss some of the scientific challenges and opportunities of supported catalysts based on LDH materials.

Supported catalysts based on layered double hydroxides for catalytic oxidation and hydrogenation: general functionality and promising application prospects

Supported Catalysts Based on Layered Double Hydroxides for Catalytic Oxidation and Hydrogenation: General Functionality and Promising Application Prospects

The invention provides a delaminated hydrotalcite nano-sheet based composite catalyst and a preparation method therefor. The preparation method for the catalyst comprises the steps of introducing cationic active ingredients into a hydrotalcite laminate to form a precursor with a layered structure, then, carrying out swelling to enable the laminate to be delaminated into 1 to 10 layers, carrying out compounding on obtained hydrotalcite nano-sheets and a support with a special surface structure or electron features, and carrying out washing and drying, thereby obtaining the M1M2-ELDH/S catalyst, wherein M1 represents a divalent metal cation for forming a hydrotalcite structure, M2 represents a trivalent metal cation for forming the hydrotalcite structure, ELDH represents a delaminated hydrotalcite nano-sheet, and S represents the support. The catalyst has the characteristics that the variety and ratio of the active ingredients are adjustable; after the laminate is delaminated into 1 to 10 layers, an active center is exposed to the maximum, and the stability and cycle use performance of the catalyst can be improved after the active center is compounded with the support; and the hydrotalcite laminate and the support with the special surface structure and the electron features generate an interaction, so that the activity and selectivity of the catalyst are further improved.

Delaminated hydrotalcite nano-sheet based composite catalyst and preparation method therefor

The invention provides a high-dispersion supported ruthenium dioxide catalyst and a preparing method thereof. The preparing method comprises the steps that a precious metal polymeric precursor solution and a soluble salt solution composing the +2 and +3 valence metal ions of hydrotalcite are mixed, nucleating and growing are carried out in an alkali solution environment provided by a precipitating agent, and the RuO2/MAl-LDH catalyst is obtained through crystallization, washing, drying and further retreatment. According to the catalyst, the precious metal Ru serves as the active ingredient and is supported on the surface of hydrotalcite MAl-LDH as a supporter, and the supported RuO2 catalyst uniform in dispersion and size is formed; the supporting amount of the active ingredient Ru is within the range of 0.5-10%, formed RuO2 nanometer particles are highly dispersed on the surface of the supporter, the particle size of the RuO2 nanometer particles ranges from 1 nm to 5 nm, and the RuO2 nanometer particles are spherical or semispherical. The transformation frequency TOF of the catalyst is remarkably higher than that of a Ru-based catalyst reported in documents in alcohol selective oxidation reactions.

Feng Junting

Papers

Supported catalysts based on layered double hydroxides for catalytic oxidation and hydrogenation: general functionality and promising application prospects

Supported Catalysts Based on Layered Double Hydroxides for Catalytic Oxidation and Hydrogenation: General Functionality and Promising Application Prospects

Delaminated hydrotalcite nano-sheet based composite catalyst and preparation method therefor

High-dispersion supported ruthenium dioxide catalyst and preparing method thereof