Guangbo Chen

Defect‐Rich Ultrathin ZnAl‐Layered Double Hydroxide Nanosheets for Efficient Photoreduction of CO2 to CO with Water

Defect-rich ultrathin ZnAl-layered double hydroxide nanosheets are successfully prepared. Under UV-vis irradiation, these nanosheets are superior efficient catalysts for the photoreduction of CO2 to CO with water. The formed oxygen vacancies lead to the formation of coordinatively unsaturated Zn(+) centers within the nanosheets, responsible for the very high photocatalytic activities.

Ultrafine NiO Nanosheets Stabilized by TiO2 from Monolayer NiTi-LDH Precursors: An Active Water Oxidation Electrocatalyst

Faceted NiO nanoparticles preferentially exposing high surface energy planes demand attention due to their excellent electrocatalytic properties. However, the activity of faceted NiO nanoparticles generally remains suboptimal due to their large lateral size and thickness, which severely limits the availability of coordinatively unsaturated active reactive edge and corner sites. Here, ultrafine NiO nanosheets with a platelet size of ∼4.0 nm and thickness (∼1.1 nm) stabilized by TiO2 were successfully prepared by calcination of a monolayer layered double hydroxide precursor. The ultrafine NiO nanosheets displayed outstanding performance in electrochemical water oxidation due to a high proportion of reactive NiO {110} facets, intrinsic Ni(3+) and Ti(3+) sites, and abundant interfaces, which act synergistically to promote H2O adsorption and facilitate charge-transfer.

Oxide-Modified Nickel Photocatalysts for the Production of Hydrocarbons in Visible Light

Metallic nickel nanostructures that were partially decorated by discrete nickel oxide layers were fabricated by in situ reduction of calcinated Ni-containing layered double hydroxide nanosheets, the structure of which was confirmed by extended X-ray absorption fine structure spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. The existence of the abundant interfaces between the surface Ni oxide overlayer and metallic Ni altered the geometric/electronic structure of the Ni nanoparticles, making them apt for CO activation under light irradiation. Most importantly, the unique structure favors the C-C coupling reaction on its surface, which confers the catalyst unexpected reaction power towards higher hydrocarbons at moderate reaction conditions. This study leads to a green and sustainable approach for the photocatalytic production of highly valuable chemical fuels.

Recent Advances in the Synthesis, Characterization and Application of Zn+‐containing Heterogeneous Catalysts

Monovalent Zn+ (3d104s1) systems possess a special electronic structure that can be exploited in heterogeneous catalysis and photocatalysis, though it remains challenge to synthesize Zn+‐containing materials. By careful design, Zn+‐related species can be synthesized in zeolite and layered double hydroxide systems, which in turn exhibit excellent catalytic potential in methane, CO and CO2 activation. Furthermore, by utilizing advanced characterization tools, including electron spin resonance, X‐ray absorption fine structure and density functional theory calculations, the formation mechanism of the Zn+ species and their structure‐performance relationships can be understood. Such advanced characterization tools guide the rational design of high‐performance Zn+‐containing catalysts for efficient energy conversion.

Alumina‐Supported CoFe Alloy Catalysts Derived from Layered‐Double‐Hydroxide Nanosheets for Efficient Photothermal CO2 Hydrogenation to Hydrocarbons

A series of novel CoFe-based catalysts are successfully fabricated by hydrogen reduction of CoFeAl layered-double-hydroxide (LDH) nanosheets at 300-700 °C. The chemical composition and morphology of the reaction products (denoted herein as CoFe-x) are highly dependent on the reduction temperature (x). CO2 hydrogenation experiments are conducted on the CoFe-x catalysts under UV-vis excitation. With increasing LDH-nanosheet reduction temperature, the CoFe-x catalysts show a progressive selectivity shift from CO to CH4 , and eventually to high-value hydrocarbons (C2+ ). CoFe-650 shows remarkable selectivity toward hydrocarbons (60% CH4 , 35% C2+ ). X-ray absorption fine structure, high-resolution transmission electron microscopy, Mössbauer spectroscopy, and density functional theory calculations demonstrate that alumina-supported CoFe-alloy nanoparticles are responsible for the high selectivity of CoFe-650 for C2+ hydrocarbons, also allowing exploitation of photothermal effects. This study demonstrates a vibrant new catalyst platform for harnessing clean, abundant solar-energy to produce valuable chemicals and fuels from CO2 .

Photoreduction: Defect‐Rich Ultrathin ZnAl‐Layered Double Hydroxide Nanosheets for Efficient Photoreduction of CO2 to CO with Water (Adv. Mater. 47/2015)

Catalysts with coordinatively unsaturated Zn(d+) (d < 2) centers have recently attracted attention for the photocatalytic dehydrogenation of methane. On page 7824, T. Zhang and co-workers report that Zn(+) -Vo complexes are introduced by synthesizing ultrathin ZnAl-layer double hydroxide nanosheets, which exhibit extraordinarily high activity for the photoreduction of CO2 to CO with water.

Co-Based Catalysts Derived from Layered-Double-Hydroxide Nanosheets for the Photothermal Production of Light Olefins

Solar-driven Fischer-Tropsch synthesis represents an alternative and potentially low-cost route for the direct production of light olefins from syngas (CO and H2 ). Herein, a series of novel Co-based photothermal catalysts with different chemical compositions are successfully fabricated by H2 reduction of ZnCoAl-layered double-hydroxide nanosheets at 300-700 °C. Under UV-vis irradiation, the photothermal catalyst prepared at 450 °C demonstrates remarkable CO hydrogenation performance, affording an olefin (C2-4= ) selectivity of 36.0% and an olefin/paraffin ratio of 6.1 at a CO conversion of 15.4%. Characterization studies using X-ray absorption fine structure and high-resolution transmission electron microscopy reveal that the active catalyst comprises Co and Co3 O4 nanoparticles on a ZnO-Al2 O3 mixed metal oxide support. Density functional theory calculations further demonstrate that the oxide-decorated metallic Co nanoparticle heterostructure weakens the further hydrogenation ability of the corresponding Co, leading to the high selectivity to light olefins. This study demonstrates a novel solar-driven catalyst platform for the production of light olefins via CO hydrogenation.

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

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.