Subsurface Carbon: A General Feature of Noble Metals

Recent Advances in Carbon Dioxide Adsorption, Activation and Hydrogenation to Methanol using Transition Metal Carbides

The inevitable emission of carbon dioxide (CO₂ ) due to the burning of a substantial amount of fossil fuels has led to serious energy and environmental challenges. Metal-based catalytic CO₂ transformations into commodity chemicals are a favorable approach in the CO₂ mitigation strategy. Among these transformations, selective hydrogenation of CO₂ to methanol is the most promising process that not only fulfils the energy demands but also re-balances the carbon cycle. The investigation of CO₂ adsorption on the surface of heterogeneous catalyst is highly important because the formation of various intermediates which determines the selectivity of product. Transition metal carbides (TMCs) have received considerable attention in recent years because of their noble metal-like reactivity, ceramic-like properties, high chemical and thermal stability. These features make them excellent catalytic materials for a variety of transformations such as CO₂ adsorption and its conversion into value-added chemicals. Herein, the catalytic properties of TMCs are summarize along with synthetic methods, CO₂ binding modes, mechanistic studies, effects of dopant on CO₂ adsorption, and carbon/metal ratio in the CO₂ hydrogenation reaction to methanol using computational as well as experimental studies. Additionally, this Review provides an outline of the challenges and opportunities for the development of potential TMCs in CO₂ hydrogenation reactions.

Cu Catalysts Doped with a Heteroatom into the Subsurface: Unraveling the Role of Subsurface Chemistry in Tuning the Catalytic Performance of C2H2 Selective Hydrogenation

Heteroatoms doped into the subsurface of transition metals play a vital role in heterogeneous catalysis via either expressing surface structures or even directly participating in the reaction. Herein, DFT calculations and microkinetic modeling are implemented to examine C₂H₂ selective hydrogenation over heteroatom (H, B, C, N, or P)-doped Cu(111) and Cu(211) subsurfaces, which are compared with pure Cu(111) and Cu(211) to unravel the role of subsurface chemistry in tuning the surface structure and further regulating catalytic performance. Our results indicate that the catalytic performance toward C₂H₂ selective hydrogenation is closely related to the type of doped subsurface heteroatom and the Cu surface coordination environment, which can be attributed to the simultaneous change of Cu surface geometric and electronic structures. Catalytic performance improvement over the heteroatom-doped Cu(111) is generally better than that over the doped Cu(211); especially, B- or N-doped Cu(111) has excellent C₂H₄ activity and selectivity and greatly inhibits green oil. For the heteroatom-doped Cu(211), better performance is only obtained on P-Cu(211), which is still lower than the B- and N-doped Cu(111). The subsurface heteroatom doping should focus on high-coordination Cu(111) instead of low-coordination Cu(211). AIMD simulations verified the thermal stability of B-Cu(111) and N-Cu(111); both were screened out to be the most suitable catalysts toward C₂H₂ hydrogenation. This work clearly unravels the role of subsurface chemistry in heterogeneous catalysis and contributes to the rational design of high-performance metal catalysts by tuning surface structures with the heteroatom into the subsurface.

Synthesis, modifications and applications of MILs Metal-organic frameworks for environmental remediation: The cutting-edge review

Ever-increasing anthropogenic activities are radically deteriorating the environment by causing severe pollution. Thus, curtailing the environmental pollution and promotion of sustainable development, are the hot issues confronted by scientists in this modern era. Metal-organic frameworks (MOFs) have been highly recognized as emerging promising materials for environmental remediation due to their versatile structure and extraordinary properties. Among them, MILs (MIL = Matérial Institute of Lavoisier) are the series of MOFs mostly known for their incredible stability, unique tailorable pore structures, and astounding versatile environmental applications. Their exclusive physiochemical properties and multifunctionality make them proficient for a wide range of pollutants removal in the exposure of versatile harsh environments, compared to other MOFs. This piece of research summarizes the state-of-the-art of development of MILs on the broad spectrum, highlighting their specificities, such as synthesis techniques, modifications and applications for environmental remediation. However, MILs wonderful properties and extraordinary applications in multiple fields, their deployment on practical and commercial-scale pollutants remediation is hindered by insufficient scientific research on underlying mechanisms and relationships. Henceforth, this review not only signifies the emerging importance of MILs for environmental applications but also indicates the urgency to maximize the scientific research for exploitation of MOFs on a practical level and promotion of green technologies for environmental remediation.

The Electrophilicity of Surface Carbon Species in the Redox Reactions of CuO-CeO2 Catalysts

Electronic metal–support interactions (EMSI) describe the electron flow between metal sites and a metal oxide support. It is generally used to follow the mechanism of redox reactions. In this study of CuO‐CeO₂ redox, an additional flow of electrons from metallic Cu to surface carbon species is observed via a combination of operando X‐ray absorption spectroscopy, synchrotron X‐ray powder diffraction, near ambient pressure near edge X‐ray absorption fine structure spectroscopy, and diffuse reflectance infrared Fourier transform spectroscopy. An electronic metal–support–carbon interaction (EMSCI) is proposed to explain the reaction pathway of CO oxidation. The EMSCI provides a complete picture of the mass and electron flow, which will help predict and improve the catalytic performance in the selective activation of CO₂, carbonate, or carbonyl species in C1 chemistry.