A rational approach is needed to design hydrogenation catalysts that make use of Earth-abundant elements to replace the rare elements such as ruthenium, rhodium, and palladium that are traditionally used. Here, we validate a prior mechanistic hypothesis that partially saturated amine(imine)diphosphine ligands (P-NH-N-P) activate iron to catalyze the asymmetric reduction of the polar bonds of ketones and imines to valuable enantiopure alcohols and amines, with isopropanol as the hydrogen donor, at turnover frequencies as high as 200 per second at 28°C. We present a direct synthetic approach to enantiopure ligands of this type that takes advantage of the iron(lI) ion as a template. The catalytic mechanism is elucidated by the spectroscopic detection of iron hydride and amide intermediates.

Metal oxides with their myriad compositions, structures and bonding exhibit an incredibly diverse range of properties. It is however the defects in metal oxides that endow them with a variety of functions and it is the ability to chemically tailor the type, population and distribution of defects on the surface and in the bulk of metal oxides that delivers utility in different applications. In this Tutorial Review, we discuss how metal oxides with designed defects can be synthesized and engineered, to enable heterogeneous catalytic hydrogenation of gaseous carbon dioxide to chemicals and fuels. If this approach to utilization and valorization of carbon dioxide could be developed at industrially significant rates, efficiencies and scales and made economically competitive with fossil-based chemicals and fuels, then carbon dioxide refineries envisioned in the future would be able to contribute to the reduction of greenhouse gas emissions, ameliorate climate changes, provide energy security and enable protection of the environment. This would bring the vision of a sustainable future closer to reality.

Herein we introduce a straightforward, low cost, scalable, and technologically relevant method to manufacture an all-carbon, electroactive, nitrogen-doped nanoporous-carbon/carbon-nanotube composite membrane, dubbed "HNCM/CNT". The membrane is demonstrated to function as a binder-free, high-performance gas diffusion electrode for the electrocatalytic reduction of CO to formate. The Faradaic efficiency (FE) for the production of formate is 81 %. Furthermore, the robust structural and electrochemical properties of the membrane endow it with excellent long-term stability.

No abstract

No abstract

Two-dimensional (2D) materials are of considerable interest for catalyzing the heterogeneous conversion of CO 2 to synthetic fuels. In this regard, 2D siloxene nanosheets, have escaped thorough exploration, despite being composed of earth-abundant elements. Herein we demonstrate the remarkable catalytic activity, selectivity, and stability of a nickel@siloxene nanocomposite; it is found that this promising catalytic performance is highly sensitive to the location of the nickel component, being on either the interior or the exterior of adjacent siloxene nanosheets. Control over the location of nickel is achieved by employing the terminal groups of siloxene and varying the solvent used during its nucleation and growth, which ultimately determines the distinct reaction intermediates and pathways for the catalytic CO 2 methanation. Significantly, a CO 2 methanation rate of 100 mmol g Ni −1 h −1 is achieved with over 90% selectivity when nickel resides specifically between the sheets of siloxene.

The design of photocatalysts able to reduce CO to value-added chemicals and fuels could enable a closed carbon circular economy. A common theme running through the design of photocatalysts for CO reduction is the utilization of semiconductor materials with high-energy conduction bands able to generate highly reducing electrons. Far less explored in this respect are low-energy conduction band materials such as WO. Specifically, we focus attention on the use of Pd nanocrystal decorated WO nanowires as a heretofore-unexplored photocatalyst for the hydrogenation of CO. Powder X-ray diffraction, thermogravimetric analysis, ultraviolet-visible-near infrared, and in situ X-ray photoelectron spectroscopy analytical techniques elucidate the hydrogen tungsten bronze, H WO, as the catalytically active species formed via the H spillover effect by Pd. The existence in H WO of Brønsted acid hydroxyls OH, W(V) sites, and oxygen vacancies (V) facilitate CO capture and reduction reactions. Under solar irradiation, CO reduction attains CO production rates as high as 3.0 mmol g hr with a selectivity exceeding 99%. A combination of reaction kinetic studies and in situ diffuse reflectance infrared Fourier transform spectroscopy measurements provide a valuable insight into thermochemical compared to photochemical surface reaction pathways, considered responsible for the hydrogenation of CO by Pd@H WO.

Herein we introduce as traightforward, lowc ost, scalable,a nd technologically relevant method to manufacture an all-carbon, electroactive,n itrogen-doped nanoporouscarbon/carbon-nanotube composite membrane,d ubbed "HNCM/CNT". The membrane is demonstrated to function as ab inder-free,h igh-performance gas diffusion electrode for the electrocatalytic reduction of CO 2 to formate.The Faradaic efficiency (FE) for the production of formate is 81 %. Furthermore,the robust structural and electrochemical properties of the membrane endow it with excellent long-term stability.