Natural Product Glycine Betaine as an Efficient Catalyst for Transformation of CO₂ with Amines to Synthesize <i>N</i>‑Substituted Compounds

Transformation of carbon dioxide (CO₂) into value-added chemicals is of great importance, and use of natural products as a catalyst is very interesting. Herein, we used the naturally occurring glycine betaine as an efficient and renewable catalyst for the formation of a C–N bond between CO₂ and amines using PhSiH₃ as the reductant. The effects of different factors on the reaction were studied. It was demonstrated that the catalyst was very active for the reactions, and a broad range of amine substrates could be converted with satisfactory yields. Moreover, the selectivity to different <i>N</i>-substituted compounds could be controlled by the molar ratio of reactants (i.e., CO₂, amines, and PhSiH₃) and the reaction temperature. In the catalytic cycle, the carbon oxidation state of CO₂ could be reduced to +2, 0, and −2, respectively, and thus, the corresponding formamides, aminals, and methylamines were produced via successive two-electron reduction steps

Porous Hafnium Phosphonate: Novel Heterogeneous Catalyst for Conversion of Levulinic Acid and Esters into γ‑Valerolactone

Catalytic transfer hydrogenation (CTH) of levulinic acid (LA) and its esters to produce γ-valerolactone (GVL) is an important route for biomass transformation. Development of efficient and heterogeneous catalysts for the GVL production via CTH reaction of LA and its esters has attracted much attention. In this work, a new hafnium (Hf) containing organic–inorganic hybrid catalyst (Hf-ATMP) was prepared by the reaction of HfCl₄ and amino tri­(methylene phosphonic acid) and was used to catalyze the CTH reaction of LA and its esters to produce GVL using isopropanol as the hydrogen source. It was found that the prepared Hf-ATMP could catalyze the CTH reaction to provide satisfactory GVL yield, and the effects of reaction temperature, reaction time, and the amount of the catalyst on the reaction were studied in detail. Meanwhile, the Hf-ATMP could be reused at least five times without notable decrease in activity and selectivity. Systematic studies indicated that the acidity of Hf, the basicity of the phosphate groups, and the porosity of the prepared catalyst were the main reasons for the catalytic performance of Hf-ATMP in the CTH reaction of LA and its esters

Photoelectrochemical CO₂ Reduction into Syngas with the Metal/Oxide Interface

Photoelectrochemical (PEC) reduction of CO₂ with H₂O not only provides an opportunity for reducing net CO₂ emissions but also produces value-added chemical feedstocks and fuels. Syngas, a mixture of CO and H₂, is a key feedstock for the production of methanol and other commodity hydrocarbons in industry. However, it is challenging to achieve efficient and stable PEC CO₂ reduction into syngas with controlled composition owing to the difficulties associated with the chemical inertness of CO₂ and complex reaction network of CO₂ conversion. Herein, by employing a metal/oxide interface to spontaneously activate CO₂ molecule and stabilize the key reaction intermediates, we report a benchmarking solar-to-syngas efficiency of 0.87% and a high turnover number of 24 800, as well as a desirable high stability of 10 h. Moreover, the CO/H₂ ratios in the composition can be tuned in a wide range between 4:1 and 1:6 with a total unity Faradaic efficiency. On the basis of experimental measurements and theoretical calculations, we present that the metal/oxide interface provides multifunctional catalytic sites with complementary chemical properties for CO₂ activation and conversion, leading to a unique pathway that is inaccessible with the individual components. The present approach opens new opportunities to rationally develop high-performance PEC systems for selective CO₂ reduction into valuable carbon-based chemicals and fuels

Nickel–Iron Bimetal as a Cost-Effective Cocatalyst for Light-Driven Hydrogen Release from Methanol and Water

Light-driven hydrogen evolution from liquid hydrogen carriers offers an innovative solution for the realization of safe storage and transportation of hydrogen. The exploration of efficient and cost-effective cocatalysts is highly desirable for constructing an affordable light-driven catalytic architecture. In this work, nickel–iron bimetal (NiFe) is rationally designed and then supported by gallium nitride nanowires (GaN NWs)/Si for light-driven hydrogen generation from methanol aqueous solution. Under optimized conditions, the H2 evolution rate of NiFe is even comparable to noble metals, e.g., Pt, Ru. By correlative operando spectroscopy characterizations, with density functional theory calculations, it is discovered that Fe is cooperative with Ni for dramatically lowering the energy barrier of the potential-limiting step of *CHO → *CO. What is more, by coordination of photoexcited charge carriers with photothermal effect, the production of hydrogen from CH3OH/H2O is evidently improved via the evolving track of *CH3O > *CH2O/*CHO > *CO > *CO2, in concurrent H2O dissociation toward ·OH. Combined with the superior optical and electronic attributes of the GaN NWs/Si semiconductor platform, NiFe bimetal enables the achievement of a marked hydrogen activity of 61.2 mmol g–1 h–1 by the only input of light under ambient conditions. This study presents a promising strategy for hydrogen release from liquid hydrogen carriers by using earth-abundant materials under mild conditions

Toward High CO Selectivity and Oxidation Resistance Solid Oxide Electrolysis Cell with High-Entropy Alloy

Ni-based cermet materials still persist as pronounced challenges for electrocatalysts in solid oxide electrolysis cells (SOECs), due to their insufficient CO2 catalytic efficiency and inferior resistance to oxidation. In this paper, a (Fe,Co,Ni,Cu,Mo) quinary high-entropy alloy is explored as an alternative cathode material, offering enhanced performance in the co-electrolysis of H2O and CO2 for renewable syngas production. In comparison to traditional nickel-based cathodes, an assembled SOEC employing the as-designed quinary high-entropy alloy exhibits a remarkable increase in CO2 conversion capacity and significantly enhanced oxidation resistance. In addition, the electrolysis current density increases by 18%, and a stability test for more than 110 h reveals no degradation. Moreover, the stability can be maintained for up to 40 h even without any protective gas. Morphological and spectroscopic analyses, coupled with density functional theory (DFT) calculations, elucidate that the high-entropy effect facilitates surface electron redistribution, which in turn contributes to the measurable activity by reducing the energy barrier of CO2 activation. Notably, the superior resistance to oxidation primarily originates from the in situ-formed spinel phase under oxidation conditions. This study demonstrates the satisfying performance of high-entropy alloys as cathode materials in SOEC, validating their high application potential in this field