RESUMO
The industrial manufacture of epichlorohydrin (ECH) often suffers from excessive corrosive chlorine and multistep processes. Here, we report a one-pot membrane-free Br radical-mediated ECH electrosynthesis. Bromine radicals electro-oxidized from Br- ions initiate the reaction and then eliminate HBr from bromohydrin to give ECH and release Br- ions for reuse. A high energy barrier for *OH oxidation and isolated Br adsorption sites enables NiCo2O4 to suppress the competitive oxygen and bromine evolution reactions. The high-curvature nanotips with an increased electric field concentrate Br- and OH- ions to accelerate ECH electrosynthesis. This strategy delivers ECH with a Faradaic efficiency of 47% and a reaction rate of 1.4 mol h-1 gcat-1 at a high current density of 100 mA cm-2, exceeding the profitable target from the techno-economic analysis. Economically profitable electrosynthesis, methodological universality, and the extended synthesis of epoxide-drug blocks highlight their promising potential.
RESUMO
Electrocatalytic reduction of CO2 by metal-organic frameworks (MOFs) has been widely investigated, but insufficient conductivity limits application. Herein, a porous 3D In-MOF {(Me2 NH2 )[In(BCP)]â 2 DMF}n (V11) with good stability was constructed with two types of channels (1.6 and 1.2â nm diameter). V11 exhibits moderate catalytic activity in CO2 electroreduction with 76.0 % of Faradaic efficiency for formate (FEHCOO- ). Methylene blue molecules of suitable size and pyrolysis temperature were introduced and transformed into carbon particles (CPs) after calcination. The performance of the obtained CPs@V11 is significantly improved both in FEHCOO- (from 76.0 % to 90.1 %) and current density (2.2 times). Control experiments show that introduced CPs serve as accelerant to promote the charges and mass transfer in framework, and benefit to sufficiently expose active sites. This strategy can also work on other In-MOFs, demonstrating the universality of this method for electroreduction of CO2 .
RESUMO
Fossil fuel-driven thermochemical hydrogenation and oxidation using high-pressure H2 and O2 are still popular but energy-intensive CO2-emitting processes. At present, developing renewable energy-powered electrochemical technologies, especially those using clean, safe and easy-to-handle reducing agents and oxidants for organic hydrogenation and oxidation reactions, is urgently needed. Water is an ideal carrier of hydrogen and oxygen. Electrochemistry provides a powerful route to drive water splitting under ambient conditions. Thus, electrochemical hydrogenation and oxidation transformations involving water as the hydrogen source and oxidant, respectively, have been developed to be mild and efficient tools to synthesize organic hydrogenated and oxidized products. In this Review, we highlight the advances in water-participating electrochemical hydrogenation and oxidation reactions of representative organic molecules. Typical electrode materials, performance metrics and key characterization techniques are firstly introduced. General electrocatalyst design principles and controlling the microenvironment for promoting hydrogenation and oxygenation reactions involving water are summarized. Furthermore, paired hydrogenation and oxidation reactions are briefly introduced before finally discussing the challenges and future opportunities of this research field.
RESUMO
Electrocatalytic semihydrogenation of acetylene (C2H2) provides a facile and petroleum-independent strategy for ethylene (C2H4) production. However, the reliance on the preseparation and concentration of raw coal-derived C2H2 hinders its economic potential. Here, a concave surface is predicted to be beneficial for enriching C2H2 and optimizing its mass transfer kinetics, thus leading to a high partial pressure of C2H2 around active sites for the direct conversion of raw coal-derived C2H2. Then, a porous concave carbon-supported Cu nanoparticle (Cu-PCC) electrode is designed to enrich the C2H2 gas around the Cu sites. As a result, the as-prepared electrode enables a 91.7% C2H4 Faradaic efficiency and a 56.31% C2H2 single-pass conversion under a simulated raw coal-derived C2H2 atmosphere (~15%) at a partial current density of 0.42 A cm-2, greatly outperforming its counterpart without concave surface supports. The strengthened intermolecular π conjugation caused by the increased C2H2 coverage is revealed to result in the delocalization of π electrons in C2H2, consequently promoting C2H2 activation, suppressing hydrogen evolution competition and enhancing C2H4 selectivity.
RESUMO
The traditional synthesis of α,α-dichloroketones usually requires corrosive chlorine, harsh reaction conditions, or excessive electrolytes. Here, we report an electrooxidation strategy of ethynylbenzenes to α,α-dichloroketones by directly utilizing seawater as the chlorine source and electrolyte solution without an additional supporting electrolyte. High-curvature NiCo2O4 nanocones are designed to inhibit competitive O2 and Cl2 evolution reactions and concentrate Cl- and OH- ions, accelerating α,α-dichloroketone electrosynthesis. NiCo2O4 nanocones produce 81% yield, 61% Faradaic efficiency, and 44.2 mmol gcat.-1 h-1 yield rate of α,α-dichloroketones, outperforming NiCo2O4 nanosheets. A Cl⢠radical triggered Cl⢠and OH⢠radical addition mechanism is revealed by a variety of radical-trapping and control experiments. The feasibility of a solar-powered electrosynthesis system, methodological universality, and extended synthesis of α,α-dichloroketone-drug blocks confirm its practical potential. This work may provide a sustainable solution to the electrocatalytic synthesis of α,α-dichloroketones via the utilization of seawater resources.
RESUMO
Cyclohexanone oxime, an important nylon-6 precursor, is conventionally synthesized through cyclohexanone-hydroxylamine (NH2OH) and cyclohexanone ammoxidation methodologies. These strategies require complicated procedures, high temperatures, noble metal catalysts, and toxic SO2 or H2O2 usage. Here, we report a one-step electrochemical strategy to synthesize cyclohexanone oxime from nitrite (NO2-) and cyclohexanone under ambient conditions using a low-cost Cu-S catalyst, avoiding complex procedures, noble metal catalysts and H2SO4/H2O2 usage. This strategy produces 92% yield and 99% selectivity of cyclohexanone oxime, comparable to the industrial route. The reaction undergoes a NO2- â NH2OHâoxime reaction pathway. This electrocatalytic strategy is suitable for the production of other oximes, highlighting the methodology universality. The amplified electrolysis experiment and techno-economic analysis confirm its practical potential. This study opens a mild, economical, and sustainable way for the alternative production of cyclohexanone oxime.
RESUMO
A rare earth element doping strategy is reported to boost the activity and enhance the stability of MnO2 for selective formamide production through electrocatalytic oxidation coupling (EOC) of methanol and ammonia. MnO2 doped with 1% Pr was selected as the best candidate with an optimized formamide yield of 211.32 µmol cm-2 h-1, a Faradaic efficiency of 22.63%, and a stability of more than 50 h. The easier formation of Mn6+ species and the lower dissolution rate of Mn species over Pr-doped MnO2 revealed by in situ Raman spectra were responsible for the boosted formamide production and enhanced stability. In addition, a two-electrode flow electrolyzer was developed to integrate EOC with C2H2 semihydrogenation for simultaneously producing value-added products in both the anode and cathode.