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The broad employment of water electrolysis for hydrogen (H₂) production is restricted by its large voltage requirement and low energy conversion efficiency because of the sluggish oxygen evolution reaction (OER). Herein, we report a strategy to replace OER with a thermodynamically more favorable reaction, the partial oxidation of formaldehyde to formate under alkaline conditions, using a Cu₃Ag₇electrocatalyst. Such a strategy not only produces more valuable anodic product than O₂but also releases H₂at the anode with a small voltage input. Density functional theory studies indicate the H₂C(OH)O intermediate from formaldehyde hydration can be better stabilized on Cu₃Ag₇than on Cu or Ag, leading to a lower C-H cleavage barrier. A two-electrode electrolyzer employing an electrocatalyst of Cu₃Ag₇(+)||Ni₃N/Ni(–) can produce H₂at both anode and cathode simultaneously with an apparent 200% Faradaic efficiency, reaching a current density of 500 mA/cm²with a cell voltage of only 0.60 V.

 

Among many biomass‐derived intermediate compounds, 5‐hydroxymethylfurfural (HMF) has been regarded as a platform chemical because it can be used to produce numerous valuable products. However, the difficulty of HMF isolation from reaction media coupled with its poor stability have significantly inhibited its large‐scale production and application. In this work, we report a single‐step process for the direct production of HMF from glucose using green chemical methods. Optimized glucose isomerization and dehydration under microwave irradiation achieved a respectable HMF yield (70 %) using a biphasic solvent mixture (water/THF), high glucose concentration (30 % w/v), catalytic amounts of AlCl₃(5 mol%) and HCl (15 mol%). The reaction can be completed within minutes at 165 °C. Overall, our microwave‐assisted strategy enables the direct conversion of commercially available glucose to the highly valuable platform chemical HMF without the use of expensive solvents or catalysts, suggesting an economically attractive approach for upgrading carbohydrates.

 

The sluggish hydrogen oxidation reaction (HOR) under alkaline conditions has hindered the commercialization of hydroxide‐exchange membrane hydrogen fuel cells. A low‐cost Ni/NiO/C catalyst with abundant Ni/NiO interfacial sites was developed as a competent HOR electrocatalyst in alkaline media. Ni/NiO/C exhibits an HOR activity one order of magnitude higher than that of its parent Ni/C counterpart. Moreover, Ni/NiO/C also shows better stability and CO tolerance than commercial Pt/C in alkaline media, which renders it a very promising HOR electrocatalyst for hydrogen fuel cell applications. Density functional theory (DFT) calculations were also performed to shed light on the enhanced HOR performance of Ni/NiO/C; the DFT results indicate that both hydrogen and hydroxide achieve optimal binding energies at the Ni/NiO interface, resulting from the balanced electronic and oxophilic effects at the Ni/NiO interface.

 

Abstract It is very attractive yet underexplored to synthesize heterocyclic moieties pertaining to biologically active molecules from biomass-based starting compounds. Herein, we report an electrocatalytic Achmatowicz reaction for the synthesis of hydropyranones from furfuryl alcohols, which can be readily produced from biomass-derived and industrially available furfural. Taking advantage of photo-induced polymerization of a bipyridyl ligand, we demonstrate the facile preparation of a heterogenized nickel electrocatalyst, which effectively drives the Achmatowicz reaction electrochemically. A suite of characterization techniques and density functional theory computations were performed to aid the understanding of the reaction mechanism. It is rationalized that the unsaturated coordination sphere of nickel sites in our electrocatalyst plays an important role at low applied potential, not only allowing the intimate interaction between the nickel center and furfuryl alcohol but also enabling the transfer of hydroxide from nickel to the bound furfuryl alcohol. 

Direct electrochemical halogenation has appeared as an appealing approach in synthesizing organic halides in which inexpensive inorganic halide sources are employed and electrical power is the sole driving force. However, the intrinsic characteristics of direct electrochemical halogenation limit its reaction scope. Herein, we report an on-site halogenation strategy utilizing halogen gas produced from halide electrolysis while the halogenation reaction takes place in a reactor spatially isolated from the electrochemical cell. Such a flexible approach is able to successfully halogenate substrates bearing oxidatively labile functionalities, which are challenging for direct electrochemical halogenation. In addition, low-polar organic solvents, redox-active metal catalysts, and variable temperature conditions, inconvenient for direct electrochemical reactions, could be readily employed for our on-site halogenation. Hence, a wide range of substrates including arenes, heteroarenes, alkenes, alkynes, and ketones all exhibit excellent halogenation yields. Moreover, the simultaneously generated H 2 at the cathode during halide electrolysis can also be utilized for on-site hydrogenation. Such a strategy of paired halogenation/hydrogenation maximizes the atom economy and energy efficiency of halide electrolysis. Taking advantage of the on-site production of halogen and H 2 gases using portable halide electrolysis but not being suffered from electrolyte separation and restricted reaction conditions, our approach of flexible halogenation coupled with hydrogenation enables green and scalable synthesis of organic halides and value-added products. 

Due to its clean and sustainable nature, solar energy has been widely recognized as a green energy source in driving a variety of reactions, ranging from small molecule activation and organic transformation to biomass valorization. Within this context, organic reactions coupled with H 2 evolution via semiconductor-based photocatalytic systems under visible light irradiation have gained increasing attention in recent years, which utilize both excited electrons and holes generated on semiconductors and produce two types of value-added products, organics and H 2 , simultaneously. Based on the nature of the organic reactions, in this review article we classify semiconductor-based photocatalytic organic transformations and H 2 evolution into three categories: (i) photocatalytic organic oxidation reactions coupled with H 2 production, including oxidative upgrading of alcohols and biomass-derived intermediate compounds; (ii) photocatalytic oxidative coupling reactions integrated with H 2 generation, such as C–C, C–N, and S–S coupling reactions; and (iii) photo-reforming reactions together with H 2 formation using organic plastics, pollutants, and biomass as the substrates. Representative heterogeneous photocatalytic systems will be highlighted. Specific emphasis will be placed on their synthesis, characterization, and photocatalytic mechanism, as well as the organic reaction scope and practical application. 

The increasing demand for green chemical products calls for the exploration of sustainable and renewable carbon resources beyond fossil-based materials, whose utilization inevitably results in environmental concerns. As such, biomass valorisation has attracted increasing attention because biomass is the most widely available and sustainable carbon source. Among the available biomass-derived platform chemicals, 5-hydroxymethylfurfural (HMF) has long been regarded as an attractive candidate for the production of numerous value-added products. Nevertheless, the poor stability, and difficult separation and purification of HMF from fructose dehydration significantly inhibit its large-scale application. Herein, we report a two-step process for the direct production of two biopolymer precursors, 2,5-furandicarboxylic acid (FDCA) and 2,5-bis(hydroxymethyl)furan (BHMF), from fructose, bypassing the isolation of HMF. FDCA and BHMF are much easier to separate and purify from the reaction mixture than HMF, and they both can replace petroleum-based counterparts in the syntheses of many industrially important polymers, ranging from polyesters to polyamides. Optimized fructose dehydration under microwave irradiation achieved a high HMF yield (83%) using a biphasic strategy. The subsequent electrocatalytic conversion of the resulting microwave reaction mixture allowed us to carry out either oxidation or reduction via readily tuning the electrochemical parameters to yield FDCA or BHMF, respectively. The integration of microwave irradiation and electrocatalysis in a flow electrolyzer enabled the direct conversion of readily available fructose to highly valuable FDCA and BHMF without the expensive and challenging step of HMF isolation, suggesting an economically attractive approach for upgrading carbohydrates.