Enhancing the Electrocatalytic Hydrogenation of Furfural via Anion-Induced Molecular Activation and Adsorption.

The electrocatalytic hydrogenation (ECH) of furfural (FF) to furfuryl alcohol, which does not require additional hydrogen or high pressure, is a green and promising production route. In this study, we explore the effects of anions on FF ECH in two buffer electrolytes (KHCO3 and phosphate-buffered saline [PBS]). Anions influence the yield of furfuryl alcohol through molecular activation and adsorption. Molecular dynamics simulations show that bicarbonate is present in the first shell layer of the FF molecule and induces strong hydrogen bonding interactions. In contrast, hydrogen phosphate is present only in the second shell layer, resulting in weak hydrogen bonding interactions. Owing to the interfacial anions and hydrogen bonding, FF molecules exhibit strong flat adsorption on the electrode surface in the KHCO3 solution, while weak adsorption is observed in the PBS solution, as confirmed by operando synchrotron-radiation Fourier-transform infrared spectroscopy and in situ Raman spectroscopy. Density-functional theory calculations reveal that the overall anionic hydrogen bonding network promotes the activation of the carbonyl group in the FF molecule in KHCO3, whereas electrophilic activity is inhibited in PBS. Consequently, FF ECH demonstrates much faster kinetics in KHCO3, while it exhibits sluggish ECH kinetics and a severe hydrogen evolution reaction in PBS. This work introduces a new strategy to optimize the catalytic process through the modulation of the microenvironment.

Catalyst Selection over an Electrochemical Reductive Coupling Reaction toward Direct Electrosynthesis of Oxime from NOx and Aldehyde.

Aqueous electrochemical coupling reactions, which enable the green synthesis of complex organic compounds, will be a crucial tool in synthetic chemistry. However, a lack of informed approaches for screening suitable catalysts is a major obstacle to its development. Here, we propose a pioneering electrochemical reductive coupling reaction toward direct electrosynthesis of oxime from NOx and aldehyde. Through integrating experimental and theoretical methods, we screen out the optimal catalyst, i.e., metal Fe catalyst, that facilitates the enrichment and C-N coupling of key reaction intermediates, all leading to high yields (e.g., ∼99% yield of benzaldoxime) for the direct electrosynthesis of oxime over Fe. With a divided flow reactor, we achieve a high benzaldoxime production of 22.8 g h-1 gcat-1 in ∼94% isolated yield. This work not only paves the way to the industrial mass production of oxime via electrosynthesis but also offers references for the catalyst selection of other electrochemical coupling reactions.

Integrated Tandem Electrochemical-chemical-electrochemical Coupling of Biomass and Nitrate to Sustainable Alanine.

Alanine is widely employed for synthesizing polymers, pharmaceuticals, and agrochemicals. Electrocatalytic coupling of biomass molecules and waste nitrate is attractive for the nitrate removal and alanine production under ambient conditions. However, the reaction efficiency is relatively low due to the activation of the stable substrates, and the coupling of two reactive intermediates remains challenging. Herein, we realize the integrated tandem electrochemical-chemical-electochemical synthesis of alanine from the biomass-derived pyruvic acid (PA) and waste nitrate (NO3 - ) catalyzed by PdCu nano-bead-wires (PdCu NBWs). The overall reaction pathway is demonstrated as a multiple-step catalytic cascade process via coupling the reactive intermediates NH2 OH and PA on the catalyst surface. Interestingly, in this integrated tandem electrochemical-chemical-electrochemical catalytic cascade process, Cu facilitates the electrochemical reduction of nitrate to NH2 OH intermediates, which chemically couple with PA to form the pyruvic oxime, and Pd promotes the electrochemical reduction of pyruvic oxime to the desirable alanine. This work provides a green strategy to convert waste NO3 - to wealth and enriches the substrate scope of renewable biomass feedstocks to produce high-value amino acids.

Electrocatalytic Synthesis of Nylon-6 Precursor at Almost 100 % Yield.

Synthesis of cyclohexanone oxime via the cyclohexanone-hydroxylamine process is widespread in the caprolactam industry, which is an upstream industry for nylon-6 production. However, there are two shortcomings in this process, harsh reaction conditions and the potential danger posed by explosive hydroxylamine. In this study, we presented a direct electrosynthesis of cyclohexanone oxime using nitrogen oxides and cyclohexanone, which eliminated the usage of hydroxylamine and demonstrated a green production of caprolactam. With the Fe electrocatalysts, a production rate of 55.9 g h-1 gcat -1 can be achieved in a flow cell with almost 100 % yield of cyclohexanone oxime. The high efficiency was attributed to their ability of accumulating adsorbed hydroxylamine and cyclohexanone. This study provides a theoretical basis for electrocatalyst design for C-N coupling reactions and illuminates the tantalizing possibility to upgrade the caprolactam industry towards safety and sustainability.

Anodic Cross-Coupling of Biomass Platform Chemicals to Sustainable Biojet Fuel Precursors.

Electrocatalytic conversion of biomass platform chemicals to jet fuel precursors is a promising approach to alleviate the energy crisis caused by the excessive exploitation and consumption of non-renewable fossil fuels. However, an aqueous electrolyte has been rarely studied. In this study, we demonstrate an anodic electrocatalysis route for producing jet fuel precursors from biomass platform chemicals on Ni-based electrocatalysts in an aqueous electrolyte at room temperature and atmosphere pressure. The desired product exhibited high selectivity for the jet fuel precursor (95.4%) and an excellent coulombic efficiency of 210%. A series of in situ characterizations demonstrated that Ni2+ species were the active sites for the coupling process. In addition, the coupling reaction could be achieved by generating radical cations and inhibiting the side reaction. First, the electrochemical process could activate the furfural (FF) molecule and generate radical cations, resulting in an average of 2.0 times chain propagation. The levulinic acid (LA) molecules played a vital role in the coupling reaction. The adsorption strength of LA on Ni3N was higher than that of FF, which could inhibit the side reaction (the oxidation of FF) and achieve high selectivity. Meanwhile, the LA molecules were adsorbed on the Ni3N surface and then disrupted the formation of Ni3+ species, thus favoring the coupling reaction. This work demonstrates an efficient route to produce jet fuel precursors directly from biomass platform chemicals and provides a comprehensive understanding of the anodic coupling process.

Salting-Out Aldehyde from the Electrooxidation of Alcohols with 100 % Selectivity.

Selective electrocatalytic oxidation of alcohols to value-added aldehydes has attracted increasing attention. However, due to its higher reactivity than alcohol, the aldehyde is easily over-oxidized to acid in alkaline electrolytes. Herein we realize the selective electrooxidation of alcohol to aldehyde on NiO by tuning the local microenvironment to salt out the aldehyde from the reaction system. The origin of the high selectivity was found to be the inhibition of the hydration of aldehydes, which is the result of the decreased alkalinity and the increased cation and substrate concentration. This strategy could salt out the aldehyde at the gas|electrolyte interface from the electrooxidation of alcohol with 100 % selectivity and be easily extended to other selective oxidation reactions, such as 5-hydroxymethyl furfural (HMF) to 2,5-furandicarboxaldehyde (DFF) and amine to an imine.

Electrochemical synthesis of 1,2,4-oxadiazoles from amidoximes through dehydrogenative cyclization.

A convenient and efficient method for the generation of the iminoxy radical through anodic oxidation was developed for the synthesis of 3,5-disubstituted 1,2,4-oxadiazoles from N-benzyl amidoximes. The transformation proceeds through 1.5-Hydrogen Atom Transfer (1,5-HAT) and intramolecular cyclization. The process features simple operation, mild conditions, broad substrate scope and high functional group compatibility, and provides a facile and practical way for the preparation of 1,2,4-oxadiazoles.

Unveiling the Electrooxidation of Urea: Intramolecular Coupling of the N-N Bond.

The nitrogenous nucleophile electrooxidation reaction (NOR) plays a vital role in the degradation and transformation of available nitrogen. Focusing on the NOR mediated by the ß-Ni(OH)2 electrode, we decipher the transformation mechanism of the nitrogenous nucleophile. For the two-step NOR, proton-coupled electron transfer (PCET) is the bridge between electrocatalytic dehydrogenation from ß-Ni(OH)2 to ß-Ni(OH)O, and the spontaneous nucleophile dehydrogenative oxidation reaction. This theory can give a good explanation for hydrazine and primary amine oxidation reactions, but is insufficient for the urea oxidation reaction (UOR). Through operando tracing of bond rupture and formation processes during the UOR, as well as theoretical calculations, we propose a possible UOR mechanism whereby intramolecular coupling of the N-N bond, accompanied by PCET, hydration and rearrangement processes, results in high performance and ca. 100 % N2 selectivity. These discoveries clarify the evolution of nitrogenous molecules during the NOR, and they elucidate fundamental aspects of electrocatalysis involving nitrogen-containing species.

Pulse potential mediated selectivity for the electrocatalytic oxidation of glycerol to glyceric acid.

Preventing the deactivation of noble metal-based catalysts due to self-oxidation and poisonous adsorption is a significant challenge in organic electro-oxidation. In this study, we employ a pulsed potential electrolysis strategy for the selective electrocatalytic oxidation of glycerol to glyceric acid over a Pt-based catalyst. In situ Fourier-transform infrared spectroscopy, quasi-in situ X-ray photoelectron spectroscopy, and finite element simulations reveal that the pulsed potential could tailor the catalyst's oxidation and surface micro-environment. This prevents the overaccumulation of poisoning intermediate species and frees up active sites for the re-adsorption of OH adsorbate and glycerol. The pulsed potential electrolysis strategy results in a higher glyceric acid selectivity (81.8%) than constant-potential electrocatalysis with 0.7 VRHE (37.8%). This work offers an efficient strategy to mitigate the deactivation of noble metal-based electrocatalysts.

Combining anodic alcohol oxidative coupling for C-C bond formation with cathodic ammonia production.

Electrocatalytic oxidation of alcohols using heterogeneous catalysts is a promising aqueous, energy-efficient and environmentally friendly approach, especially for coupling different alcohols to prolong the carbon chain via co-oxidation. Precisely regulating critical steps to tailor electrode materials and electrolyte composition is key to selectively coupling alcohols for targeted synthesis. However, selectively coupling different alcohols remains challenging due to the lack of effective catalyst and electrolyte design promoting specific pathways. Herein, we demonstrate a paired electrolysis strategy for combining anodic oxidative coupling of ethanol (EtOH) and benzyl alcohol (PhCH2OH) to synthesize cinnamaldehyde (CAL) and cathodic ammonia production. The strategies involve: (i) utilizing the salt-out effect to balance selective oxidation and coupling rates; (ii) developing platinum-loaded nickel hydroxide electrocatalysts to accelerate intermediate coupling kinetics; (iii) introducing thermodynamically favorable nitrate reduction at the cathode to improve coupling selectivity by avoiding hydrogenation of products while generating valuable ammonia instead of hydrogen. We achieved 85% coupling selectivity and 278 µmol/h NH3 productive rate at 100 mA/cm2 with a low energy input (∼1.63 V). The membrane-free, low energy, scalable approach with a wide substrate scope highlights promising applications of this methodology. This work advances heterogeneous electrocatalytic synthesis through rational design principles that integrate anodic oxidative coupling with cathodic nitrate reduction reactions, having synergistic effects on efficiency and selectivity.

Selective Electroreduction of 5-Hydroxymethylfurfural to Dimethylfuran in Neutral Electrolytes via Hydrogen Spillover and Adsorption Configuration Adjustment.

5-Hydroxymethylfurfural (HMF), one of the essential C6 biomass derivatives, has been deeply investigated in electrocatalytic reduction upgrading. Nevertheless, the high product selectivity and rational design strategy of electrocatalysts for electrocatalytic HMF reduction is still a challenge. Here, a high selective electro-reduction of HMF to dimethylfuran (DMF) on palladium (Pd) single atom loaded on titanium dioxide (Pd SA/TiO2 ) via hydrogen spillover and adsorption configuration adjustment in neutral electrolytes is achieved. Combining density functional theory calculations and in situ characterization, it is revealed that Pd single atom could weaken the interaction between Pd atoms and adsorbed hydrogen (*H) to promote the *H spillover for increasing *H coverage on the surface and maintain the tilted adsorption configuration to activate C═O bond; thus the selectivity of DMF on Pd SA/TiO2 increases to 90.33%. Besides, it is elaborated that low *H coverage on TiO2 favors the formation of bis(hydroxymethyl)hydro-furoin (BHH), and the flat adsorption configuration of HMF on Pd nanoparticles benefits to form 2,5-dihydroxymethylfuran (DHMF). This work provides a promising approach for modifying electrocatalysts to realize the selective electroreduction of HMF to value-added products.

Ligand engineering towards electrocatalytic urea synthesis on a molecular catalyst.

Electrocatalytic C-N coupling from carbon dioxide and nitrate provides a sustainable alternative to the conventional energy-intensive urea synthetic protocol, enabling wastes upgrading and value-added products synthesis. The design of efficient and stable electrocatalysts is vital to promote the development of electrocatalytic urea synthesis. In this work, copper phthalocyanine (CuPc) is adopted as a modeling catalyst toward urea synthesis owing to its accurate and adjustable active configurations. Combining experimental and theoretical studies, it can be observed that the intramolecular Cu-N coordination can be strengthened with optimization in electronic structure by amino substitution (CuPc-Amino) and the electrochemically induced demetallation is efficiently suppressed, serving as the origination of its excellent activity and stability. Compared to that of CuPc (the maximum urea yield rate of 39.9 ± 1.9 mmol h-1 g-1 with 67.4% of decay in 10 test cycles), a high rate of 103.1 ± 5.3 mmol h-1 g-1 and remarkable catalytic durability have been achieved on CuPc-Amino. Isotope-labelling operando electrochemical spectroscopy measurements are performed to disclose reaction mechanisms and validate the C-N coupling processes. This work proposes a unique scheme for the rational design of molecular electrocatalysts for urea synthesis.

Correlating the Valence State with the Adsorption Behavior of a Cu-Based Electrocatalyst for Furfural Oxidation with Anodic Hydrogen Production Reaction.

The low-potential furfural oxidation reaction (FFOR) on a Cu-based electrocatalyst can produce H2 at the anode, thereby providing a bipolar H2 production system with an ultralow cell voltage. However, the intrinsic activity and stability of the Cu-based electrocatalyst for the FFOR remain unsatisfactory for practical applications. This study investigates the correlation between the valence state and the adsorption behavior of the Cu-based electrocatalyst in furfural oxidation. Cu0 is the adsorption site with low intrinsic activity. Cu+ , which exists in the form of Cu(OH)ads in alkaline electrolytes, has no adsorption ability but can improve the performance of Cu0 by promoting the adsorption of FF. Moreover, a mixed-valence Cu-based electrocatalyst (MV Cu) with high intrinsic activity and stability is prepared electrochemically. With the MV Cu catalyst, the assembled dual-side H2 production electrolyzer has a low electricity requirement of only 0.24 kWh mH2 -3 at an ultralow cell voltage of 0.3 V, and it exhibits sufficient stability. This study not only correlates the valence state with the adsorption behavior of the Cu-based electrocatalyst for the low-potential FFOR with anodic H2 production but also reveals the mechanism of deactivation to provide design principles for Cu-based electrocatalysts with satisfactory stability.

Unraveling the electrophilic oxygen-mediated mechanism for alcohol electrooxidation on NiO.

Aqueous organic electrosynthesis such as nucleophile oxidation reaction (NOR) is an economical and green approach. However, its development has been hindered by the inadequate understanding of the synergy between the electrochemical and non-electrochemical steps. In this study, we unravel the NOR mechanism for the primary alcohol/vicinal diol electrooxidation on NiO. Thereinto, the electrochemical step is the generation of Ni3+-(OH)ads, and the spontaneous reaction between Ni3+-(OH)ads and nucleophiles is an electrocatalyst-induced non-electrochemical step. We identify that two electrophilic oxygen-mediated mechanisms (EOMs), EOM involving hydrogen atom transfer (HAT) and EOM involving C-C bond cleavage, play pivotal roles in the electrooxidation of primary alcohol to carboxylic acid and the electrooxidation of vicinal diol to carboxylic acid and formic acid, respectively. Based on these findings, we establish a unified NOR mechanism for alcohol electrooxidation and deepen the understanding of the synergy between the electrochemical and non-electrochemical steps during NOR, which can guide the sustainable electrochemical synthesis of organic chemicals.

Unveiling the Adsorption Behavior and Redox Properties of PtNi Nanowire for Biomass-Derived Molecules Electrooxidation.

Ni-based materials are auspicious electrocatalysts for 5-hydroxymethylfurfural oxidation reaction (HMFOR), including the adsorption and conversion of HMF and OHad on the electrocatalyst surface. However, the intrinsic HMFOR activity of Ni-based catalysts is far from satisfactory due to the weak adsorption of HMF and OHad species. Herein, a set of PtxNi100-x bundle nanowires (NWs) were prepared for HMFOR, which enables a low onset-potential and large current density. Operando methods reveal that Pt modulates the redox property of Ni in PtNi NWs and accelerates the oxidation of Ni2+-OH to Ni3+-O species during HMFOR. Moreover, the adsorption studies demonstrate the synergetic roles of Pt and Ni in enhancing the HMFOR activity by forming Pt-O-Ni bonds. In detail, Ni atoms modulate the d band of Pt to alter the adsorption behavior of HMF. Pt atoms promote the adsorption of OHad on Ni sites. This work provides design principles for HMFOR electrocatalysts by modulating the adsorption behaviors of organic molecules and OHad.

Activated Ni-OH Bonds in a Catalyst Facilitates the Nucleophile Oxidation Reaction.

The nucleophile oxidation reaction (NOR) is of enormous significance for organic electrosynthesis and coupling for hydrogen generation. However, the nonuniform NOR mechanism limits its development. For the NOR, involving electrocatalysis and organic chemistry, both the electrochemical step and non-electrochemical process should be taken into account. The NOR of nickel-based hydroxides includes the electrogenerated dehydrogenation of the Ni2+ -OH bond and a spontaneous non-electrochemical process; the former determines the electrochemical activity, and the nucleophile oxidation pathway depends on the latter. Herein, the space-confinement-induced synthesis of Ni3 Fe layered double hydroxide intercalated with single-atom-layer Pt nanosheets (Ni3 Fe LDH-Pt NS) is reported. The synergy of interlayer Pt nanosheets and multiple defects activates Ni-OH bonds, thus exhibiting an excellent NOR performance. The spontaneous non-electrochemical steps of the NOR are revealed, such as proton-coupled electron transfer (PCET; Ni3+ -O + X-H = Ni2+ -OH + X• ), hydration, and rearrangement. Hence, the reaction pathway of the NOR is deciphered, which not only helps to perfect the NOR mechanism, but also provides inspiration for organic electrosynthesis.

[Analysis on the literature concerning Angiostrongylus cantonensis and Angiostrongyliasis cantonensis].

OBJECTIVE: To explore the development of the study on Angiostrongylus cantonensis. METHODS: A total of 930 papers were searched from the PubMed and Chinese Bio-medical Disc(CBM) database under the search terms of Angiostrongylus cantonensis and analyzed through publication time, journal and contents. RESULTS: The number of papers published was found to increase annually, and two peaks of publication in national magazines occurred since 1996. Most papers were published in tropical medicine or professional journal of parasitology. The reports mostly documented cases and epidemiological investigations, and only a few investigated pathogenic mechanisms, drug treatment and other basic theory. CONCLUSION: It is in the initial stage of the study on Angiostrongylus cantonensis and Angiostrongyliasis, and there are a vast space in diagnosis, pathogenic mechanism, therapy and prevalence of Angiostrongyliasis cantonensis.