Electrocatalytic Oxidation Of Alcohols Research Articles

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 100mA/cm2 with a low energy input (∼1.63V). 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.

Regulation of Catalyst Immediate Environment Enables Acidic Electrochemical Benzyl Alcohol Oxidation to Benzaldehyde.

Electrocatalytic alcohol oxidation in acid offers a promising alternative to the kinetically sluggish water oxidation reaction toward low-energy H2 generation. However, electrocatalysts driving active and selective acidic alcohol electrochemical transformation are still scarce. In this work, we demonstrate efficient alcohol-to-aldehyde conversion achieved by reticular chemistry-based modification of the catalyst's immediate environment. Specifically, coating a Bi-based electrocatalyst with a thin layer of metal-organic framework (MOF) substantially improves its performance toward benzyl alcohol electro-oxidation to benzaldehyde in a 0.1 M H2SO4 electrolyte. Detailed analysis reveals that the MOF adlayer influences catalysis by increasing the reactivity of surface hydroxides as well as weakening the catalyst-benzaldehyde binding strength. In turn, low-potential (0.65 V) cathodic H2 evolution was obtained through coupling it with anodic benzyl alcohol electro-oxidation. Consequently, the presented approach could be implemented in a wide range of electrocatalytic oxidation reactions for energy-conversion application.

Electrochemical alcohol oxidation reaction on Precious‐Metal‐Free catalysts: Mechanism, activity, and selectivity

AbstractThe electrochemical alcohol oxidation reaction (AOR) is pivotal for the development of sustainable energy. The complete oxidation of alcohols has attracted extensive attention as a vital process in fuel cells. Moreover, as an alternative reaction to the oxygen evolution reaction, the selective oxidation of alcohols emerges as an effective means to lower the energy expenditure associated with electrolytic hydrogen production while yielding high‐value products. Nonprecious metal materials have been widely applied in the selective oxidation catalysis of alcohols due to their cost‐effectiveness and excellent durability. In recent years, leveraging the advantages of nonprecious metal materials in electrocatalytic AOR, researchers have delved into catalytic mechanisms and various efficient catalysts have been fabricated and evaluated. This review provides an overview of the current advancements in the electrocatalytic selective oxidation of diverse alcohols and the catalytic systems centered around nonprecious metal materials. It systematically summarizes the shared traits and distinctions in catalytic reaction characteristics across various systems, thereby laying the theoretical foundation for developing novel catalyst systems that are efficient, stable, and highly selective. This review will facilitate the utilization of nonprecious metal catalysts further toward the electrocatalytic oxidation of alcohols.

Electrochemical alcohol oxidation using a TEMPO nitroxide polymer as a homogeneous and surface‐confined catalyst

AbstractPolymers containing TEMPO moieties are effective catalysts for the electrochemical oxidation of alcohols. Such polymers, almost exclusively, are non‐commercial and are prepared using multi‐step synthetic procedures. Here we show that a commercially available TEMPO bearing polymer, Polyamine Immobilised Piperidinyl Oxyl (PIPO), is an effective homogeneous and surface‐confined polymeric catalyst for electrochemical alcohol oxidation at carbonaceous electrodes. We probe electrolytic conditions for effective and stable electrocatalytic alcohol oxidation showing that dichloromethane (DCM), containing tetrabutylammonium perchlorate (TBAP) and N‐methyl imidazole (NMI), is a suitable medium for homogeneous catalysis whilst carbonate buffer (pH 9.5) is better suited when PIPO is adsorbed at the electrode surface. These findings demonstrate the viability of PIPO as an effective and accessible catalyst for electrochemical alcohol oxidations.

Facile Synthesis of High-Entropy Alloy Nanowires for Electrocatalytic Alcohol Oxidation.

Considering the structural and compositional advantages of high-entropy alloy (HEA) as high-efficient electrocatalysts, we here present a facile method to prepare high-entropy alloy nanowires with seven elements in an aqueous solution. The as-synthesized PdPtCuAgAuPbCo nanowires possess dispersed one-dimensional morphology and exhibit enhanced electrocatalytic performance with the mass activity of 9.9 A mgPd+Pt -1 toward ethanol electrooxidation. The HEA nanowires also perform superior stability, resistance to CO poisoning, and good electrocatalytic activities toward other alcohols (e. g., ethylene glycol and methanol) oxidation. The synthesis strategy is easy to operate with low cost and has wide application prospects for preparing desired electrocatalysts for fuel cells.

Molybdenum–Based Electrocatalysts for Direct Alcohol Fuel Cells: A Critical Review

<p>Direct alcohol fuel cells (DAFCs) have gained much attention as promising energy conversion devices due to their ability to utilize alcohol as a fuel source. In this regard, Molybdenum-based electrocatalysts (Mo-ECs) have emerged as a substitution for expensive Pt and Ru–based co-catalyst electrode materials in DAFCs, owing to their unique electrochemical properties useful for alcohol oxidation. The catalytic activity of Mo-ECs displays an increase in alcohol oxidation current density by several folds to 1000–2000 mA mg<sub>Pt</sub><sup>−1</sup>, compared to commercial Pt and PtRu catalysts of 10–100 mA mg<sub>Pt</sub><sup>−1</sup>. In addition, the methanol oxidation peak and onset potential have been significantly reduced by 100–200 mV and 0.5–0.6 V, respectively. The performance of Mo-ECs in both acidic and alkaline media has shown the potential to significantly reduce the Pt loading. This review aims to provide a comprehensive overview of the bifunctional mechanism involved in the oxidation of alcohols and factors affecting the electrocatalytic oxidation of alcohol, such as synthesis method, structural properties, and catalytic support materials. Furthermore, the challenges and prospects of Mo-ECs for DAFCs anode materials are discussed. This in-depth review serves as valuable insight toward enhancing the performance and efficiency of DAFC by employing Mo-ECs.</p>

Investigation on the electrocatalytic oxidation of alcohol using zinc oxide thin films deposited by pulsed electrodeposition on an indium tin oxide surface

To perform electro-catalytic oxidation of alcohols in an alkaline media, zinc oxide (ZnO) thin films were effectively deposited on indium tin oxide (ITO) substrates using the pulsed electrodeposition (PE) method in a zinc nitrate aqueous solution. Analyses of microstructural, photoelectrochemical, and optical characteristics of ZnO thin films were performed as a function of pulsed electrodeposition parameters. XRD analysis was applied to determine structural properties, and SEM and AFM analysis were used to investigate morphological characteristics. X-ray diffraction analyses revealed that the produced films were polycrystalline and had a (002) preferentially oriented, hexagonal wurtzite structure. The morphology of ZnO has improved in the direction of nanorod films, as evidenced by scanning electron microscopy (SEM) and atomic force microscopy (AFM) images. UV transmittance data was used using Tauc's relationship to determine the film's bandgap to be 3.26 eV. The photocurrent response shows that ZnO films have high values, at 305.17 A/cm2, and good optical characteristics. The electrocatalytic oxidation of methanol was finally evaluated on the films. After being optimized in the pulsed electrodeposition mode, ZnO thin film characteristics and methanol electrocatalytic oxidation both saw substantial improvements.

Microwave-assisted synthesis of ZIF-9@xGO composites as cooperative electrocatalysts for electro-oxidation of benzyl alcohols coupled with H2 production

We report microwave assisted rapid synthesis of ZIF-9 nanocrystals. ZIF-9@xGO composites displayed selective electrocatalytic oxidation of benzyl alcohols (benzoic acid yield 84%, faradaic efficiency 88%) together with high H2 production (273 mmol g−1 h−1).

Catalytic Activity of Au-Cu Alloy on TiO2 Nanotubes for Alcohol Oxidation

First fuel cell was discovered 180 years ago and still the ideal, namely cheap and effective catalytic materials are highly required. Such device allows to convert chemical energy into electrical one without pollutant gasses emission. In the case of alcohol fuel cells, methanol, ethanol, ethylene glycol and glycerine are considered as a power source. Platinum is commonly used for alcohol electrocatalyst, because of its high activity and stability. However, due to the high cost and limited supply platinum should be replaced by material that small amount is enough to reach satisfactory catalytic effect. In our work, we present the activity of gold-copper modified titania nanotubes toward electrocatalytic alcohol oxidation [1].The material is fabricated using three steps such as: 1) anodization of Ti plate, 2) thin 10 nm AuCu alloy layer magnetron sputtering, and 3) rapid thermal annealing in an argon atmosphere [2]. Scanning electron microscopy confirmed the presence of well-ordered TiO2 nanotubes (TiNT) with diameter of 101 ± 13 nm and length of 709± 53 nm. After AuCu alloy magnetron sputtering and thermal treatment spherical nanoparticles were formed on NT surface. Based on top view SEM images the diameter of gold copper nanoparticles is equal to 38 ± 5 nm. However, the TEM images showed that diameter of nanoparticles changes from 5 nm to 60 nm (Figure 1a-d) where the bigger particles are on the top of the nanotubes. Applied fabrication procedure allowed us to obtain electrode material that can be used in methanol, ethylene glycol or glycerine oxidation. The highest catalytic activity of AuCu alloy was obtained for glycerine oxidation. Prepared material exhibited 90 times higher current density after glycerine addition to the alkaline solution than pure TiNT (Figure 1e). Furthermore, higher current density towards alcohol oxidation was registered for thermally annealed sample (an-AuCu/TiNT) than for non-annealed one (n-AuCu/TiNT).Cyclic voltammetry measurements for the an-AuCu/TiNT in glycerine solution at different scan rates confirmed diffusion controlled process. The oxidation peak current density located at +0.3 V and +1 V grows up to 120 mV/s with slope of 51 and 81 µA/cm2 respectively, which confirmed more privilege process at +1 V vs. Ag/AgCl/0.1M KCl. We believe that the information reported in our work provide wider knowledge about new and more efficient electrodes for alcohol oxidation.Research is financed by National Science Centre (Poland): Grant No. 2019/35/N/ST5/02604[1] W. Lipińska et al. Journal of Materials Science, 57 (2022) 13345, DOI:10.1007/s10853-022-07471-7[2] W. Lipińska et al. ACS Applied Materials & Interfaces, 13 (2021) 52967, DOI:10.1021/acsami.1c16271 Figure 1

Anode Catalysts for Electrocatalytic Alcohol Oxidation Coupled to CO2 Reduction in Continuous-Flow Electrolyzers

Thanks to the intense scientific interest, the field of CO2 electrolysis witnessed remarkable progress (industrially relevant partial current densities, selective electrocatalysts towards small molecule products, multi-cell stacks, etc.) in the past decade. However, despite all these efforts, the energy efficiency of CO2 electrolyzers is still relatively low, which is rooted in the large cell voltages. A reason behind this is that the kinetically sluggish water oxidation (OER) is performed at the anode in parallel with CO2 reduction (CO2RR) at the cathode. This issue can be circumvented by coupling CO2RR with alternative anode processes, resulting in smaller cell voltage (better energy efficiency) along with the possible generation of products at the anode with high market value. Thus, maximizing the potential of utilizing waste carbon sources to generate value-added products. Such alternative reactions include, for example, the electrocatalytic oxidation of chloride ions, aliphatic and aromatic alcohols, amines, urea, hydrazine, and numerous biomass-derived substances such as 5-(hydroxymethyl)furfural, sorbitol, etc.In this study, CO2RR to CO was driven at the cathode, and the electrocatalytic oxidation of glycerol (GOR) was performed at the anode of a small (1 cm2 active surface area) microfluidic electrolyzer cell. Ir black was replaced by carbon-supported Pt nanoparticles, while Ag nanoparticles were used as the cathode catalyst. During our experiments, we identified four main factors influencing the GOR activity and selectivity: i) the quality and quantity of the used ionomer, ii) the electrolyte flow rate, iii) glycerol concentration, and iv) the applied anode potential. The latter was particularly important since Pt showed the highest activity toward GOR in a potential window where its surface starts to oxidize. The formation of a continuous oxide layer has to be avoided since it inhibits the alcohol oxidation reaction. By setting optimal conditions, a close to 100% Faradic efficiency (FE) toward CO formation on the cathode and between 70-80% FE toward GOR was achieved above 200 mA cm-2 total current density. The amount of the formed products were tracked by mass spectrometry, gas-, and high-performance liquid chromatography, and nuclear magnetic resonance spectroscopy. Dihydroxyacetone, glycerate, glycolate, oxalate, tartronate, formate, and lactate were identified as GOR products. The missing charge was attributed to the formation and a small amount of CO2. To improve the stability and selectivity of Pt in GOR, semipermeable metal oxide layers were introduced to the top of the catalyst layer. The thin films were synthesized by electrodeposition in different thicknesses. Based on our measurements, a set of criteria were defined regarding the composition of the anode catalyst layer (ionomer, co-catalyst overlayer, etc.), the composition of the electrolyte solution, and the applied electrochemical protocol to allow stable and selective GOR at high achievable current densities.

Graphene as a Platform in Surface-Enhanced Infrared Absorption Spectroscopy (SEIRAS) for Amino-TEMPO Electro-Grafting

2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) has emerged as an environmentally benign catalyst for the electrochemical oxidation of primary and secondary alcohols to aldehydes and ketones (1). This simple organic free radical reagent possesses high activity, and versatility, and is one of the most promising alternatives to noble metal catalysts that were previously studied. The catalytic activity and reactivity of TEMPO is mostly studied in bulk solutions, for fuel cells, aqueous redox flow batteries and sensors (2, 3). For more practicality, various approaches were developed to immobilize TEMPO on active supports, such as anionic polyelectrolytes, and the electropolymerization of TEMPO-substituted pyrrole or thiophene (4, 5). However, these substrates suffer from instability, loss of catalytic activity, degradation of the polymer film in alkaline environment mostly used for TEMPO regeneration. One other way, is to use carbon-based substrates that are stable in aqueous acid and base environment, as well as non-aqueous solutions and have shown enhanced electrocatalytic behavior (6, 7).In this work, we studied the electro-grafting of amino-TEMPO on graphene using in-situ attenuated total reflection infrared absorption spectroscopy (ATR-IRAS). We observed that TEMPO is attached on the surface through covalent bonding between the amine and the graphene lattice, as previously reported (6, 7). While grafting was successfully demonstrated via the oxidation of the primary amine to a radical cation which reacted with the graphene surface, ATR-surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) provided additional spectral feature confirming TEMPO grafting through plasmon induced signal enhancement. Hickey, D. P.; Milton, R. D.; Chen, D.; Sigman, M. S.; Minteer, S. D., TEMPO-Modified Linear Poly(ethylenimine) for Immobilization-Enhanced Electrocatalytic Oxidation of Alcohols. ACS Catalysis 2015, 5 (9), 5519-5524. Mishra, A.; Kim, J.; Zorigt, M.; Romo, A. I. B.; Gaddam, R.; Braun, J. E.; Ziviani, D.; Rodríguez-López, J., Highly Selective TEMPO Catalyzed Bulk Electrooxidation of Isopropanol to Acetone for Application in Electrochemical Heat Pumping. ACS Sustainable Chemistry & Engineering 2023, 11 (16), 6241-6249. Elouarzaki, K.; Mandoc, L.-R. P.; Gorgy, K.; Holzinger, M.; Amarandei, C.-A.; Ungureanu, E.-M.; Cosnier, S., Synthesis and electrochemical characterization of original “TEMPO” functionalized multiwall carbon nanotube materials: Application to iron (II) detection. Electrochemistry Communications 2015, 60, 131-134. Belgsir, E. M.; Schäfer, H. J., Selective oxidation of carbohydrates on Nafion®–TEMPO-modified graphite felt electrodes. Electrochemistry Communications 2001, 3 (1), 32-35. Grimshaw, J.; Perera, S. D., Poly(pyrrole-pyromellitimide) modified electrodes. Journal of Electroanalytical Chemistry and Interfacial Electrochemistry 1990, 278 (1), 279-286. Barman, K.; Askarova, G.; Jia, R.; Hu, G.; Mirkin, M. V., Efficient Voltage-Driven Oxidation of Water and Alcohols by an Organic Molecular Catalyst Directly Attached to a Carbon Electrode. Journal of the American Chemical Society 2023, 145 (10), 5786-5794. Yuan, B.; Xu, C.; Zhang, D.; Zhang, R.; Su, H.; Guan, P.; Nie, J.; Fernandez, C., Electrografting of amino-TEMPO on graphene oxide and electrochemically reduced graphene oxide for electrocatalytic applications. Electrochemistry Communications 2017, 81, 18-23.

Enhanced electrocatalytic alcohol oxidation mediated with ultra-low concentration of aminoxyl radicals via an Intermediate-Rich local microenvironment

Indirect electrocatalytic alcohol oxidation mediated by aminoxyl radicals generally requires large amounts of aminoxyl radicals to activate the oxidation of alcohols, which limits its potential for industrial utilization. In this study, the cavity structure of carbonaceous nano-volcanoes (CNV) grown on 3D graphite felt as nanoreactors advantageously provides a microenvironment with high compartmentalised reactant concentrations for efficient electrocatalytic alcohol oxidation. By extending the retention time of reactant molecules in the CNV through cavity enrichment, their interaction probability with the electrodes was maximized, resulting in the intensification of mass transport and kinetically favorable settings. Meanwhile, abundant oxygen-containing functional groups on the surface constructed by the CNV provided hydrogen bonding forces to anchor the reactive aminoxyl radicals (4-acetamido-2,2,6,6-tetrame-thylpi-peridin-1-oxyl, ACT) during the reaction. Based on the intermediate-rich local microenvironment, a high turnover frequency of up to 31818 h−1 can be achieved even with only 0.5 mol% ACT-mediated. The electrocatalytic oxidation of benzyl and heterocyclic substrates can be achieved by this method under mild conditions. To showcase the synthetic efficacy and practical applicability of this approach, the successful oxidation of a chiral primary alcohol precursor to the generic drug levetiracetam was demonstrated on a larger scale, presenting further evidence of its practicality and usefulness in chemical synthesis.

Process intensification enhanced continuous flow for the effective coupling of sterol electrooxidation with H2 evolution using NiMo-based electrocatalysts

The electrocatalytic oxidation (ECO) of steroid alcohols at the anode is sustainable approach to synthesize valuable steroid carbonyls. This process is coupled with the hydrogen evolution reaction (HER) occurring at the cathode, further enhancing its environmental benefits. However, determining compatible electrocatalysts facilitating production of steroid carbonyls and hydrogen poses challenge. Hence, synergistically enhanced electrocatalytic approach was proposed, whereby NiMoO4 and the aminoxyl radical mediator 4-acetamido-TEMPO (ACT) were used together at the anode, in combination with Ni0.2Mo0.8N at the cathode. In situ experiments and theoretical calculations revealed that the introduction of Mo facilitates the formation of NiOOH and provides stabilization of ACTH (the reduced form of ACT) on the NiMoO4 surface. The effect of Mo also contributed to avoid the H* over-binding to decrease the HER energy barrier. This study aims to establish systematic approach towards the rational design of electrocatalysts that can be used to produce value-added steroid carbonyls and H2.

Modification Strategies for Development of 2D Material-Based Electrocatalysts for Alcohol Oxidation Reaction.

2D materials, such as graphene, MXenes (metal carbides and nitrides), graphdiyne (GDY), layered double hydroxides, and black phosphorus, are widely used as electrocatalyst supports for alcohol oxidation reactions (AORs) owing to their large surface area and unique 2D charge transport channels. Furthermore, the development of highly efficient electrocatalysts for AORs via tuning the structure of 2D support materials has recently become a hot area. This article provides a critical review on modification strategies to develop 2D material-based electrocatalysts for AOR. First, the principles and influencing factors of electrocatalytic oxidation of alcohols (such as methanol and ethanol) are introduced. Second, surface molecular functionalization, heteroatom doping, and composite hybridization are deeply discussed as the modification strategies to improve 2D material catalyst supports for AORs. Finally, the challenges and perspectives of 2D material-based electrocatalysts for AORs are outlined. This review will promote further efforts in the development of electrocatalysts for AORs.

Selective electrocatalytic conversion of primary alcohols to nitriles on nickel-cobalt nitride/oxide tandem electrocatalyst

Nitriles are vital precursors in the production of pharmaceuticals, advanced materials and many other commercial chemicals. Conventional approaches for nitrile synthesis are limited by the utilization of highly toxic cyanide ion and harsh conditions. The electrochemical conversion of primary alcohols and ammonia to nitriles offers a cost-effective and green approach to prepare nitriles, which requires highly efficient and selective catalysts to drive the cascade reaction and minimize side reactions. Here, we demonstrate how nitriles can be selectively synthesized by electrocatalytic oxidation of benzyl alcohol and ammonia on NiCo nitride and oxide that are co-localized on carbon cloth (NiCo-N,O/CC) electrode. In this electrocatalyst, the oxidation from alcohols to aldehydes is mainly catalyzed by NiCo oxide, while the oxidation from imine to nitrile is mainly catalyzed by NiCo nitride, endorsing preferential oxidation and cascade reactions on these catalytic interfaces. A total faradaic efficiency of 52%, productivity rate of 35 μmol cm-2h−1 and 70.1% selectivity of nitriles was achieved at 1.53 V vs RHE. The two interface NiCo-N,O/CC tandem electrocatalyst revealed synergistic activity and selectivity superior to NiCo-O/CC with single interface. Our results demonstrate that the utilization of tandem catalytic mechanisms could create new prospects in designing electrocatalysts for cascade reactions.

Fe Electron Center Local Regulation of CoFe‐Layered Double Hydroxides Nanosheets for Enhancing the Electrocatalytic Oxidation of Benzyl Alcohol

AbstractReplacing sluggish oxygen evolution reaction (OER) with electrocatalytic oxidation (ECO) of alcohols was a promising hotspot due to its advantages of requiring low potential, inhibiting mixing of gases, and forming value‐added products. In the ECO of alcohols process, Fe electron centers of Fe‐based layered double hydroxides (LDHs) can regulate the d band of LDHs overlap, optimize the active local structure of LDHs, and then enhance the electrocatalytic oxidation performance. In this work, CoxFey‐LDHs nanosheets with different ratios of Co/Fe were prepared for selective ECO of benzyl alcohol (BA) to benzoic acid (BAC). Comprehensive characterizations revealed that the adjustment of bandgap and OH species adsorption of CoxFey‐LDHs resulted in the appropriate thermodynamic driving force, which improved the electrical conductivity of CoxFey‐LDHs and enhanced their ECO of BA. Especially, the as‐prepared Co3Fe1‐LDH showed intriguing electrocatalytic activity and only required a potential of 1.51 V (vs. RHE) to achieve a total current density of 50 mA cm−2 in alkaline solution containing 10 mM BA with a conversion (96.79 %) of BA and selectivity (94.93 %) of BAC, which was 60 mV lower than that of OER. After six cycles, Co3Fe1‐LDH still achieved 94.74 % conversion of BA and 92.10 % selectivity of BAC without significant degradation.

Enhanced electrocatalytic glycerol oxidation on CuCoN0.6/CP at significantly reduced potentials

Electrocatalytic alcohol oxidation coupled with the hydrogen evolution reaction, wherein a thermodynamically favorable oxidation reaction replaces the sluggish kinetics of the oxygen evolution reaction, has recently attracted considerable attention. However, the development of nonprecious-metal electrocatalysts capable of delivering much lower oxidation potentials holds great significance. In this study, we proposed and developed CuCoN0.6 nanowires loaded on conductive carbon paper (denoted as CuCoN0.6/CP) as an efficient catalyst for selective glycerol oxidation to formate. Our catalyst achieved a remarkably high faradic efficiency of 90.0% towards formate production. More notably, it required an anode potential as low as 1.07 V to achieve a current density of 10 mA cm−2, a significantly lower potential than that reported in the literature. Experimental characterizations reveal that the oxidations of Cu+ and Co2+ ions promoted the formation of reactive hydroxyl species, which are responsible for the substantially reduced oxidation potential and enhanced glycerol oxidation performance. Furthermore, we investigated the reaction pathway of glycerol oxidation and structural changes in the catalysts. The catalyst reconstruction led to the formation of CoOOH, which is considered as the active site for glycerol oxidation. Finally, we successfully separated high-purity and value-added potassium diformate product. This work not only advances the electrocatalytic conversion of biomass-derived alcohols but also provides insights into the design of electrocatalysts with broad applications.

Selective electrooxidation of 2-hydroxybenzyl alcohol coupled with H2 production promoted by surface reconstruction of β-Ni(OH)2 nanosheets

2-Hydroxybenzaldehyde (SALD) exhibits special reactivity in various chemical reactions due to the existence of aldehyde and hydroxyl groups, which also make it a challenge to achieve high conversion and selectivity for SALD production. Herein, β-Ni(OH)2 nanosheets over nickel foam (NF) at different hydrothermal temperatures were synthesized for electrocatalytic oxidation (ECO) of 2-hydroxybenzyl alcohol (SAL) into SALD. The β-Ni(OH)2 electrode obtained at 160 °C achieves the best ECO performance in 2.5 M KOH at the applied potential of 1.45 V (RHE), showing the SALD selectivity of 78.90% and the Faradaic efficiency of 87.94% at the SAL conversion of 69.76%. ECO of SAL reduces the cell voltage and boosts the hydrogen productivity by 2.74 times. It is of great importance to find that potential-driven surface reconstruction of β-Ni(OH)2 enables selective conversion of SAL into SALD. Side reactions including OER as well as oxidation of phenolic group can be effectively controlled via regulating applied potentials on β-Ni(OH)2. This work is the first report on direct electrochemical oxidation of SAL with high SALD selectivity, and offers a green and clean strategy for highly selective production of SALD under mild conditions.

Oxidant-Free Electrochemical Direct Oxidative Benzyl Alcohols to Benzyl Aldehydes Using Three-Dimensional Printing PPAR Polyoxometalate.

The oxidation of benzyl alcohols is an important reaction in organic synthesis. Traditional methods for benzyl alcohol oxidation have not been widely utilized due to the use of significant amounts of precious metals and environmentally unfriendly reagents. In recent years, electrocatalytic oxidation has gained significant attention, particularly electrochemical anodic oxidation, which offers a sustainable alternative for oxidation without the need for external oxidants or reducing agents. Here, a copper monosubstituted phosphotungstate-based polyacrylate resins (Cu-LPOMs@PPAR) catalyst has been fabricated with immobilization and recyclability using 3D printing technology that can be successfully applied in the electrocatalytic oxidation of benzyl alcohol to benzaldehyde, achieving atom economy and reducing pollution. In this protocol, we obtain benzaldehyde in good yields with excellent functional group toleration under metal-free and oxidant-free conditions. This strategy could provide a new avenue for heterogeneous catalysts in application for enhancing the efficiency and selectivity of electrocatalytic oxidation processes.

Pyrolysis of ZIF-8 to PdZn alloy nanoparticles on carbon doping with nitrogen for highly efficient electrocatalytic alcohol oxidation

MOFs (metal-organic frameworks) materials have been widely applied in sensing and catalysis, with the advantages of large surface area, numerous active sites, controllable size and morphology. Herein, we report the preparation of the caged PdZn/NC catalysts with the PdZn alloy nanoparticles on carbon doping with nitrogen owing high electrocatalytic performance by using a hydrothermal synthesis and pyrolysis strategy. The caged structure and PdZn alloy are demonstrated by a series of advanced characterization techniques. The material combines the advantages of bimetallic alloy and MOFs cage structure to realize highly efficient electrocatalytic oxidation of ethanol oxidation reactions (EOR) and methanol oxidation reactions (MOR) simultaneously. Electrochemical test results show that PdZn/NC-2 has a mass activity of 2.41 A mg−1pd and 2.64 A mg−1pd for methanol and ethanol oxidation, respectively, which is 12.68 times (MOR) and 14.67 times (EOR) higher than that of commercial Pd/C. This is probably attributed to the cage-like structure of PdZn/NC separating the Pd nanoclusters, resulting in high Pd dispersion. Simultaneously, the electronic property of Pd is adjusted after the formation of the complete PdZn alloy, improving the desorption of the carbon-based intermediates from the Pd active sites. This increases the CO poisoning resistance, resulting in good alcohol electrocatalytic oxidation activity and stability.