Electrooxidation Of Alcohols Research Articles

Microscopic-Level Insights into P-O-Induced Strong Electronic Coupling Over Nickel Phosphide with Efficient Benzyl Alcohol Electrooxidation.

Electrooxidation of biomass into fine chemicals coupled with energy-saving hydrogen production for a zero-carbon economy holds great promise. Advanced anode catalysts determine the cell voltage and electrocatalytic efficiency greatly, further the rational design and optimization of their active site coordination remains a challenge. Herein, a phosphorus-oxygen terminals-rich species (Ni2P-O-300) via an anion-assisted pyrolysis strategy is reported to induce strong electronic coupling and high valence state of active nickel sites over nickel phosphide. This ultimately facilitates the rapid yet in-situ formation of high-valence nickel with a high reaction activity under electrochemical conditions, and exhibits a low potential of 1.33V vs. RHE at 10mAcm-2, exceeding most of reported transition metal-based catalysts. Advanced spectroscopy, theoretical calculations, and experiments reveal that the functional P-O species can induce the favorable local bonding configurations for electronic coupling, promoting the electron transfer from Ni to P and the adsorption of benzyl alcohol (BA). Finally, the hydrogen production efficiency and kinetic constant of BA electrooxidation by Ni2P-O-300 are increased by 9- and 2.8- fold compared with the phosphorus-oxygen terminals-deficient catalysts (Ni2P-O-500). This provides an anion-assisted pyrolysis strategy to modulate the electronic environment of the Ni site, enabling a guideline for Ni-based energy/catalysis systems.

Bimetallic NiWO4 as an Efficient Interface Modulator for Pd Towards Enhanced Alcohol Electro-oxidation

Bimetallic NiWO4 as an Efficient Interface Modulator for Pd Towards Enhanced Alcohol Electro-oxidation

Competition between the oxygen evolution reaction and the electrooxidation of alcohols on heteroatom-functionalized multi-walled carbon nanotubes-supported Ni oxide catalysts

Hybrid water electrolysis is a prominent route for hydrogen production that circumvents issues related to the oxygen evolution reaction (OER), the anode process in conventional water electrolysis, by integrating an alternative anode reaction. Herein, samples of nickel oxide nanoparticles supported on oxygen and nitrogen-functionalized multi-walled carbon nanotubes were evaluated as electrocatalysts for the OER and the electrooxidation of methanol (MOR), ethanol (EOR) and glycerol (GOR). The trend of overpotentials measured at a current of 0.1 mA was OER > MOR > EOR > GOR, with slightly lower overpotentials observed for the nitrogen-doped sample, which is attributed to differences in nanoparticle size and distribution, support defectiveness, and nitrogen-induced electronic effects. The production of oxygen was monitored by Differential Electrochemical Mass Spectrometry (DEMS), indicating that the competition between OER and alcohol electrooxidation can be modulated by the support properties as well as by the nature and concentration of the alcohol.

Electrocatalytic Oxidation of Methanol and Ethanol with 3d-Metal Based Anodic Electrocatalysts in Alkaline Media Using Carbon Based Electrode Assembly.

Homogeneous electrocatalytic systems based on readily available, earth-abundant, inexpensive base metals Ni, Co, and Cr have been formulated for the electro-oxidation of alcohols (methanol and ethanol) that constitute a key half-cell component of direct alcohol fuel cells (DAFCs). Notably, excellent results were obtained for both methanol as well as ethanol electro-oxidation while operating with a half-cell assembly based on all-non-noble working and counter electrode systems consisting of glassy carbon and graphite rod, respectively. Using NaOH as the supporting electrolyte, Ni/Co/Cr metal salts and their bis(iminopyridine) complexes have been used as anodic electrocatalysts for the alcohol half-cell reactions, and among them, catalytic systems based on Co outperformed the corresponding systems based on Ni and Cr. The system comprising CoCl2.·6H2O [10 mM] + NaOH [6 M] at room temperature emerged as the best electrocatalyst for both methanol [5 M] electro-oxidation (ca. 522.5 ± 13.5 mA cm-2 at 1.4 V) and ethanol [5 M] electro-oxidation (ca. 209 ± 25 mA cm-2 at 1.34 V). It was observed that regardless of the starting alcohol, the end product is carbon dioxide, all of which gets trapped as sodium carbonate (up to 97% yield), thereby mitigating any possible hazards of greenhouse gas emission. Inferences obtained from FETEM, FESEM, and EDS analysis of both the electrolyte solution and residues deposited on the electrode surface provide evidence for the mostly homogeneous nature of the reaction mixture with the molecular catalyst being the major contributor toward the electrocatalytic activity apart from the minor role played by trace heterogeneous particles. The current cell assembly operating with non-noble working and counter electrodes utilizing a catalytic system based on an earth-abundant, base metal salt/complex that not only results in good half-cell current densities for high-energy power-source DAFCs but also generates high-value sodium carbonate offers an exciting avenue.

Electro-oxidation of alcohols over electrochemically activated nickel alloys for energy-saving hydrogen production

High-valence metal species generated via in situ electrochemical activation effectively enhance the adsorption of small organic molecules on the alloy surface.

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).

Bifunctional PdMoPt trimetallene boosts alcohol-water electrolysis.

Substituting oxygen evolution with alcohol oxidation is crucial for enhancing the cathodic hydrogen evolution reaction (HER) at low voltages. However, the development of high-performance bifunctional catalysts remains a challenge. In this study, an ultrathin and porous PdMoPt trimetallene is developed using a wet-chemical strategy. The synergetic effect between alloying metals regulates the adsorption energy of reaction intermediates, resulting in exceptional activity and stability for the electrooxidation of various alcohols. Specifically, the mass activity of PdMoPt trimetallene toward the electrooxidation of methanol, ethylene glycol, and glycerol reaches 6.13, 5.5, and 4.37 A mgPd+Pt -1, respectively. Moreover, the catalyst demonstrates outstanding HER activity, requiring only a 39 mV overpotential to achieve 10 mA cm-2. By employing PdMoPt trimetallene as both the anode and cathode catalyst, we established an alcohol-water hybrid electrolysis system, significantly reducing the voltage requirements for hydrogen production. This work presents a promising avenue for the development of bifunctional catalysts for energy-efficient hydrogen production.

Recent progress in transition metal based catalysts and mechanism analysis for alcohol electrooxidation reactions

This article reviews recent advancements in AOR catalysts, emphasizing mechanistic studies through in situ characterization and DFT calculations to unravel the structure-performance correlation.

A universal synthesis strategy of Pd-based trimetallic nanowires for efficient alcohol electrooxidation.

Trimetallic nanowires (NWs) have drawn much attention in efficient alcohol oxidation reaction (AOR) due to their unique features, including high atomic utilization efficiency and fast electron transfer ability. However, a universal strategy to synthesize Pd-based trimetallic NWs with high catalytic performance is still lacking. Herein, we develop a universal method for facile synthesis of PdBiM (M = Pt, Ru, Ir, Co, Cu) NWs with excellent AOR activities. By taking PdBiPt NWs as an example, the formation mechanism was investigated, and it is found that introduction of bismuth (Bi) plays an important role in facilitating the formation of the NW structure. Moreover, the PdBiPt NWs deliver an outstanding performance toward both the ethanol oxidation reaction (EOR) and the methanol oxidation reaction (MOR). Density functional theory (DFT) calculations together with experimental results disclose that the moderate electronic structure of trimetallic PdBiPt NWs can optimize the adsorption of OHads and weaken the adsorption of COads, thereby leading to the substantially enhanced AOR performance. We believe that this work can inspire the design of multimetallic NWs as high-performance catalysts.

2D petal-like PdAg nanosheets promote efficient electrocatalytic oxidation of ethanol and methanol.

The development of efficient alcohol electrooxidation catalysts is of vital importance for the commercialization of direct liquid fuel cells. As emerging advanced catalysts, two-dimensional (2D) noble metal nanomaterials have attracted much research attention due to their intrinsic structural advantages. Herein, we report the synthesis of petal-like PdAg nanosheets (NSs) with an ultrathin 2D structure and jagged edges via a facile wet-chemical approach, combining doping engineering and morphology tuning. Notably, the highly active sites and Pd-Ag composition endowed PdAg NSs with improved toxicity tolerance and substantially improved the durability toward the ethanol/methanol oxidation reaction (EOR/MOR). Moreover, the electronic effect and synergistic effect significantly enhanced the EOR and MOR activities in comparison with Pd NSs and commercial Pd/C. This work provides efficient catalysts for fuel electrooxidations and deep insight into the rational design and fabrication of novel 2D nanoarchitecture.

Vacancy‐induced catalytic mechanism for alcohol electrooxidation on nickel‐based electrocatalyst

AbstractOwing to outstanding performances, nickel‐based electrocatalysts are commonly used in electrochemical alcohol oxidation reactions (AORs), and the active phase is usually vacancy‐rich nickel oxide/hydroxide (NiOxHy) species. However, researchers are not aware of the catalytic role of atom vacancy in AORs. Here, we study vacancy‐induced catalytic mechanisms for AORs on NiOxHy species. As to AORs on oxygen‐vacancy‐poor β‐Ni(OH)2, the only redox mediator is electrooxidation‐induced electrophilic lattice oxygen species, which can only catalyze the dehydrogenation process (e.g., the electrooxidation of primary alcohol to carboxylic acid) instead of the C−C bond cleavage. Hence, vicinal diol electrooxidation reaction involving the C−C bond cleavage is not feasible with oxygen‐vacancy‐poor β‐Ni(OH)2. Only through oxygen vacancy‐induced adsorbed oxygen‐mediated mechanism, can oxygen‐vacancy‐rich NiOxHy species catalyze the electrooxidation of vicinal diol to carboxylic acid and formic acid accompanied with the C−C bond cleavage. Crucially, we examine how vacancies and vacancy‐induced catalytic mechanisms work during AORs on NiOxHy species.

Vacancy-induced catalytic mechanism for alcohol electrooxidation on nickel-based electrocatalyst.

Owing to outstanding performances, nickel-based electrocatalysts are commonly used in electrochemical alcohol oxidation reactions (AORs), and the active phase is usually vacancy-rich nickel oxide/hydroxide (NiOx Hy ) species. However, researchers are not aware of the catalytic role of atom vacancy in AORs. Here, we study vacancy-induced catalytic mechanisms for AORs on NiOx Hy species. As to AORs on oxygen-vacancy-poor β-Ni(OH)2 , the only redox mediator is electrooxidation-induced electrophilic lattice oxygen species, which can only catalyze the dehydrogenation process (e.g., the electrooxidation of primary alcohol to carboxylic acid) instead of the C-C bond cleavage. Hence, vicinal diol electrooxidation reaction involving the C-C bond cleavage is not feasible with oxygen-vacancy-poor β-Ni(OH)2 . Only through oxygen vacancy-induced adsorbed oxygen-mediated mechanism, can oxygen-vacancy-rich NiOx Hy species catalyze the electrooxidation of vicinal diol to carboxylic acid and formic acid accompanied with the C-C bond cleavage. Crucially, we examine how vacancies and vacancy-induced catalytic mechanisms work during AORs on NiOx Hy species.

Supported High‐Entropy Alloys for Electrooxidation of Benzyl Alcohol Assisted Water Electrolysis

AbstractElectrocatalytic hydrogen production technology is essentially vital for future green and sustainable energy revolution while its large‐scale industrial application is still unsatisfactory due to the low efficiency of electrocatalysts and kinetically sluggish oxygen evolution reaction (OER). Developing novel electrocatalysts and coupling them with upgrading organic molecules are considered effective solutions. Herein, it reports a high‐entropy composite electrocatalyst consisting of FeCoNiAlMo alloy and carbon nanotube (CNT) for anodic benzyl alcohol (BA) electrooxidation coupled with cathodic hydrogen production. Because of the lower charge transfer resistance and faster reaction kinetics, the quinary FeCoNiAlMo/CNT is highly active to OER, remarkably outperforming the ternary FeCoNi/CNT counterpart. Then, the FeCoNiAlMo/CNT composite electrocatalyst is further utilized for BA oxidation reaction‐assisted hydrogen evolution. Combining the experimental and calculation results, the different activities when tested in BA‐containing or BA‐free electrolytes can be attributed to the different metal active sites with specific surface adsorption effects to water and BA molecules, respectively. This work develops a novel electrocatalyst for high‐efficient alcohol oxidation‐assisted electrolysis.

Palladium chalcogenide nanosheets with p-d orbital hybridization for enhanced alcohol electro-oxidation performance

Ethanol oxidation reaction (EOR) is an important energy conversion process. Herein, we have proposed palladium chalcogenide nanosheets to improve C-C bond cleavage ability for EOR. The mass activity of the Te-Pd nanosheets (NSs)/C, which is higher than Se-Pd NSs/C and S-Pd NSs/C (6.9 A mg−1 and 5.3 A mg−1), has achieved 10.0 A mg−1, 12.5-fold higher than commercial Pd/C (0.8 A mg−1) and 8.3 times higher than Pd NSs/C (1.2 A mg−1). The Faradaic efficiency of C1 pathway for EOR on the Te-Pd NSs/C can improve to 56.6% compared with Pd NSs/C (25.7%) at 0.8 VRHE. Density functional theory calculations reveal that the orbital hybridization between Pd and Te weakens the adsorption energy of intermediates and reduces the energy barrier of the rate-determining steps in the C1 pathway. Besides, these palladium chalcogenide NSs can also serve as efficient electrocatalysts for ethylene glycol oxidation reaction and methanol oxidation reaction.

Efficient alcohol electro-oxidation based on a 3D Ni(II)-MOF with centrosymmetric Ni6 cluster

Designing economical and efficient anode catalysts is critical for the commercial use of direct alcohol fuel cells (DAFCs). In this work, a novel Ni(II)-based metal–organic framework (MOF), {[Ni3(μ3-OH)(TMBTI)(1,4-bib)(H3O)}n (H6TMBTI = 2,4,6-trimethylbenzene-1,3,5-triylisophthalate, 1,4-bib = 1,4-bis(1-imidazoly)benzene) (CTGU-38, CTGU = China Three Gorges University), was successfully synthesized through solvothermal method. Structural analyses reveal that the CTGU-38 possesses a unique Ni6(μ3-OH)2(COO)12 cluster and 3D porous framework with a rare (6,16)-connected topology. Further electrochemical experiments demonstrate that the CTGU-38 exhibits good electrocatalytic oxidation performance towards various alcohol fuel molecules, including the methanol oxidation reaction (MOR), ethanol oxidation reaction (EOR), n-propanol oxidation reaction (NPOR), and isopropanol oxidation reaction (IPOR), with peak current densities ranging from 26.9 to 54.46 mA cm−2 in alkaline solution. These results indicate that the CTGU-38 appears to be a potential non-noble metal-based electrocatalyst for DAFCs, and this work provides new insights into the design of more efficient electrocatalysts at the atomic scale for energy conversion.

Facile Synthesis of Multifunctional Ni(OH)2-supported Core-shell Ni@Pd Nanocomposites for the Electro-oxidation of Small Organic Molecules.

In the domain of proton exchange membrane fuel cells (PEMFCs), the development of efficient and durable catalysts for the electro-oxidation of small organic molecules, especially of alcohols (methanol, ethanol, ethylene glycol, et al.) has always been a hot topic. A large number of related electrocatalysts with splendid performance have been designed and synthesized till now, while the preparation processes of most of them are demanding on experimental operations and conditions. Herein, we put forward a facile and handy method for the preparation of multifunctional Ni(OH)2-supported core-shell Ni@Pd nanocomposites (Ni(OH)2/Ni@Pd NCs) with the assistance of galvanic replacement reaction (GRR) at room temperature and ambient pressure. As expected, the Ni(OH)2 substrate can prevent the aggregation of core-shell (CS) Ni@Pd nanoparticles (NPs) and inhibit the formation of COads and further prevent Pd from being poisoned. The synergistic effect between CS Ni@Pd NPs and Ni(OH)2 substrate and the electronic effect between Pd shell and Ni core contribute to the outstanding electrocatalytic performance for methanol, ethanol, and ethylene glycol oxidation in alkaline condition. This study provides a succinct method for the design and preparation of efficient Pd-based electrocatalysts for alcohol electro-oxidation.

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.

Assembly of Alloyed PdM (Ag, Cu, and Sn) Nanosheets and Their Electrocatalytic Oxidation of Ethanol and Methanol.

Direct alcohol fuel cells are popular due to their high energy density, abundant sources, and ease of transportation and storage. Palladium-based nanosheet self-assembled materials have emerged as an effective catalyst for alcohol oxidation reactions. In this work, nanosheets were synthesized with the same feeding ratio assembly of alloyed PdM (M = Ag, Cu, and Sn). The introduction of the second element was able to enhance the catalytic response of the catalysts to alcohol electrooxidation. Among them, the PdCu alloy exhibited the best performance in terms of catalytic activity, toxicity resistance, and stability to ethanol oxidation reaction (EOR) and methanol oxidation reaction (MOR). The catalytic current densities for EOR can reach 2226, 2518, and 1598 mA mg-1 for PdAg, PdCu, and PdSn nanosheet assemblies, respectively. These are mainly attributed to better electronic effects, altered atomic distances within the cell for the d-band centers of Pd, and a larger electrochemical active surface area (ECSA). The optimized d-band center is beneficial to promote the catalytic performance of EOR and MOR. Experimental data also demonstrated that higher electrocatalytic temperature, higher pH, and higher alcohol concentration can accelerate the rate of alcohol electrooxidation. These results have the potential to be extended to Pd-M (M = other metals) nanosheets and help for a wider range of catalytic applications.

Au/Pt Bimetallic Nanowires with Stepped Pt Sites for Enhanced C-C Cleavage in C2+ Alcohol Electro-oxidation Reactions.

Efficient C-C bond cleavage and oxidation of alcohols to CO2 is the key to developing highly efficient alcohol fuel cells for renewable energy applications. In this work, we report the synthesis of core/shell Au/Pt nanowires (NWs) with stepped Pt clusters deposited along the ultrathin (2.3 nm) stepped Au NWs as an active catalyst to effectively oxidize alcohols to CO2. The catalytic oxidation reaction is dependent on the Au/Pt ratios, and the Au1.0/Pt0.2 NWs have the largest percentage (∼75%) of stepped Au/Pt sites and show the highest activity for ethanol electro-oxidation, reaching an unprecedented 196.9 A/mgPt (32.5 A/mgPt+Au). This NW catalyst is also active in catalyzing the oxidation of other primary alcohols, such as methanol, n-propanol, and ethylene glycol. In situ X-ray absorption spectroscopy and infrared spectroscopy are used to characterize the catalyst structure and to identify key reaction intermediates, providing concrete evidence that the synergy between the low-coordinated Pt sites and the stepped Au NWs is essential to catalyze the alcohol oxidation reaction, which is further supported by DFT calculations that the C-C bond cleavage is indeed enhanced on the undercoordinated Pt-Au surface. Our study provides important evidence that a core/shell structure with stepped core/shell sites is essential to enhance electrochemical oxidation of alcohols and will also be central to understanding electro-oxidation reactions and to the future development of highly efficient direct alcohol fuel cells for renewable energy applications.

INFLUÊNCIA DO TEMPO DE SÍNTESE NAS PROPRIEDADES DE HÍBRIDOS PtRu/CARBONO PREPARADOS PELO MÉTODO DA CARBONIZAÇÃO HIDROTÉRMICA

Background: PtRu/C electrocatalysts present good results in methanol electo-oxidation. The activity of these electrocatalysts is strongly dependent on the synthesis method. Additionally, the use of mesoporous carbons or nanostructured carbons increases the performance of electrocatalysts applied in alcohol electro-oxidation. The hydrothermal carbonization method is an alternative to obtain different nanoarchitectures without involving harsh conditions. Aims: Thus, this work aimed to evaluate the influence of synthesis time on the properties of PtRu/Carbon hybrids prepared by the hydrothermal carbonization method. Methods: PtRu/Carbon hybrids were prepared by hydrothermal carbonization at different times of synthesis (6 h and 12 h). It used cellulose as a carbon source and reducing agent and H2PtCl6.6H2O and RuCl3.xH2O as metal sources and catalysts of the carbonization process. The materials were treated at 900 °C and characterized by energy-dispersive X-ray spectroscopy, thermogravimetric analysis, B.E.T isotherms, X-ray diffraction, transmission electron microscope and cyclic voltammetry. The electro-oxidation of methanol was studied by chronoamperometry. Results: The increase in synthesis time from 6 to 12 hours, apparently, resulted in an increase in mean particle size, reduction of mesoporous volume and increase in superficial area and total pore volume. The chronoamperometry of methanol electro-oxidation on these PtRu/Carbon hybrids indicated a higher electroactivity to the material prepared in 6 hours. Discussion: Probably, the higher electroactivity of material prepared in 6 h is associated with smaller particle size, mesoporous structure and surface oxides content. Conclusions: Therefore, it is possible to affirm that the synthesis time is an important parameter that affects the physical-chemical properties of metal/carbon hybrids obtained by the hydrothermal carbonization method.