Electrocatalytic Oxidation Reaction Research Articles

Multimetallic Metasurfaces for Enhanced Electrocatalytic Oxidations in Direct Alcohol Fuel Cells

AbstractPlasmonic metasurfaces enable unprecedented manipulation of light by using periodic arrangement of resonant unit cells or nanoantennas. Here, multimetallic metasurfaces made of self‐standing Ni/Au‐Pt nanostructured films are shown to significantly enhance an electrocatalytic oxidation reaction employed in direct alcohol fuel cells. The Ni/Au metasurfaces support photonic and plasmonic modes, which are leveraged for the site‐selective deposition of Pt electrocatalysts within the electromagnetic hot spots, where their reactivity can be strongly increased. The enhanced electrocatalytic activity for the methanol oxidation reaction (MOR) is primarily attributed to electronic effects due to the excitation of hot charge carriers and plasmonic near fields, as supported by electromagnetic simulations and kinetic isotopic experiments. Wavelength‐dependent photoelectrochemical investigations suggest that Ni/Au‐Pt metasurfaces enhances MOR over a broad spectral range and favors different light‐induced reaction mechanisms depending on the selected energy window.

Electrochemically reduced graphene oxide/Cu-MOF/Pt nanoparticles composites as a high-performance sensing platform for sensitive detection of tetracycline.

Apromising sensing platform was constructed based on an electrochemically reduced graphene oxide (ErGO)/copper metal-organic framework (Cu-MOF)/platinum nanoparticles (ErGO/Cu-MOF/PtNPs) modified glassy carbon electrode for the detection of tetracycline. The ErGO/Cu-MOF/PtNPs composite electrode possessed an excellent electrochemical performance to tetracycline detection mainly due to the synergistic effect of ErGO, Cu-MOF and PtNPs. Theelectrochemical kinetics and catalytical mechanism of tetracycline were systematically studied, showing that tetracycline's electrocatalytic oxidation reaction was an absorption-controlled two-step process involving two electrons and one proton transfer, respectively. Low concentration of tetracycline was detected by amperometry with the a linear range of 1 ~ 200μM (R2 = 0.9900) and adetection limit of 0.03μM (S/R = 3). The proposed sensor was successfully applied tothe detection of tetracycline in the real water samples with recoveries of 93.5% ~ 106%, and relative standard deviations (RSD) of 4.65% ~ 5.21% (n = 3). Furthermore, acceptable stability, repeatability and reproducibility were verified for continuous determination of tetracycline under optimized conditions. The ErGO/Cu-MOF/PtNPs composite electrode also demonstrated better anti-interference performance compared to other types of antibiotics than that of similar structural tetracyclines. Therefore, the proposed ErGO/Cu-MOF/PtNPs composites might provide a potential sensing platform for detecting analogous tetracyclines or total tetracyclines in the environment.

Branch-Regulated Palladium-Antimony Nanoparticles Boost Ethanol Electro-oxidation to Acetate.

Tuning the composition and morphology of bimetallic nanoparticles (NPs) offers an effective strategy to improve their electrocatalytic performance. In this work, we present a facile wet-chemistry procedure to engineer PdSb NPs with controlled morphology. Spherical or branched NPs are produced by tuning the heterogeneous nucleation of Sb on Pd seeds. Compared with pure Pd NPs, the incorporation of Sb not only decreases the amount of Pd used but also results in a significant increase of activity and stability for the electrocatalytic ethanol oxidation reaction (EOR). Best performances are obtained with highly branched PdSb NPs, which deliver a specific activity of 109 mA cm-2 and a mass activity of up to 2.42 A mgPd-1, well above that of a commercial Pd/C catalyst and branched Pd NPs. Moreover, PdSb displays significant stability enhancement of over 10 h for the EOR measurements. Density functional theory calculations reveal that the improved performance of PdSb NPs is related to the role played by Sb in reducing the energy barrier of the EOR rate-limiting step. Interestingly, as a side and value-added product of the EOR, acetate is obtained with 100% selectivity on PdSb catalysts.

Optimizing local charge distribution of metal nodes in bimetallic metal–organic frameworks for efficient urea oxidation reaction

A significantly lower voltage was required in NiFe-MIL-53-NH 2 when using full urea electrolysis instead of overall water splitting. • Incorporating Fe induces the formation of electrophilic Ni 3+ and nucleophilic Fe 3+ . • The bimetallic NiFe-MIL-53-NH 2 presents excellent electrocatalytic UOR activity. • This work provides a new strategy to explore effective UOR electrocatalysts. Electrocatalytic urea oxidation reaction (UOR) presents lower thermodynamic potential than oxygen evolution reaction (OER), thus exhibiting promising potential to enhance the efficiency of overall water splitting. However, due to the intrinsically sluggish six-electron transfer process, the efficiency of UOR is still not satisfied. In response, we synthesized a bimetallic NiFe-MIL-53-NH 2 with superior activity toward UOR, which only needs a low potential of 1.398 V vs. RHE to obtain 50 mA cm −2 in 1.0 M KOH with 0.33 M urea, much lower than that in 1.0 M KOH (1.721 V vs. RHE). Furthermore, NiFe-MIL-53-NH 2 presents significantly more excellent UOR activity compared to its monometallic counterparts. The TOF value in NiFe-MIL-53-NH 2 (0.16 s −1 ) at 1.4 V vs. RHE is about 133- and 246-folds higher than that Ni-MIL-53-NH 2 (1.2 × 10 -3 s −1 ) and Fe-MIL-53-NH 2 (6.5 × 10 -4 s −1 ), respectively. XPS characterization discloses that the incorporation of Fe into Ni-MIL-53-NH 2 framework optimizes the local charge distribution of metal nodes, leading to the formation of electrophilic Ni 3+ and nucleophilic Fe 3+ species, which can absorb electron-donating –NH 2 and electron-withdrawing C = O groups in urea, respectively, and therefore result in excellent UOR. This simple strategy of regulating local charge distribution of active species by fabricating bimetallic MOFs provides a new strategy and direction to explore other highly efficient UOR electrocatalysts.

Electrocatalytic selective oxidation of ethylene glycol: A concise review of catalyst development and reaction mechanism with comparison to thermocatalytic oxidation process

As an important water and seawater degradable plastic monomer, glycolic acid can be synthesized by selective oxidation of ethylene glycol. This review recapitulates recent advances in electrocatalytic ethylene glycol oxidation reaction (EGOR) from the aspects of catalytic performance and reaction mechanism. For catalytic performance evaluation, target product yield and space-time yield are correlated and analyzed for electrocatalytic and thermocatalytic EGOR systems. To elucidate the rationale behind the electrocatalytic selective oxidation of ethylene glycol, previous works using in situ Fourier transform infrared spectroscopy, online differential electrochemical mass spectrometry, ion chromatography, and theoretical calculations to investigate EGOR are systematically reviewed. Finally, the advantages of electrocatalytic EGOR are summarized by comparing electrocatalytic and thermocatalytic processes.

Few-layered black phosphorus/cucurbit[6]uril as a Pd catalyst support for photo-assisted electrocatalytic ethanol oxidation reaction

In this work, macrocyclic molecule cucurbit[6]uril (CB[6])-modified two-dimensional black phosphorus nanosheets (BPNSs) used as photoactivated support were synthesized by a simple solvothermal method. Palladium nanoparticles were anchored on the surface of BP-CB[6] to obtain the composite material Pd/BP-CB[6] by using a chemical reduction method. Then, the electrocatalytic activity of the composite material modified electrode in the ethanol oxidation reaction (EOR) was investigated. The Pd/BP-CB[6] catalyst exhibits a high mass activity (1420 mA·mgPd−1), which is 4.1 times higher than commercial Pd/C. Impressively, the ethanol oxidation activity of the Pd/BP-CB[6] electrode under visible light irradiation (1900 mA·mgPd−1) is 1.34 times higher than under dark conditions. The result is obtained through a series of evaluations, including cyclic voltammetry, chronopotentiometry, chronoamperometry, and electrochemical impedance spectroscopy, in which the prepared Pd/BP-CB[6] shows higher catalytic activity and stability than Pd/BP. These results suggest that the synergistic effect of photocatalysis and electrocatalysis improves the electron transport kinetics of the Pd/BP-CB[6] electrode in the EOR process. Two-dimensional black phosphorus nanosheets can be used as promising photoactivated supports, to which functional material CB[6] is fixed by hydrogen bonding. Meanwhile, the electrostatic interaction between CB[6] and noble metal helps to improve the stability of the catalyst. This work provides a new idea for developing efficient photoresponsive electrode material in direct ethanol fuel cells.

Facile in Situ Transformation of NiOOH into MOF-74(Ni)/NiO OH Heterogeneous Composite for Enchancing Electrocatalytic Methanol Oxidation.

A new MOF-74(Ni)/NiOOH heterogeneous composite was synthesized via NiOOH microsphere precursor. The electrocatalytic methanol oxidation reactions’ (MOR) performance was assessed. The as-prepared MOF-74(Ni)/NiOOH exhibited excellent activity with high peak current density (27.62 mA·cm−2) and high mass activity (243.8 mA·mg−1). The enhanced activity could be a result of the synergistic effect of the MOF-74(Ni)/NiOOH heterocomposite providing more exposed active sites, a beneficial diffusion path between the catalyst surface and electrolyte, and improved conductivity, favorable for improving MOR performance.

Phase and crystallinity regulations of Ni(OH)2 by vanadium doping boost electrocatalytic urea oxidation reaction

Direct urea fuel cell (DUFC) and overall urea splitting system have attracted considerable attention as promising choice for energy conversion. Whereas, the anodic half reaction of electrocatalytic urea oxidation reaction (UOR) in these systems awfully limited their practical application due to the complex 6-electron transfer process. Herein, vanadium doped nickel (V-Ni(OH)2) with highly efficient electrocatalytic activity toward UOR was developed by a simple coprecipitation method. The introducing of V not only promotes the phase transforming from inactive β-Ni(OH)2 to highly active α-Ni(OH)2, but also simultaneously modulates the electron environment of Ni, facilitating high valence species Ni3+ generation in low overpotential, enhancing the electrocatalytic activity potent of each Ni3+ site and speeding up the electrocatalytic reaction. The optimal V-Ni(OH)2 catalyst exhibits a summit current density of 241 mA cm−2 at 1.6 V vs. RHE, a Tafel slope of 32.15 mV dec-1, outperforming β-Ni(OH)2 and most catalysts that tested on glassy carbon electrode. Furthermore, the assembled direct urea hydrogen peroxide fuel cell (DUPFC) offers a maximum power density of 13.4 mW cm−2 at 20 °C. This work provides an example of combing phase-regulation and electron modulation method for effective UOR electrocatalysts design.

Atomic-precision Pt6 nanoclusters for enhanced hydrogen electro-oxidation

The discord between the insufficient abundance and the excellent electrocatalytic activity of Pt urgently requires its atomic-level engineering for minimal Pt dosage yet maximized electrocatalytic performance. Here we report the design of ultrasmall triphenylphosphine-stabilized Pt6 nanoclusters for electrocatalytic hydrogen oxidation reaction in alkaline solution. Benefiting from the self-optimized ligand effect and atomic-precision structure, the nanocluster electrocatalyst demonstrates a high mass activity, a high stability, and outperforms both Pt single atoms and Pt nanoparticle analogues, uncovering an unexpected size optimization principle for designing Pt electrocatalysts. Moreover, the nanocluster electrocatalyst delivers a high CO-tolerant ability that conventional Pt/C catalyst lacks. Theoretical calculations confirm that the enhanced electrocatalytic performance is attributable to the bifold effects of the triphenylphosphine ligand, which can not only tune the formation of atomically precise platinum nanoclusters, but also shift the d-band center of Pt atoms for favorable adsorption kinetics of *H, *OH, and CO.

Noble-Metal-Free WO3-Decorated Carbon Nanotubes with Strong W–C Bonds for Boosting an Electrocatalytic Glucose Oxidation Reaction

Noble-Metal-Free WO₃-Decorated Carbon Nanotubes with Strong W–C Bonds for Boosting an Electrocatalytic Glucose Oxidation Reaction

Structure‐Performance Relationship of LaFe1‐xCoxO3Electrocatalysts for Oxygen Evolution, Isopropanol Oxidation, and Glycerol Oxidation

AbstractMitigating high energy costs related to sustainable H2production via water electrolysis is important to make this process commercially viable. Possible approaches are the investigation of low‐cost, highly active oxygen evolution reaction (OER) catalysts and the exploration of alternative anode reactions, such as the electrocatalytic isopropanol oxidation reaction (iPOR) or the glycerol oxidation reaction (GOR), offering the possibility of simultaneously lowering the anodic overpotential and generating value‐added products. A suitable class of catalysts are non‐noble metal‐based perovskites with the general formula ABO3, featuring rare‐earth metal cations at the A‐ and transition metals at the B‐site. We synthesised a series of LaFe1‐xCoxO3materials with x=0–0.70 by automated co‐precipitation at constant pH and subsequent calcination at 800 °C. X‐ray diffraction studies revealed that the phase purity was preserved in samples with x≤0.3. The activity towards the OER, iPOR, and GOR was investigated by rotating disk electrode voltammetry, showing a relation between structure and metal composition with the activity trends observed for the three reactions. Additionally, GOR product analysis via high‐performance liquid chromatography (HPLC) was conducted after 24 and 48 h electrolysis in a circular flow‐through cell setup, pointing out a trade‐off between activity and selectivity.

Electrochemical Synthesis of Nitric Acid from Nitrogen Oxidation.

Nitric acid is widely applied in agriculture and industry. The present manufacturing process via a combination of the Haber-Bosch process and the Ostwald oxidation process is accompanied by massive energy consumption and greenhouse gas emissions. The direct electrocatalytic nitrogen oxidation reaction (NOR) to nitric acid is a promising alternative, especially when it is driven by renewable energy sources. The standardization of performance evaluation is the prerequisite for the design and synthesis of efficient electrocatalysts for NOR. In this context, this Minireview first discusses the history of the development of HNO3 manufacturing and the possible reaction mechanisms for electrocatalytic NOR. Then, a strict protocol for electrochemical NOR experiments is recommended. Finally, general research targets associated with techno-economic analysis, challenges, and prospects for NOR are summarized for future studies.

Electrochemical Synthesis of Nitric Acid from Nitrogen Oxidation

AbstractNitric acid is widely applied in agriculture and industry. The present manufacturing process via a combination of the Haber–Bosch process and the Ostwald oxidation process is accompanied by massive energy consumption and greenhouse gas emissions. The direct electrocatalytic nitrogen oxidation reaction (NOR) to nitric acid is a promising alternative, especially when it is driven by renewable energy sources. The standardization of performance evaluation is the prerequisite for the design and synthesis of efficient electrocatalysts for NOR. In this context, this Minireview first discusses the history of the development of HNO3manufacturing and the possible reaction mechanisms for electrocatalytic NOR. Then, a strict protocol for electrochemical NOR experiments is recommended. Finally, general research targets associated with techno‐economic analysis, challenges, and prospects for NOR are summarized for future studies.

Iridium‐based electrocatalysts toward sustainable energy conversion

AbstractElectrocatalysis is an important branch in electrochemistry and also has a significant position in energy storage/conversion. Iridium (Ir)‐based electrocatalysts show promise because of the inherent redox property. Considering the abundance and expensive cost of such noble metal, significant efforts have been made to rationally improve the electrochemical performance of Ir‐based electrocatalysts during these years from the viewpoints of structural design and kinetic analysis. Most of the reports may aim to achieve high Ir atomic utilization with more exposed active sites, and both high electrochemical activity and durable stability are expected. In this case, Ir‐based single atoms, nanostructures, and composites are reported with various electrocatalytic applications of water splitting (involving hydrogen evolution and oxygen evolution reaction) and other electrocatalytic oxidation reactions (involving hydrogen oxidation reaction, methanol oxidation reaction, ammonia oxidation reaction, and formic acid oxidation reaction) as well as other electrocatalytic reduction reactions (involving oxygen reduction reaction, carbon dioxide reduction reaction, and nitrogen reduction reaction). These works deserve to be discussed and this review article comprehensively summarized the most significant reports. We analyzed Ir‐based electrocatalysts from the viewpoints of synthesis, structure, electrochemical property, and reaction mechanism. The challenges and outlooks in the future were also provided from the aspects of fundamental studies and industrial applications, which may attract more attention and provide new insight into the design of advanced Ir‐based electrocatalysts with high performance.image

Manganese-doped molybdenum oxide boosts catalytic performance of electrocatalytic wet air oxidation at ambient temperature

Mn-doping strategy was adopted to modify the structure of MoO2 for enhancing its catalytic activity towards room-temperature electrocatalytic wet air oxidation (ECWAO) reaction. A series of Mn-doped MoO2 were prepared on carbon support, and their structures were investigated to elucidate the productive effect of Mn doping on the catalytic activity of MoO2. The incorporation of MnIII/MnII into the MoO2 lattice induced the transformation from MoIV to MoV and created more oxygen vacancies. Such structural modifications promoted the electron transfer of MoO2 through the redox couples between MoVI/MoV/MoIV and MnIII/MnII, and facilitated the transformation from O2 to adsorbed oxygen species on MoO2 surface. As a result, the ECWAO catalytic activities of Mn-doped MoO2/graphite felt (MoO2/GF) outperformed the activity of MoO2/GF. Among the synthesized series, Mn0.066:MoO2/GF exhibited the highest activity with the maximum turnover frequency (TOF) promoted by 59% than the undoped MoO2/GF. Under the catalysis of Mn0.066:MoO2/GF, the ECWAO process obtains mineralization efficiencies generally above 85% in degrading typical pharmaceutics and person care products (PPCPs). These findings are anticipated to open up a new venue in the design and fabrication of highly active catalysts for air oxidation reactions by using the strategy of selective dopant-induced structure modification.

Porous palladium phosphide nanotubes for formic acid electrooxidation

AbstractThe development of an efficient catalyst for formic acid electrocatalytic oxidation reaction (FAEOR) is of great significance to accelerate the commercial application of direct formic acid fuel cells (DFAFC). Herein, palladium phosphide (PdxPy) porous nanotubes (PNTs) with different phosphide content (i.e., Pd3P and Pd5P2) are prepared by combining the self‐template reduction method of dimethylglyoxime‐Pd(II) complex nanorods and succedent phosphating treatment. During the reduction process, the self‐removal of the template and the continual inside–outside Ostwald ripening phenomenon are responsible for the generation of the one‐dimensional hollow and porous architecture. On the basis of the unique synthetic procedure and structural advantages, Pd3P PNTs with optimized phosphide content show outstanding electroactivity and stability for FAEOR. Importantly, the strong electronic effect between Pd and P promotes the direct pathway of FAEOR and inhibits the occurrence of the formic acid decomposition reaction, which effectively enhances the FAEOR electroactivity of Pd3P PNTs. In view of the facial synthesis, excellent electroactivity, high stability, and unordinary selectivity, Pd3P PNTs have the potential to be an efficient anode electrocatalyst for DFAFC.

Electro-Oxidation Reaction of Methanol over La2–xSrxNiO4+δ Ruddlesden–Popper Oxides

How materials’ crystalline structure influences the underlying electronic configuration, along with redox properties, and plays a pivotal role in electrocatalysis is an intriguing question. Here, solution combustion-synthesized La2–xSrxNiO4+δ (x = 0–0.8) Ruddlesden–Popper (RP) oxides were explored for an electrocatalytic methanol oxidation reaction. Optimal doping of bivalent Sr2+ in the A site enabled the tetragonal distortion and oxidation of Ni2+ to Ni3+ that resulted ultimately in enhanced covalent hybridization of Ni 3d–O 2p with a closer proximity of the O 2p band to the Fermi level. The RP oxide La1.4Sr0.6NiO4+δ exhibited the highest methanol oxidation reactivity vis-à-vis the formation of HCO2H. The proposed mechanism over La1.4Sr0.6NiO4+δ considers a lattice oxygen-mediated methanol oxidation reaction, owing to Fermi-level “pinning” at the top of the O 2p band, which facilitated lattice oxygen atoms prone to oxidation. A high surface concentration of the key active species of Ni–OOH was observed to form during the methanol oxidation reaction with the help of lattice oxygen atoms and oxygen vacancies in La1.4Sr0.6NiO4+δ. The present study offers a uniquely comprehensive exploration of structural and surface properties of RP oxides toward methanol oxidation reactions.

Boosting Electrocatalytic Hydrazine Oxidation Reaction on High-Index Faceted Au Concave Trioctahedral Nanocrystals

Boosting Electrocatalytic Hydrazine Oxidation Reaction on High-Index Faceted Au Concave Trioctahedral Nanocrystals

From inert to active: a cocktail-like mediation of an Ag/Ni mixture for electrocatalytic ammonia oxidation reaction.

We report a highly selective electrocatalytic ammonia oxidation reaction (EAOR) induced by handmilling inert powders of silver (NH3 adsorber) and nickel (OH- adsorber and active site). This cocktail-like mediation provides a good model for mechanistic understanding of the EAOR, benefiting the development of effective non-noble metal catalysts for the EAOR.

A high-performance electrochemical sensor for sensitive detection of tetracycline based on a Zr-UiO-66/MWCNTs/AuNPs composite electrode.

Herein, a high-performance electrochemical sensor was constructed based on a metal-organic framework (Zr-UiO-66)/multi-carbon nanotubes/gold nanoparticles (Zr-UiO-66/MWCNTs/AuNPs) composite modified glassy carbon electrode for sensitive determination of tetracycline. The morphology, structure, and performance of Zr-UiO-66/MWCNTs/AuNPs were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), and electrochemical techniques. The Zr-UiO-66/MWCNTs/AuNPs nanohybrids exhibited excellent electrocatalytic activity towards the oxidation of tetracycline, mainly because of the synergistic effect of the MOFs, MWCNTs, and gold nanoparticles. The electrochemical kinetics and catalytical mechanism of tetracycline were demonstrated, proving that tetracycline's electrocatalytic oxidation reaction was an absorption-controlled two-step process involving the transfer of two protons and two electrons, respectively. Furthermore, a simple and facile method was used to achieve the regeneration of the absorbed saturated electrode. A low concentration of tetracycline was detected by amperometry with the linear ranges of 5 × 10-7 to 2.25 × 10-4 mol L-1 (R2 = 0.9941), the sensitivity was 45.4 mA L mol-1, and the limit of detection was as low as 1.67 × 10-7 mol L-1 (S/N = 3). In addition, the composite electrode demonstrated high selectivity (interference deviation of ± 5%), satisfactory reproductivity (RSD of 5.31%), and long-term stability (easy regeneration) and was successfully applied in the analysis of tetracycline antibiotics in actual samples. Thus, the proposed electrode provides a promising and prospective MOFs-based sensing platform for the detection of tetracyclines in the environment.