Electrocatalysis最新文献

In the carbon dioxide reduction reaction (CO₂RR), the direct synthesis of unsaturated heavy hydrocarbons such as α-olefins is more attractive for modern society. However, the underlying reaction mechanism remains unclear because the C–C coupling towards α-olefins is difficult to control. Therefore, in order to improve the selectivity of α-olefins, a tandem catalyst is proposed based on CCFs. After detailed screening and analysis, Fe-Ti-Pc-Mo-S-CCFs composed of Fe-Ti-Pc ligand and MoS₄ node is considered to have high selectivity for CO₂RR and good inhibition of competitive HER, which is attributed to the orbital hybridization mechanism between CO₂ and Fe and Ti. The reaction mechanism and complex intermediates of the synthesis of α-olefins from the CO₂ hydrogenation reaction are systematically investigated, including four pathways. Density functional theory (DFT) simulations indicate that the asymmetric coupling of *CH₂ and *COOH forms *CH₂COOH, followed by the continuous insertion of CH₂, leading to the formation of α-olefins. This mechanism is the optimal pathway for CO₂RR. In addition, the competitiveness of C–C coupling and proton-coupled electron transfer (PCET) reactions are also discussed. The results conclude that C₁-C₂ and C₁-C₃ couplings are more advantageous. In this work, the results reveal that Fe-Ti-Pc-Mo-S-CCFs has the stability, high selectivity, and high conductivity, enables CO₂ reduction to a high-value product, and provides a novel possibility for the design of electrocatalysts for CO₂RR.

Graphical Abstract

Effective and sustainable electrocatalytic reduction of nitrate is greatly desired to solve the problem of global water contamination and provide a promising way to generate fossil-free ammonia. In this regard, Pt-Fe₃O₄ nanoparticles are decorated on Ni foam (NF) using the hydrothermal method to achieve Pt-Fe₃O₄/NF nanocomposite electrocatalyst. Various characterization techniques investigate the structural and morphological properties of Pt-Fe₃O₄/NF nanocomposite. Benefiting from the small size of Pt and Fe nanoparticles, the Pt-Fe₃O₄/NF nanocomposite reveals excellent performance for electrocatalytic nitrate reduction with an NH₄⁺ yield rate of 0.301 mmol h⁻¹ cm⁻² (5.418 mg h⁻¹ mg⁻¹_cat.) and Faradaic efficiency of 80.7% at − 0.8 V vs. RHE. Pt-Fe₃O₄/NF nanocomposite exhibits unique metallic properties and abundant surface sites due to a synergistic effect of Pt-Fe nanostructure favorable for the electrochemical and hydrogenation reduction processes. Moreover, Pt-Fe₃O₄/NF nanocomposite reveals outstanding long-term stability and durability. Isotope labeling experiments are performed, and results demonstrate that ammonia originates from nitrate reduction. These favorable outcomes of Pt-Fe₃O₄/NF nanocomposite emphasize its potential for treating nitrate wastewater for ammonia recovery and prospects for its industrial applications.

Graphical Abstract

An efficient electrocatalyst was prepared by fabricating Pt-Fe₃O₄ on NF using hydrothermal method for electrochemical nitrate reduction to ammonia. Pt-Fe₃O₄/NF showed a remarkable NH₄⁺ yield rate with high Faradaic efficiency at − 0.8 V vs. RHE. Also, the Pt-Fe₃O₄/NF nanocomposite exhibited outstanding stability and durability.

Polymeric carbon nitrides (C₃N₄) are photochemically active organic semiconductors that can be produced in a wide range of structural types. Here, a poly-(heptazine imide) containing nickel single atoms (Ni-PHI) is employed for photochemical hydrogen production and is compared to the non-nickel-doped semiconductor. Film deposits are formed on a platinum disk electrode (to detect hydrogen) and a coating of the molecularly rigid polymer of intrinsic microporosity PIM-1 is applied to (i) mechanically stabilize the photo-catalyst film without impeding photocatalysis and (ii) assist in the interfacial hydrogen capture/oxygen suppression process. In the presence of hole quenchers such as methanol or ethanol, anodic photocurrents linked to hydrogen production/oxidation are observed. A comparison with an experiment on glassy carbon confirms the formation of interfacial hydrogen as a mediator. The effects of hole quencher concentration are evaluated. The system Pt/Ni-PHI/PIM-1 is employed in a single-compartment photo-fuel cell.

Graphical Abstract

Here, a general method for fabricating active electrocatalysts is introduced for oxygen evolution reaction (OER) based on multimetallic (ternary alloy) structures formed on the N-doped nanoporous carbon platform without using ruthenium or iridium. Accordingly, three different sizes, small, medium, and large, of cobalt zeolitic imidazolate framework-67 (ZIF67X, X: S, M, L) are synthesized. Then, the product is carbonized via direct pyrolysis at 800 °C in an argon atmosphere to yield nitrogen-doped nanoporous carbon composited with cobalt nanoparticles (PZIF67X₈₀₀). To improve the activity, the most active nanoporous system for OER (PZIF67L₈₀₀) is further modified by electrochemical deposition of Co, Ni, and Fe (PZIF67L₈₀₀-CoNiFe). The electrochemical results revealed a large electrocatalytic activity for the GC-PZIF67L₈₀₀-CoNiFe toward the OER in alkaline media, Tafel slopes of 72 mV dec⁻¹ and overpotentials of 314 mV at 30 mA cm⁻² (η₃₀), compared with those obtained under the same conditions on GC-RuO₂ (99 mV dec⁻¹ and 499 mV). The improved activity is attributed to (i) the increase in active surface area and simultaneous formation of Co nanoparticles and nitrogen-doped porous carbon, causing uniformly dispersed metal nanoparticles in the composite, and (ii) synergistic effect between the ingredients of ternary alloy nanoparticles (CoNiFe-NPs) and nitrogen-doped carbon nanoporous platform.

Graphical Abstract

Developing excellent electrocatalysts is a significant step in accelerating the widespread implementation of the electrochemical hydrogen evolution reaction (HER). MoS₂ is one of the promising alternatives to platinum-based catalysts, while its HER activity is far from Pt due to the lack of active sites. It is urgent to develop a novel strategy to activate the basal planes of MoS₂ for enhancing the HER activity. Herein, a facile hydrothermal method with a low-temperature H₂O₂ etching method is developed to fabricate MoS₂ with O-doped and S-vacancy dual defects. The dual defects MoS₂ nanosheet demonstrates remarkable hydrogen evolution reaction (HER) activity, achieving 10 mA cm⁻² with a small overpotential of around 143 mV in 0.5 M H₂SO₄.

Graphical Abstract

Construct dual-defect MoS2 via a facile hydrothermal method and mild H2O2 etching process.

To detect the dengue virus NS1 protein with high sensitivity, this research suggests an electrochemical immunosensor based on the Al-TCPP adsorption aggregation signal amplification approach. We created a type of metal-organic framework (MOF) material called astrophytum myriostigma, which resembles a cactus plant and has a large specific surface area. In addition, it can produce electrostatic attraction with the amino groups on methylene blue (MB), firmly fix MB on the MOF material, and manage MB reunion after adsorption, which is helpful for electron transmission and amplifies the electrical signal. The cationic dye methylene blue has redox characteristics. It possesses a high electron transfer rate, electrochemical reversibility, and strong biocompatibility. The generated electrochemical immunosensor has good reproducibility and stability, and the relationship between the analyte concentration and electrical signal strength is linear. The suggested immunosensor has a broad detection range from 10 fg/mL to 100 ng/mL with a low detection limit of 9.12 fg/mL under ideal conditions.

Graphical Abstract

In this work, hierarchical Cu₂ZnSnS₄ electrocatalysts with different morphologies and stoichiometries were synthesized via the hydrothermal method and their electrocatalytic performances in hydrogen evolution reaction were evaluated. The morphologies of Cu₂ZnSnS₄ electrocatalysts were modulated by adjusting the content of surfactants during the hydrothermal process. The stoichiometries of as-prepared Cu₂ZnSnS₄ were found to be Cu₂Zn_0.8Sn_0.7S_2.9, Cu₂Zn_0.7Sn_1.2S_4.7 and Cu₂Zn_0.5Sn_0.7S_3.2 for the absence of surfactant and the addition of polyethylene glycol-(400) (PEG 400) and octylphenol polyoxyethyleneether-10 (OP 10) respectively. The Cu₂ZnSnS₄ synthesized with the addition of PEG 400 displayed superior electrocatalytic activity in acid medium with an overpotential of 295 mV obtained at 10 mA cm^− 2 and a Tafel slope of 133 mV dec^− 1. This work reveals that the stoichiometry and microstructure of Cu₂ZnSnS₄ are critically important for its electrocatalytic activity while have less impact on the electrocatalytic durability, and provides useful information to explore the utilization of chalcogenides as the attractive electrocatalysts.

Efficient and cost-effective electrolysis technique is prerequisite for industrial scale hydrogen production. This study demonstrates fabrication of electrochemical catalyst in the form of a composite structure generated through rapid oxidation using microwave (MW) of self-assembled IrO₂ nanoparticles on reduced graphene oxide (rGO). MW-IrO₂/rGO catalysts were synthesized using the microwave-assisted aqueous solution method, and its physical/chemical structure, morphology, and oxygen evolution reaction (OER) properties were evaluated depending on the power of microwave. The composite structure with rGO support and small particle size of IrO₂ allow homogeneous dispersion, and large adsorption area, which dramatically enhances the electron and proton transports. The increased electrochemical surface area resulted in excellent performance of OER. Moreover, this study suggests a simple catalyst preparation method, leading to acceleration of manufacturing speed and cost saving. Thus, this work provides new insights into a facile microwave-assisted rapid oxidation method for efficient electrochemical applications such as PEM electrolysis cells.

Graphical Abstract

A series of Pd/Fe₃O₄@S-rGO was synthesized under various deposition times of Pd and their catalytic activity was investigated in alkaline media via chronoamperometry (CA), cyclic voltammetry (CVs), and electrochemical impedance spectroscopy (EIS) for the methanol oxidation reaction. For the S source, sodium dodecylbenzene sulfonate (SDBS) was used to obtain ultrafine Fe₃O₄ particles and enhance the graphene layer properties. Through the characterization measurements, it is concluded that Pd was deposited successfully onto Fe₃O₄@S-rGO (S and Fe₃O₄ dual-doped reduced graphene oxide) with nanoscale cubic lattice nanostructure. In the presence of Fe₃O₄, the band gap of Pd₄₅₀/ITO decreased from 3.46 to 1.74 eV. The band gap of fabricated catalyzes changed with the deposition time of Pd. In addition, the synergistic effect between Pd and Fe₃O₄ enhances the catalytic activity of the electrode toward methanol oxidation when compared bulk Pd electrode. The Pd₄₅₀/Fe₃O₄@S-rGO electrocatalyst showed a current density of 22.3 mA cm⁻² at a scan rate of 30 mV s⁻¹ with remarkable long-term stability in 0.5 M methanol in 1 M NaOH. This value is 2.2 times higher than the Pt/C (10 mAcm⁻²) catalyst under the same conditions. With modifying Fe₃O₄ the Tafel slope of Pd₄₅₀/ITO decreased from 180 to 118 mVdec⁻¹.

Graphical Abstract