Electrocatalysis最新文献

Methods for detecting contaminants in drinking water are crucial for protecting public health. Despite manganese (Mn) being an essential mineral for humans, Mn in high concentrations is suspected of being associated with negative cognitive and neurological effects on humans, especially on children. Current methods of detection, though reliable, are limited in the application to real-time easy-to-use, field or bench-top monitoring applications for testing drinking water. Herein, chronoamperometry (CA) is explored to quantitatively analyze manganese samples for drinking water applications. CA proved to be effective at measuring the concentration of Mn²⁺ in water samples with excellent recovery rates (97.8%) and reproducibility between electrodes. With 1-min deposition using bare gold electrodes, CA was able to obtain a detection limit of 34.3 µM. Furthermore, with a 5-min deposition using bare gold electrodes, CA was able to obtain a detection limit of 4.64 µM. This new CA method also offers a simplified cleaning method that will allow electrodes to be used continuously for differing samples or replicate tests. The cleaning procedure permits the reuse of electrodes, while simultaneously eliminating the need for special surface modifications on the electrodes. Ultimately, this cleaning procedure offers a faster and more efficient procedure than previous methods such as polishing. The CA method also demonstrated minimal interference effects when tested with varieties of water hardness, ionic strength, common electroactive species (Cu²⁺, Fe²⁺, Fe³⁺, and Cl⁻), and organic matters in aqueous environments. This CA method is easy to use, requires portable equipment, uses reagents that are easily accessible, and does not require extensive sample preparation.

The oxygen evolution reaction (OER) holds pivotal importance in sustainable energy conversion, as it forms the critical half-reaction in various electrochemical processes, including water splitting for hydrogen production and rechargeable metal-air batteries. Here, a CoFe₂O₄@Co₃O₄ nano-composite was synthesized using a facile hydrothermal process and deposited onto the surface of nickel foam through electrophoresis. Characterization using XRD, Raman spectroscopy, and XPS confirmed the successful synthesis of the composite, exhibiting characteristic peaks of both Co₃O₄ and CoFe₂O₄. The nano-composite exhibited a more amorphous phase than pure oxides, benefiting electrocatalytic activity. Scanning and transmission electron microscopy highlighted the composite’s morphological characteristics, showcasing a Co₃O₄ island distribution on the CoFe₂O₄ surface. Electrochemical evaluations revealed the superior oxygen evolution reaction (OER) performance of CoFe₂O₄@Co₃O₄, with low overpotentials, faster kinetics, and enhanced stability compared to pure oxides and the benchmark RuO₂ catalyst. A comprehensive analysis was carried out to investigate the dynamic behavior during electrocatalytic oxygen evolution reaction. This study unveils the intricate charge and electron transfer mechanisms between cobalt and iron atoms, providing insights into their collaborative role throughout the OER process.

Graphical Abstract

Corrosion has been identified as the primary mechanism causing pipeline failures, leading to significant economic losses and environmental problems. One of the effective and economical methods to prevent metal corrosion is to add corrosion inhibitors. Although environmentally friendly corrosion inhibitors are beneficial to the ecological environment, their lower corrosion inhibition efficiency compared to traditional corrosion inhibitors has limited their application. Therefore, this paper aims to develop an environmentally friendly compound corrosion inhibitor that can meet the practical industrial requirements. The corrosion inhibition effect of two complexes of cystine, namely cystine + sodium molybdate (Cys-Cys + MS) and cystine + zinc gluconate (Cys-Cys + ZG), on pipeline steel in 1 M HCl was investigated. And the synergistic corrosion inhibition mechanism of these two composite corrosion inhibitors was discussed. The results indicated that the corrosion inhibition performance of Cys-Cys + MS and Cys-Cys + ZG complexes was significantly better than that single inhibitors at higher concentration. Furthermore, it was observed that the corrosion inhibition performance of Cys-Cys + ZG was superior to that of Cys-Cys + MS. The maximum corrosion inhibition efficiency of the two compound corrosion inhibitors was achieved at the concentration of (2 + 4) mM.

Graphical Abstract

Electrocatalytic water splitting has received widespread attention due to the slow kinetics of the reaction and the complex electron transfer process, the oxygen evolution reaction (OER) occurring at the anode has become a major obstacle. The improved OER performance is attributed to the significant enhancement in accessible surface active sites and the decrease in charge transfer resistance. The exploration of efficient, cheap, and stable electrocatalysts for OER is of significant importance for energy conversion and storage. Currently, transition metal oxides (TMOs) show enormous potential as electrode materials for OER due to their low cost, redox chemistry, and high chemical stability. In this work, an impregnation method is demonstrated to synthesize Cu-based metal oxides doped with Ni (CuO, Cu_0.9Ni_0.1O, Cu_0.7Ni_0.3O, and Cu_0.5Ni_0.5O/NiO) as high-efficiency and low-energy electrocatalysts for the oxygen evolution reaction under alkaline conditions. This work combines the excellent catalytic efficiency of the transition metal with the large specific surface area and the substantial number of pores of the MOF. All materials show good overpotential values of 359, 352, 346, and 340 mV at a current density of 10 mA cm⁻². The Tafel slopes are 82.5, 47, 65, and 54 mV dec⁻¹, respectively, with very small attenuation for long-term catalytic reactions. Furthermore, the electrocatalysts showed short-term electrochemical stability for 12 h. Therefore, the present method opens a new path for the preparation of efficient and low-cost materials for application in OER.

Graphical Abstract

CO₂ reduction and fixation are one of the most interesting topics in the fields of environmental electrochemistry and electrocatalysis. Many studies on CO₂ electroreduction using various metal electrodes have been reported. However, this reaction requires a high overpotential in general, which lowers the energy conversion efficiency and prevents its practical applications to reduce CO₂ emission to the atmosphere. The use of a membrane electrode assembly (MEA) is expected to be a breakthrough for the CO₂ electroreduction. Particularly, methanation (converting CO₂ into CH₄) with MEAs incorporating Cu-based catalysts attracts special attention as a tool for carbon cycling, thanks to high faradaic efficiencies and relatively high energy conversion efficiencies. Different from Cu, Pt has long been recognized as an inactive catalyst for CO₂ reduction. Contrary to the common consensus, MEAs incorporating a Pt-based electrocatalyst were found very recently to be as active as Cu-based catalysts toward methanation under specific reaction conditions. The high activity of Pt arises from a reaction mechanism different from that for Cu; most likely the Langmuir–Hinshelwood mechanism for Pt and the Eley–Rideal mechanism for Cu. This mini-review discusses CO₂ electrochemical methanation using MEAs as a potential method for carbon capture. The CO₂ reduction to CH₄ using a H₂-CO₂ fuel cell is also presented.

Graphical Abstract

Metal-organic cobalt hydroxide emerges as a cost-effective electrocatalyst for the oxygen evolution reaction (OER) in energy conversion. However, the limited active sites and poor conductivity hinder their large-scale application. This study employed salicylate as a bridging ligand to synthesize iron-incorporated metal-organic cobalt hydroxide. The influence of Fe intercalation on Co(OH)(Hsal) (where Hsal denotes o-HOC₆H₄COO⁻) was investigated using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Fe_0.2Co_0.8(OH)(Hsal) demonstrates remarkable electrocatalytic activity, displaying an OER overpotential of 298 mV at 10 mA cm⁻² and a Tafel slope of 57.46 mV dec⁻¹. This enhancement can be attributed to improved charge transfer kinetics and increased active sites. This work highlights the crucial role of Fe in improving the efficiency of Co-based oxygen-evolving catalysts (OECs) and its potential for boosting efficient hydrogen generation in alkaline environments.

Graphical Abstract

The growing interest in energy demand became an important issue for several sectors like industry and transportation. Recently, fuel cells generated a new solution for global energy deficiency. Therefore, we developed a new catalyst for fuel cell applications that included nickel oxide nanoflower with polyaniline to enhance the electrooxidation of ethanol. The structure of the modified electrode was characterized by X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (IR). At the same time, surface morphology and structural thermal stability were utilized by Scanning electron spectroscopy (SEM) and Thermal gravimetric analysis (TGA), respectively. Otherwise, ethanol electrooxidation was studied by several electrochemistry techniques like cyclic voltammetry (CVs) and chronoamperometry (CA). The activity of the electrocatalyst toward ethanol conversion reached 32 mA cm⁻² at a potential of 0.46 V (vs. Ag/AgCl). The effect of changing the thickness of the conducting polymer was studied to find out the optimum catalysis condition. Several chemical kinetics were calculated, like diffusion coefficient (D), Tafel slope, and transfer coefficient. The long-term stability of the modified electrode for 240 min. Whereas the anodic current decreased by 15% after continuous oxidation of ethanol in an alkaline medium.

Graphical Abstract

Utilizing the density functional theory (DFT) method, we investigated the catalytic activity of N-doped graphene quantum dots (NGQDs) with nitrogen (N) atoms strategically doped at various active sites on the surface. We focused on exploring their efficiency in the 2e⁻ and 4e⁻ reduction pathways for oxygen reduction reaction (ORR). By introducing N-doping at the central benzene ring of carbon-based materials, we observed the formation of localized π-orbitals, significantly enhancing their electrocatalytic activity. In comparison to other reported catalysts, our N-doped GQD metal-free electrocatalyst displayed remarkable adsorption capability. Furthermore, we introduced the hydroxyl group (OH) into the functionalized N-doped GQDs, which further improved electrocatalytic performance. This enhancement was attributed to the decreased HOMO–LUMO energy gap and increased chemical reactivity. The calculated free energy (ΔG) values for each elementary reaction step in the 4e⁻ reduction pathway were highly favorable and indicated the feasibility of the process. Our findings indicate that N-doped GQDs exhibit exceptional activity for the ORR, positioning them as promising carbon-based metal-free electrocatalysts. Consequently, they hold significant potential as an alternative to noble metal-based catalysts in proton exchange membrane fuel cells (PEMFCs) and metal-air batteries.

Graphical Abstract