Design of best performing hexagonal shaped Ag@CoS/rGO nanocomposite electrode material for electrochemical supercapacitor application

The mixed metal/metal sulphide (Ag@CoS) with reduced graphene oxide (rGO) nanocomposite (Ag@CoS/rGO) was synthesized for the possible electrode in supercapacitors. Ag@CoS was successfully deposited on the rGO nanosheets by hydrothermal method, implying the growth of 2D Ag and CoS-based hexagonal-like structure on the rGO framework. The synthesized nanocomposite was subjected to structural, morphological and electrochemical studies. The XRD results show that the prepared nanocomposite material exhibits a combination of hexagonal and cubic phase due to the presence of CoS and Ag phases together. The band appearing at nearly 470.33 cm⁻¹ in FTIR spectra can be ascribed to the absorption of S–S bond in the Ag@CoS/rGO nanocomposite. The clear hexagonal structure was analysed by SEM and TEM with the grain sizes ranging from nanometer to micrometer. The electrode material exhibits excellent cyclic stability with a specific capacitance of 1580 F/g at a current density of 0.5 A/g without any loss of capacitive retention even after 1000 cycles. Based on the electrochemical performance, it can be inferred that the prepared novel nanocomposite material is very suitable for using as an electrode for electrochemical supercapacitor applications.     

Electrochemical reduction of CO2: Two- or three-electrode configuration

Electrocatalytical conversion of CO₂ into various chemicals like hydrocarbons and CO is regarded as a promising approach to mitigate carbon emission and, meanwhile, to provide sustainable energy and value-added chemicals. Two different reactors are used in this work. One is based upon the two-electrode configuration powered by a DC power supply or Si solar cell, which is suitable for practical applications. Another is three-electrode one powered by a potentiostat, which is feasible to study the electrode performance. Polycrystalline Cu electrode is used as the cathode, and hematite is the anode. Performance of CO₂ reduction using the two- and three-electrode configurations is studied by measuring electrode potential, cell voltage, current density, Faradaic efficiency, and reduction selectivity of CO₂. Cu cathode used here exhibits a low overpotential for CO₂ reduction, specifically for the cell with two-electrode configuration. No obvious difference can be observed between the two types of configurations at a low bias like −0.3 and −0.4 V; while the reactor with two-electrode configuration exhibits better performance at a high bias like −0.8 V than the one with three-electrode configuration. Thus, the reactors with two-electrode configuration are desirable for practical applications, specifically considering solar cells can be used as the power source to provide green and sustainable energy.     

A two-dimensional material for high capacity supercapacitors: S-doped graphene

In this work, sulfur-doped graphene-coated electrodes are prepared by cyclic voltammetry in different potential ranges and different cycles (from 10 to 50) for selective modification of electrodes by different functional groups. The prepared electrodes are characterized by spectroscopic, microscopic and electrochemical methods. In scanning electron microscopic analysis, formation of graphene layers and their porous structure have been determined. Electrochemical impedance spectroscopic and cyclic voltammetric analyses are also used in electrochemical characterization of the electrodes. Then, the prepared sulfur-doped graphene-coated electrodes by using cyclic voltammetry in one-step and low cost are used as electrode materials of supercapacitor for the first time in the literature. Since the mesoporous structure of the electrodes prepared in lower potential ranges increases, specific capacitance of the electrodes increases from 74 to 1833 mF cm⁻² with 10 mA cm⁻² current density. This result shows that specific capacitances of prepared electrodes are higher than those of the electrodes prepared with metal-doped in the literature.     

High-performance counter electrode based on nitrogen-doped porous carbon nanoribbons for quantum dot-sensitized solar cells

Nitrogen-doped porous carbon nanoribbons (NPCNs) are facilely prepared by carbonization of polypyrrole (PPy) nanotubes followed by a chemical activation process. NPCN counter electrodes are subsequently fabricated by depositing NPCNs onto Ti mesh for quantum dot-sensitized solar cells (QDSCs). Electrochemical tests are carried out to evaluate the electrocatalytic performance of obtained NPCN electrode. The data of electrochemical tests suggest that the NPCN electrode has a superior electrocatalytic ability towards polysulfide (S₂²⁻/S²⁻) electrolyte regeneration reaction and displays a high stability in polysulfide electrolyte. The excellent electrocatalytic performance of NPCN electrode can be ascribed to their large surface area, 2D porous nanoribbon morphology, and nitrogen atom doping, which provides abundant electrocatalytic active sites and facilitates the electrolyte diffusion. Consequently, a power conversion efficiency of 3.27% is obtained by using NPCN electrode as the counter electrode for QDSC. This efficiency is close to the QDSC assembled with commonly used PbS electrode (4.0%).     

Model interpretation of electrochemical behavior of Pt/H2SO4 interface over both the hydrogen oxidation and oxide formation regions

Hydrogen oxidation (HOR) and oxygen reduction (ORR) reactions are important reactions in the polymer electrolyte membrane fuel cell (PEMFC). However, there are other reactions relating to the kinetics of HOR and ORR, i.e. hydrogen adsorption and oxide formation reactions. Development of the PEMFC catalyst (mostly use Pt) requires kinetic understanding of these reactions taking place at electrodes. In present study, the HOR, ORR, hydrogen adsorption, and oxide formation taking place at Pt/H₂SO₄ interface were kinetically investigated in the whole potential range. Mechanistic study was performed by establishing kinetic equations from the proposed mechanism, derived to the Faradaic current density and impedance in order to fit to the experimental results. Fitting results indicated that the HOR has more kinetic activity on the Pt(110) than Pt(100) sites with the rate constants of 1.60 and 1.20 s⁻¹, respectively. For the Pt oxidation/reduction process, fitting results showed the fast reaction rate of ORR compared with the Pt oxidation. Additionally from the impedance fitting, the electrical parameters (solution resistance, capacitance, Warburg coefficient, constant phase element parameter) of the electrode reactions were determined to complete the interpretation of the reaction mechanisms. This study demonstrated the acquisition of the mathematical model to predict the kinetic information of an electrochemical reaction. The model can be used to predict the electrochemical behavior of any electrochemical reactions, which is benefit for the design of an electrocatalyst.     

Highly durable,Pt free and large-area Ni–B film synthesized by SILAR as a bifunctional electrode for electrochemical water splitting

A search for efficient, durable, large-area, and economic catalyst material for low-cost production of hydrogen and oxygen is currently a high priority in the field of electrocatalysis (EC). In view of this, a cost-effective, earth abundant, highly stable, Pt free, and large-area (8 cm × 8 cm) bifunctional Ni–B electrocatalyst is reported via simple and economic SILAR method. A highly porous surface of Ni–B film with high surface wettability indicated better electrochemical water-splitting properties for the films and is obtained at 100 cycles. A Low over-potential value to obtain HER (49 mV) and OER (340 mV) at 10 mA/cm² current suggested that they are comparable to the well-known Pt and RuO electrodes in alkaline medium (1M KOH), respectively. In actual water-splitting setup having Ni–B film (as cathode) and stainless steel (as anode), the hydrogen production of 612 ml/h is obtained at constant potential, which was enhanced by 18% i.e., 726 ml/h when a Ni–B film as both cathode and anode electrode was used. Both the electrodes are highly stable for over 15 days and interestingly they showed 7% increment in the EC performance.     

钛基Ce掺杂SnO_2-RuO_2电极的制备及其对焦化废水的电解处理

采用溶胶-凝胶法制备了经稀土元素Ce掺杂改性的Ti/RuO_2-SnO_2-Ce电极,利用SEM、XRD、EDS等分析方法对电极表面的形貌、物相和涂层成分进行了表征,利用CV曲线、LSV曲线等检测手段对电极的电化学性能进行了测试。以Ti/RuO_2-SnO_2-Ce电极为阳极,钛板为阴极,构建电化学氧化反应装置,并采用其对焦化废水进行电解处理。结果表明,Ti/RuO_2-SnO_2电极经稀土Ce改性后极板表面活性位点数量明显增大,金属涂层的结晶化程度明显增强,电极的催化氧化活性显著提高。室温条件下,保持pH值为7.83,在电流密度为30mA/cm~2,电解时间为30min时,焦化废水经电解处理后COD去除率可达91.63%,TOC去除率可达66.22%,UV254值下降到0.921。     

Improvement of anode lifetime by flushing during electrofiltration

The paper is focused on the influence of anode flushing on physicochemical conditions in the anode compartment and anode stability during the electrodewatering in electrofilter press. Kaolin suspensions were dewatered in laboratory filter press with stainless-steel electrodes at electric current density of 80 A/m² and pressure of 2?bar. Two electrodewatering methods were compared: conventional (with filtrate drainage) and innovative (with continuous anode flushing using electrolyte solution). Flushing with neutral electrolyte solution significantly reduced the electrochemical anode corrosion, and can be suggested for the improvement of anode lifetime through a better control of physicochemical conditions during electrodewatering.     

W/BDD薄膜电极制备及其电化学性能研究

利用化学气相沉积（CVD）法研制了一种钨基硼掺杂金刚石（W/BDD）薄膜电极，通过扫描电镜和Raman光谱考察了W/BDD薄膜电极的性能，通过电化学方法测定了其在LiCl-KCl熔盐中的电化学窗口和电化学性能。结果表明，研制的W/BDD薄膜电极的BDD薄膜有较好的微观结构；W/BDD薄膜电极在LiCl-KCl熔盐中的电化学窗口约为3.5 V(-2.5～1.0 V，相对于Ag/AgCl参比极电位)；电解过程中，氧离子不与W/BDD薄膜电极表面BDD薄膜层的碳反应，直接被氧化为氧原子；长时间电解不会改变电极表面薄膜层的形貌和结构。