Metal phthalocyanine-linked conjugated microporous polymer hybridized with carbon nanotubes as a high-performance flexible electrode for supercapacitors

Metal phthalocyanine-linked conjugated microporous polymers (MPc-CMPs) have huge potential applications in energy conversion and storage systems. However, the inherent low conductivity limits their practical application. Herein, the MPc-CMPs are hybridized with highly conductive carbon nanotubes (CNTs) via the easy vacuum filtration method. Interestingly, the composite (denoted as CoPc-CMP/CNTs) shows the flexible feature, which can be served as the flexible binder-free electrode for supercapacitors (SCs). As expected, the flexible CoPc-CMP/CNTs exhibits a high specific capacitance of 289.1 F g⁻¹ at a current density of 1 A g⁻¹ and good capacity retention of 82.4% over 1350 cycles at a high current density of 10 A g⁻¹. Furthermore, First-principle calculations are used to elucidate the superiority of CoPc-CMP to other analogues. The good electrochemical performance could be attributed to the synergistic effect from the high pseudocapacitance and good conductivity of CoPc-CMP as well as the capacitive contribution and good conductivity of CNTs. Our strategy provides a new avenue to develop the high-performance SCs via rational integration of MPc-CMPs with highly conductive CNTs.     

A direct formate microfluidic fuel cell with cotton thread-based electrodes

A direct formate microfluidic fuel cell with cotton thread-based electrodes is proposed. The palladium catalyst is directly coated on cotton threads by repeated dipping method to prepare electrodes, which integrates the flow channel and electrode together and provides exposed active sites for enhancing the mass transfer on the anode and cathode. The aqueous anolyte and catholyte transport through cotton threads by capillary force with aid of gravity, eliminating the use of any external pump and facilitating the integration and miniaturization of the whole system. In the experiment, a three-flow channel structure is employed. The fuel is sodium formate and the oxidant is hydrogen peroxide. 1 M Na₂SO₄ solution is introduced into the middle channel formed by cotton threads with no catalyst to alleviate the reactant crossover. Performance is evaluated under various catalyst loadings, fuel concentrations and differences in height between the inlet and outlet. Results show that the fuel cell produces an open circuit voltage (OCV) of 1.41 V. The maximum current density of 74.56 mA cm⁻² and the peak power density of 24.75 mW cm⁻² are yielded when the palladium loading is 1 mg cm⁻¹ and the difference in height between the inlet and outlet is 7 cm, using 4 M HCOONa as fuel. Furthermore, the performance of the fuel cell increases first and then decreases with increasing the palladium loading. The same variation is observed with increasing the fuel concentration. However, the performance gradually increases with increasing the difference in height from 3 cm to 7 cm. The proposed microfluidic fuel cell with cotton thread-based electrodes shows enormous potential as a micro power source for portable devices.     

A simple Ce-doping strategy to enhance stability of hybrid symmetrical electrode for solid oxide fuel cells

Symmetrical solid oxide fuel cell (SSOFC) is a simple and very promising cell for the rest of the most important commercialization process, which has been longing for stable and efficient symmetrical electrodes, from single-phase perovskites to reducible perovskites with in-situ exsolved metal nanoparticles. Herein, we present a new-type hybrid symmetrical electrode consisting of two different perovskite phases for SSOFC, which interact by dynamic compositional change and accordingly improve the electrochemical activity. Furthermore, a simple Ce-doping strategy is successfully developed to solve the redox stability issue of the hybrid symmetrical electrode for SSOFC. Typical Gd_0.65Sr_0.35Co_0.25Fe_0.75O_3-δ (GSCF) consisting of a cubic perovskite phase and an orthorhombic perovskite phase is chosen as a proof-of-concept. Gd_0.65Sr_0.35(Co_0.25Fe_0.75)_0.9Ce_0.1O_3-δ (Ce-GSCF) with an optimized Ce content of only 10% exhibit the enhanced chemical and thermal stability, consisting of a cubic perovskite phase, an orthorhombic perovskite phase and an in-situ exsolved cubic fluorite phase (GDC). More importantly, Ce-GSCF exhibits very high stability in H₂ at 700 °C and a dramatical reduction of averaged thermal expansion coefficient from 19.5 × 10⁻⁶ K⁻¹ to 16.4 × 10⁻⁶ K⁻¹. The single-cell with Ce-GSCF hybrid symmetrical electrode reaches a high maximum power density of 224 mW/cm² at 700 °C, and can work stably for 180 h without any degradation, indicating that the simple Ce-doping strategy is promising to improve stability of hybrid symmetrical electrode for SOFCs.     

燃料电池空气电极的孔道结构调控

燃料电池是将化学能转化成电能的装置，其空气电极催化层的设计，既要包含丰富的、易于接近的反应活性位，也要具备高度连通的电子、质子以及反应物、产物传质通道，因此电极必须具有特定三维几何结构形貌和有序分布的各功能化孔道，确保催化活性位得以充分利用以及反应可以连续进行。针对催化剂孔道的几何结构调控，本文调研了最近报道的一系列研究工作，从模板法、高温相变法、模板/相变复合方法以及基于金属有机框架材料进行孔道设计等四种主要方法出发，综述了该领域的最新研究进展。     

Improvement of fuel cell performances through the enhanced dispersion of the PTFE binder in electrodes for use in high temperature polymer electrolyte membrane fuel cells

In high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs), it is important that the structure of the electrode catalyst layer is formed uniformly. To achieve this, the binder must be well dispersed; however, polytetrafluoroethylene (PTFE), which is commonly employed in the preparation of HT-PEMFCs, is difficult to disperse during electrode manufacture due to its high hydrophobicity. In this study, we fabricate electrodes containing a surfactant to improve the dispersion of the PTFE binder and to enhance reproducibility during electrode manufacture. The electrodes are commonly prepared via a bar coating method, which is known to exhibit poor dispersion due to the small amounts of solvent employed compared to the spraying method. We then compare the properties of the obtained electrodes prepared in the presence and absence of the surfactant through physical and electrochemical characterization. It is found that the electrode containing the surfactant is structurally superior, and its single cell performance is significantly higher (i.e., 0.65 V at 0.2 Am cm⁻²). The single cells are suitable for operation at 150 °C using H₂/air at atmospheric pressure and a total platinum loading of 2.0 mg cm⁻².     

Synthetic curli enables efficient microbial electrocatalysis with stainless-steel electrode

Microbial electrocatalysis systems (MES) provide a cutting-edge solution to global problems associated with the environment and energy, but practical applications are hindered by the expensive electrode materials. Although stainless steel (SS) has been proposed as a promising inexpensive candidate, poor cell/SS interaction results in a low performance for MES. Here, a new synthetic biology approach was established for reinforcing the cell/SS interaction. Hybridized curli nanofibers fused with a metal-binding domain were heterogeneously expressed onto the cell surface, which realized efficient cell binding with the SS electrode. Consequently, it enabled a ~420-fold improvement of the anodic power output and a substantial enhancement of the cathodic Coulombic efficiency (from 0.6 to 4% to over 80%) with an SS electrode. This work demonstrates low-cost MES with an SS electrode and introduces a new avenue to engineer the cell/electrode interaction, which is promising for future practical applications of MES.     

Hydrocarbon-based electrode ionomer for proton exchange membrane fuel cells

The electrode ionomer is a key factor that significantly affects the catalyst layer morphology and fuel cell performance. Herein, sulfonated poly(arylene ether sulfone)-based electrode ionomers with polymers of various molecular weights and alcohol/water mixtures were prepared, and those comprising the alcohol/water mixture showed a higher performance than the ones prepared using higher boiling solvents, such as dimethylacetamide; this is owing to the formation of the uniformly dispersed ionomer catalyst layer. The relation between ionomer molecular weight for the same polymer structure and the sulfonation degree was investigated. Because the chain length of polymer varies with molecular weight and chain entanglement degree, its molecular weight affects the electrode morphology. As the ionomer covered the catalyst, the agglomerates formed were of different morphologies according to their molecular weight, which could be deduced indirectly through dynamic light scattering and scanning electron microscopy. Additionally, the fuel cell performance was confirmed in the current-voltage curve.     

Chlorine-free emission disposal of spent acid etchant in a three-compartment ceramic membrane reactor

Electrochemical technologies for the on-site treatment of spent acid etchant have received great attention due their ease of operation and economic benefits. On the other hand, a large amount of Cl₂ is generated during the electrolysis process, which leads to potential environmental risks. In the present work, a novel threecompartment ceramic membrane flow reactor, including a cathode chamber, an anode chamber, and a gas absorption chamber was developed. The three chambers were divided by an Al₂O₃ ceramic membrane and a breathable hydrophobic anode diffusion electrode (ADE). The Cl₂ evolution onset potential of the ADE was increased to 1.19 V from 1.05 V of the graphite felt, effectively inhibiting the chlorine evolution reaction (CER). The anode-generated Cl₂ diffused into the gas absorption chamber through the ADE and was eventually consumed by the H₂O₂ adsorbent. Cu could be recovered without emitting chlorine due to the special structure of reactor. The current efficiency of copper precipitation and cathode reduction from Cu²⁺ to Cu⁺ reached 97.7% at a working current of 150 mA. These results indicated that the novel membrane reactor had high potential for application in the copper recovery industry.     

Q235碳钢在静止和流动条件下的腐蚀不均匀性研究

目的研究Q235碳钢在静止和流动条件下腐蚀程度和主要腐蚀区域的差异。方法使用丝束电极(WBE)技术和电化学阻抗谱(EIS)技术分别研究了WBE在静止和流动条件下的电流密度分布、电荷转移电阻以及腐蚀形貌的变化和差异,同时分析了电极的极性转换现象。结果流动条件下Q235碳钢的电荷转移电阻明显降低。在静止条件下,Q235碳钢表面阳极电流区域所占的最大比例为47%,且阳极电流峰集中出现在WBE的中间区域,而四周边缘处的阳极电流峰较少。在流动条件下,Q235碳钢表面的阳极电流区域所占的最大比例为58%,阳极电流峰随机分布在整个WBE表面,且电流分布区间明显变窄。浸泡在静止条件下的58~#电极和流动条件下的39~#电极发生了多次极性转换现象。结论 Q235碳钢在静止和流动条件下均发生了明显的不均匀腐蚀现象。流动条件加剧了Q235碳钢的腐蚀且降低了腐蚀不均匀性。静止条件下Q235碳钢的腐蚀区域集中在中间区域,流动条件下Q235碳钢的腐蚀区域随机分布在整个碳钢表面。静止和流动条件下的钢电极均发生了电流的极性转换现象。     

管电极电解铣削深窄槽流场研究

针对封闭深窄盲槽结构的加工难点,提出了一种管电极电解铣削加工工艺。通过仿真软件对电解铣削过程中的流场进行建模仿真,利用高速摄影仪观测流场分析该方法的可行性。采用外径0.8 mm的管电极在不锈钢上进行电解铣削加工深窄槽试验,研究电解液压强对深窄槽轮廓精度的影响规律,成功加工出槽宽(1±0.05)mm、槽深(2.5±0.05)mm的高精度、侧壁陡直的封闭深窄盲槽。