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Proton-exchange membrane fuel cells (PEMFCs) have been widely used commercially to solve the energy crisis and environmental pollution. The oxygen reduction reaction (ORR) at the cathode is the rate-determining step in PEMFCs. Platinum (Pt) catalysts are used to accelerate the ORR kinetics. Pt’s scarcity, high cost, and instability in an acidic environment at high potentials seriously hinder the commercialization of PEMFCs. Therefore, studies should explore electrocatalysts with high catalytic activity, enhanced stability, and low-Pt loading. This review briefly introduces the research progress on Pt and Pt-based ORR electrocatalysts for PEMFCs, including anticorrosion catalyst supports, Pt, and Pt-based alloy electrocatalysts. Advanced preparation technology and material characterization of Pt-based ORR electrocatalysts are necessary to improve the performance and corresponding reaction mechanisms.

Boron-doped amorphous carbon (BDAC) thin films with a regular oxygen reduction reaction (ORR) catalytic activity were synthesized in a hot filament chemical vapor deposition device using a mixture of CH4 and H2 as a gas source and B2O3 as a boron source and then oxidized in air at 380–470 °C for 15–75 min. Scanning electron microscope, transmission electron microscope, Raman spectroscopy, X-ray photoelectron spectroscopy, and electrochemical tests were used to characterize the physical and electrochemical properties of the BDAC catalysts. It was concluded that the BDAC catalyst oxidized at 450 °C for 45 min showed the best ORR catalytic activity in alkaline medium. The oxygen reduction potential and the transfer electron number n, respectively, are − 0.286 V versus Ag/AgCl and 3.24 from the rotating disk electrode experiments. The treated carbon film has better methanol resistance and stability than the commercial Pt/C catalyst.

Background The effects of epicardial connections (ECs) involving pulmonary veins (PVs) in atrial fibrillation (AF) ablation have been revealed recently. However, no systematic approaches to identify and ablate the ECs were established. Methods Patients with AF undergoing radiofrequency (RF) catheter ablation were retrospectively analyzed. ECs were identified when (1) PV isolation (PVI) cannot be achieved after first-pass isolation; (2) PVI was still absent although the conduction gap was detected and ablated; (3) the earliest activation area (EAA) was revealed located within the PV antrum distant from the initial ablation line using high-density mapping (HDM) technique; (4) focal ablation at the EAA was effective to achieve PVI. Relevant pacing maneuvers were performed to elucidate ECs' bidirectional conduction. Results Overall, 36 ECs were identified and ablated in 35/597 (5.86%) patients. Among the 35 patients with ECs, at least one PV insertion of ECs was located at the carina region. The most common pattern was a single breakthrough in 31 (88.6%) patients, followed by multiple breakthroughs in 3 and wide breakthroughs in 1. The median distance from EAA to the initial ablation line was 10.0 mm. The average number of RF energy delivery was 1.75 ± 1.00, and single RF delivery was adequate in 16/36 (44.4%) patients. Continuous potentials were present at the EAA in 9/34 (26.5%) patients. Conclusion ECs were confirmed and ablated successfully in 5.86% (35/597) AF patients using HDM. PV insertions of ECs were mainly located at the carina region. Continuous potentials might assist in the prediction of ECs.

Based on $$d$$ -dimensional Bell states, a new semi-quantum private comparison protocol is designed under the assistance of a semi-honest third party. Compared with the existing semi-quantum private comparison protocols, the presented semi-quantum private comparison protocol could compare the size relation between two classical participants’ secrets in one-time execution without divulging their secrets. This could reduce the consumption of quantum resources and raise the efficiency of the proposed semi-quantum private comparison protocol. The correctness of the suggested protocol is validated and further supported by giving some examples. The performance of this protocol against external attacks and internal attacks has also been analyzed.

Pulmonary vein isolation (PVI) is the cornerstone therapy of atrial fibrillation (AF). Radiofrequency catheter ablation (RFCA) is performed using a point-by-point method to achieve durable PVI. However, this procedure remains complex and time-consuming, and the long-term clinical outcomes are still not satisfactory. Recently, there has been increasing interest in the clinical application of high-power short-duration (HPSD) approaches in the field of RFCA. HPSD ablation, distinguishing it from the conventional ablation strategy, delivers RF energy at a high power and saves the dwell time at each site. It is unknown whether the HPSD approach can bring some gratifying changes in the field of RF energy ablation. A number of experimental studies and clinical studies have been conducted regarding this topic. The review aimed to summarize the research findings and evaluate the procedural efficiency, safety, and clinical outcomes of the HPSD approach based on the evidence available to date.

Carbon films have been prepared by the hot filament chemical vapor deposition method at different methane concentrations. The morphology, microstructure, and chemical bonding states of the deposited films were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The electrocatalytic oxygen reduction reaction (ORR) activity of these carbon catalysts in alkaline solution was investigated using rotating disk electrode (RDE) voltammetry. The experimental results show that the sp2/sp3 value increases with increasing methane concentration (MC), while the ID/IG value (integral area ratio of D and G band) gradually becomes larger and reaches the maximum at a MC of 3%, then decreases. With an increase in the MC, the ORR peak potential successively shifts to a more positive value and remains a constant at the MC of 3.5%. The peak current density consecutively increases to a summit at the MC of 3% and then begins to decrease. The onset potential shifts positively and the limiting diffusion current density at −1.0 V increases gradually, indicating that the catalytic activity towards ORR of the catalysts is progressively enhanced. When the MC is more than 3%, the catalytic activity begins to decay. Moreover, the catalysts with a better ORR activity have a poorer durability and methanol tolerance.

Porous boron doped diamonds (BDDs) were obtained on foam nickel substrates with a porosity of 80%, 85%, 90% and 95% respectively by hot filament chemical vapor deposition (HFCVD) technology. Scanning electron microscopy (SEM) reveals that uniform and compact BDDs with a cauliflower-like morphology have covered the overall frame of the foam nickel substrates. Raman spectroscopy shows that the BDDs have a poor crystallinity due to heavily doping boron. X-ray photoelectron spectroscopy (XPS) analysis effectively demonstrates that boron atoms can be successfully incorporated into the crystal lattice of diamonds. Electrochemical measurements indicate that the oxygen reduction potential is unaffected by the specific surface area (SSA), and both the onset potential and the limiting diffusion current density are enhanced with increasing SSA. It is also found that the durability and methanol tolerance of the boron doped diamond catalysts are attenuated as the increasing of SSA. The SSA of the catalyst is directly proportional to the oxygen reduction activity and inversely to the durability and methanol resistance. These results provide a reference to the application of porous boron doped diamonds as potential cathodic catalysts for the oxygen reduction reaction in alkaline solution by adjusting the SSA.

Introduction Radiofrequency catheter ablation is an effective therapy for focal idiopathic outflow tract ventricular arrhythmia (OTVA). However, visual inspection of the unipolar electrogram (EGM) QS morphology is subjective with a poor specificity for predicting successful ablation sites. This study aims to evaluate the predictive value of unipolar and bipolar EGMs in OTVA mapping and ablation. Methods and results Twenty-two patients scheduled for idiopathic OTVA ablation were prospectively enrolled. During the procedure, unipolar and bipolar EGMs were recorded simultaneously and visually inspected by the operator to identify their values for predicting arrhythmogenic sites. Quantitative features of the unipolar EGM including the ratio of amplitude of the first positive peak versus the nadir (R-ratio), the maximum descending slope (MaxSlope), and the time interval between the initial deflection point to the MaxSlope (D-Max) were calculated for each target site in offline analysis. EGMs from 100 sites were collected in 20 patients and analyzed. The bipolar reverse polarity characteristic was not as practical for identifying successful ablation site as the unipolar QS characteristic. Successful ablation sites demonstrated smaller R-ratio and shorter D-Max than unsuccessful sites, but no significant difference in MaxSlope. A unipolar EGM-derived quantitative criterion provided significantly better specificity (0.70) than visual inspection (0.37) without compromising on the sensitivity (0.83 vs. 0.89). Conclusion The bipolar reverse polarity characteristic was not a practical method for identifying target in idiopathic OTVA ablation. The unipolar EGM-derived quantitative criteria have better predictive performance than visual inspection of the QS characteristic and are likely to reduce unnecessary ablation sites.

This paper proposes a new type of fabricated shear wall system, that is, the two ends of the horizontally distributed ribs and the top of the vertical distributed ribs are reliably connected with the cast-in-situ belt, and the bottom of the vertical distributed ribs is not penetrated and only connected by mortar. To study the seismic performance of the new wall, 7 specimens of the shear wall were designed and manufactured, including 2 cast-in-place shear walls and 5 new fabricated shear walls. Through low-cycle reciprocating loading tests, different analyses were made. Shear span ratio and different edge restraint structure of the new fabricated shear wall failure mode, bearing capacity and other seismic performance, and through OpenSees finite element analysis of the wall to verify the correctness of the modelling method. The test results show that the failure characteristics of the new wall are mainly the cracking and penetration of the mortar layer, the crushing of the corner concrete and the local buckling of the steel bars at the bottom of the edge members; compared with the cast-in-place wall, the new wall has the lower bearing capacity, but the deformation and energy consumption are not much different. The reinforced edge members can effectively compensate for the weakening of the integrity of the wall panel caused by the discontinuity of vertical steel bars. Among the 7 specimens, the overall performance of the wall with increased longitudinal reinforcement ratio is the best. The error between the wall finite element results and the test results is less than 5%, which shows that the modelling method in this paper has sufficient accuracy for the evaluation of the seismic performance of the new wall. In general, the new prefabricated shear wall system is feasible in high-rise buildings.

选取W-AlN金属-介质型选择性吸收涂层为研究对象, 用金属W作为红外反射层, W-AlN作为吸收层, AlN作为减反层, 利用Mathematica软件对该涂层的金属W体积分数和吸收层、减反层的厚度等参数进行优化计算, 优化结果表明: 吸收层中金属W的体积分数对涂层的选择吸收性能有直接影响; 与高金属吸收层相比, 低金属吸收层的厚度对涂层选择吸收性能的影响较显著; 低/高金属吸收层中金属W体积分数的最优值分别为0.2/0.8, 而最优厚度分别为0.1/0.05 m m, 此时涂层的吸收率为0.841, 发射率为0.021; 加入厚度为0.06 m m的AlN减反层后, 吸收率达到0.920, 发射率为0.022; 加入厚度适当的减反层可以有效提高涂层的吸收率, 同时也会使发射率随之增加; 增加减反层和低金属吸收层厚度都会使涂层的反射率骤升阈值波长发生红移. 利用磁控溅射方法在抛光的不锈钢表面制备了W/W-AlN/AlN选择吸收涂层, 各层膜厚度和吸收层中金属体积分数都严格遵循优化结果, 测试所得涂层的反射率曲线、吸收率和发射率均与优化结果符合良好.

Bipolar plates are one of the most important components in PEMFC stack and have multiple functions, such as separators and current collectors, distributing reactions uniformly, and etc. Stainless steel is ideal candidate for bipolar plates owing to good thermal and electrical conductivity, good mechanical properties etc. However, stainless steel plate still cannot resist the corrosion of working condition. In this work, ternary Ti–Mo–N film was fabricated on 316L stainless steel (SS316L) as a surface modification layer to enhance the corrosion resistance. Effects of Mo content on the microstructure and corrosion resistance of Ti–Mo–N films are systematically investigated by altering sputtering current of the Mo target. XRD results reveal that the preferred orientation changes from [111] to [220] direction as Mo content in the film increases. The synthesized Ti–Mo–N films form a substitutional solid solution of (Ti, Mo)N where larger Mo atoms replace Ti in TiN crystal lattice. The TiN-coated SS316L sample shows the best corrosion resistance. While Mo content in the Ti–Mo–N films increases, the corrosion resistance gradually degrades. Compared with the uncoated samples, all the Ti–Mo–N film coated samples show enhanced corrosion resistance in simulated PEMFC working condition.

Graphite powders with particle sizes of 40, 100, 400, and 1000 nm were used as cathode catalysts. The influence of graphite particle size on the electrocatalytic behavior towards the oxygen reduction reaction (ORR) was investigated. The catalytic activity and kinetics of the ORR, and methanol tolerance were tested in alkaline solutions with saturated oxygen via cyclic voltammetry (CV), rotating disk electrode (RDE) and amperometric i-t curve techniques. Experimental results show that the ORR process of the graphite catalyst with a particle size of 40 nm was close to the four-electron pathway at -0.6 V, exhibiting the best ORR activity. This is ascribed to a greater number of edge defects as ORR active sites in the carbonmaterial. The number of sites can be characterized with X-ray diffraction (XRD) and Raman spectroscopy. Additionally, these graphite catalysts have been demonstrated a superior tolerance to methanol than the commercial 20 wt.% Pt/C electrode in alkaline solutions.

The purpose of this study was to investigate the most common site for conduction gaps post first ablation of typical atrial flutter(AFL) with high density mapping(HDM) of right atrium, trans-isthmus conduction(TIC) time after re-abltiaon and the long-term outcomes of HDM-guided ablation. Eighty