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Combining the abundance and inexpensiveness of their constituent elements with their atomic dispersion, atomically dispersed Fe-N-C catalysts represent the most promising alternative to precious-metal-based materials in proton exchange membrane (PEM) fuel cells. Due to the high temperatures involved in their synthesis and the sensitivity of Fe ions toward carbothermal reduction, current synthetic methods are intrinsically limited in type and amount of the desired, catalytically active Fe-N4 sites, and high active site densities have been out of reach (dilemma of Fe-N-C catalysts). We herein identify a paradigm change in the synthesis of Fe-N-C catalysts arising from the developments of other M-N-C single-atom catalysts. Supported by DFT calculations we propose fundamental principles for the synthesis of M-N-C materials. We further exploit the proposed principles in a novel synthetic strategy to surpass the dilemma of Fe-N-C catalysts. The selective formation of tetrapyrrolic Zn-N4 sites in a tailor-made Zn-N-C material is utilized as an active-site imprint for the preparation of a corresponding Fe-N-C catalyst. By successive low- and high-temperature ion exchange reactions, we obtain a phase-pure Fe-N-C catalyst, with a high loading of atomically dispersed Fe (>3 wt %). Moreover, the catalyst is entirely composed of tetrapyrrolic Fe-N4 sites. The density of tetrapyrrolic Fe-N4 sites is more than six times as high as for previously reported tetrapyrrolic single-site Fe-N-C fuel cell catalysts.

Peng Zhang, Xiu-Wu Han, Xin Zhang, Xu-Hui Zhu, Tao Li, Yan-Sheng Li, Yuan-Hao Chen, Gao Li Department of Urology, Beijing Chao-Yang Hospital, Beijing, People’s Republic of ChinaCorrespondence: Xiu-Wu HanDepartment of Urology, Beijing Chao-Yang Hospital, Capital Medical University, 5 Jingyuan Road, Shijingshan District, Beijing, People’s Republic of ChinaTel +86 10-13501356960Email hanxiuwu47859@163.comObjective: The present study aimed to observe and discuss the effectiveness and safety of the UreTron single-probe ultrasonic intracorporeal lithotripter in ureteroscopic lithotripsy.Methods: The clinical data of patients with unilateral solitary ureteral calculi treated with ureteroscopic lithotripsy who were hospitalized at the Department of Urology (West District) of Beijing Chaoyang Hospital between March 2016 and August 2020 were selected for retrospective analysis. The patients were divided into the UreTron group (group U) and holmium laser group (group H) according to the lithotripsy method adopted. The operation duration, length of hospital stay, stone clearance rate, proportion of patients requiring flexible ureteroscopy-assisted lithotripsy, and complications were compared between the groups.Results: There was no statistical difference between the groups in terms of the general characteristics, operation duration, or length of hospital stay (P > 0.05). Regarding the stone clearance rate (group U=93.5%; group H=75%), proportion of patients requiring flexible ureteroscopy-assisted lithotripsy (group U=6.5%; group H=27.8%), and incidence of surgical complications (group U=1 case; group H=9 cases), group U was superior to group H, and the differences between the groups were statistically significant (P < 0.05). However, the differences in other complications (cardiocerebral complications and lower extremity thrombosis) were not statistically significant between the groups (P > 0.05).Conclusion: The UreTron system is a new lithotripsy apparatus that is safe and effective for ureteroscopic lithotripsy and has certain advantages in terms of the stone clearance rate, proportion of patients requiring flexible ureteroscopy-assisted lithotripsy, and surgical complications, making it worthy of clinical application.Keywords: UreTron, holmium laser, ureteral calculi, lithotripsy

Introduction Laparoscopic renal cyst decortication is currently the best choice for the treatment of simple renal cysts and is widely used in clinical practice Aim To investigate the safety and clinical efficacy of two-trocar mini-laparoscopic decortication of adult renal cysts. Material and methods A total of 90 patients were enrolled in the study and randomly divided into two groups: a two-trocar mini-laparoscopic treatment group (M group) and a three-trocar standard laparoscopic treatment group (S group), with 45 patients in each group. Results The average length of hospital stay was shorter, and the demand for postoperative analgesics was less in the M group than in the S group (p < 0.05). The proportion of “very satisfied” patients in the patient physical recovery satisfaction survey was significantly higher in the M group than in the S group (p < 0.05). Of the 45 patients in the M group, 40 successfully underwent surgery. In 3 patients, the two-trocar procedure was converted to a three-trocar procedure due to difficulty in separating perirenal adhesion for visualization. Mini-laparoscopic surgery was converted to classic laparoscopic surgery in 2 patients. In the S group, 44 patients successfully underwent the renal cyst decortication procedure. One patient underwent partial renal resection due to an intraoperative diagnosis of multilocular cystic renal cell carcinoma. Postoperative urine leakage was reported in 3 patients in the M group and two in the S group. Conclusions Two-trocar mini-laparoscopic treatment of renal cysts is as safe and effective as traditional laparoscopy but is associated with less cosmetic damage, leading to a better physical appearance.

Microtopography of fiber of Discorea nipponica Makino before and after mechanical activated by AGO-2 planetary mill was observed by SEM, and they changed the thick floccules to fine particles (D50 particle sizes were 10.18μm). Discorea fiber powder after mechanical activation had a narrow size distribution. According to XRD, the granularity and structures of discorea fiber with and without mechanical activation significantly differed, and the crystalline of discorea fiber was significantly converted into amorphous state after mechanical activation. On the basis of TG–DSC analysis, the activity of discorea fiber was enhanced, and certain internal energy were stored, and complete decomposition in advance. According to FT-IR, none of the functional groups of the mechanically activated discorea fiber disappeared, and no new functional groups appeared, which indicate that mechanical activation does not induce a chemical transformation of discorea fiber. According to the activation energy analysis, the thermal activation energy of dioscorea fiber after mechanical activation was18.49 kJ•mol, and the mechanical transfer activation energy was 56.06 kJ•mol, indicating that about 1/3 of the mechanical transfer activation energy was stored in the activated dioscorea fiber fine powder in the form of surface energy and internal energy.

The use of purge flow in gas turbines allows for high turbine entry temperatures, which are essential to produce high cycle efficiency. Purge air is bled from the compressor and reintroduced in the turbine to cool vulnerable components. Wheel-spaces are formed between adjacent rotating and stationary discs, with purge air supplied at low radius before exiting into the mainstream gas-path through a rim-seal at the disc periphery. An aerodynamic penalty is incurred as the purge flow egress interacts with the mainstream. This study presents unparalleled three-dimensional velocity data from a single-stage turbine test rig, specifically designed to investigate egress-mainstream interaction using optical measurement techniques. Volumetric Velocimetry is applied to the rotating environment with phase-locked measurements used to identify and track the vortical secondary flow features through the blade passage. A baseline case without purge flow is compared to experiments with a 1.7% purge mass fraction; the latter was chosen to ensure a fully sealed wheel-space. A non-localised vortex tracking function is applied to the data to identify the position of the core centroids. The strength of the secondary-flow vortices was determined by using a circulation criterion on rotated planes aligned to the vortex filaments. The pressure-side leg of the horseshoe vortex and a second vortex associated with the egress flow were identified by the experimental campaign. In the absence of purge flow the two vortices merged, forming the passage vortex. With the addition of purge flow, the two cores remained independent to 40% of the blade axial chord, while also demonstrating an increased radial migration and intensification of the passage vortex. The egress core was shown to remain closer to the suction-surface with purge flow. Importantly, where the vortex filaments demonstrated strong radial or tangential components of velocity, the circulation level calculated from axial planes underpredicted the true circulation by up to 50%.

The application of proton exchange membrane fuel cells (PEMFCs) in light-duty vehicles (LDV) has dominated the fuel cell research field for the past decades. To reduce the LDV FC system cost to 30 $/kW by 2025 has driven the search for highly active cathode catalysts that could substitute the costly state-of-the-art Pt-alloy catalysts or reduce the cathode loadings to < 0.125 mgPt/cm2.1, 2 As novel ORR catalyst continue to emerge, theoretical calculations have turned the attention on Pt-rare earth (RE) alloys, such as platinum-yttrium alloys that were suggested to have superior activity for the oxygen reduction reaction (ORR) and superior long-term stability compared to conventional carbon-supported platinum catalyst (Pt/C). 3 Based on these findings, many attempts have been made to produce high electrochemical surface area (ECSA) Pt-RE alloy catalysts.4 In recent years, Hu, et al. introduced a new synthesis procedure that utilizes a carboiimide-assisted synthesis for the preparation of Pt-RE/C catalysts with an unprecedentedly high ECSAs in the range of ~50-60 m2/gPt.5 With such high ECSA PtxY/C catalysts, good PEMFC performance would be expected, but to date the ORR activity and stability of such PtxY/C catalysts has not been demonstrated in a PEMFC environment. In view of this, we reproduced the synthesis reported by Hu et al. using a Ketjen Black (KB) carbon support. The resulting PtxY/KB catalyst was characterized by X-ray diffraction, X-ray spectroscopy (EDS) in scanning transmission electron microscopy (STEM), and elemental analysis, indicating the formation of a Pt-richshell/Pt3Ycore structure that was caused by the acid washing procedure introduced before the electrochemical characterization.5 In our present study, two different Pt/KB catalysts were selected as reference materials: i) a Johnson Matthey reference catalyst consisting of small well-dispersed Pt nanoparticles on a KB support (Pt/KB-JM); ii) an in-house synthesized Pt/KB catalyst (Pt/KB-syn.) with a similar particle size distribution and ECSA as the in-house synthesized PtxY/KB catalyst (PtxY/KB-syn.). The ECSA (via CO-stripping voltammetry) and the ORR mass activity at 0.9 V vs. RHE (imass 0.9 V) of these three catalysts were first evaluated by rotating disk electrode (RDE) measurements in 0.1 M HClO4 at 25 °C. The catalysts were also incorporated as cathode catalysts in membrane electrode assemblies (MEAs), first determining their ECSA (by CO-stripping) and then their H2/O2 and H2/air performance in a 5 cm2 single-cell PEMFC hardware at 80 °C under differential flow conditions, including a quantification of the ORR mass activity at 0.9 V vs. RHE at 100 kPa O2. As can be seen in Figure 1, the relative ECSA and ORR mass activity values of the three different catalysts obtained in the RDE and the PEMFC configuration were essentially identical when evaluated at the same ionomer to carbon ratio (I/C = 0.7, g/g). Furthermore, a comparison of the RDE ORR activity at two different I/C ratios showed that the PtxY/KB-syn. and Pt/KB-syn. catalysts were more susceptible to ionomer poisoning when compared to the Pt/KB-JM catalyst. Following the approach taken in our previous publications, the voltage-cycling stability of the synthesized catalysts was also evaluated using an accelerated stress test (AST) consisting of a triangular potential scan between 0.6 and 1.0 VRHE at 50 mV/s up to 30000 cycles.5 Overall, the RDE and PEMFC data showed that the here synthesized carbon-supported Pt-richshell/Pt3Ycore catalyst does not shown an enhanced ORR activity nor a long-term stability benefit when compared to a Pt/KB catalyst with the same ECSA, contrary to what had been hypothesized earlier.3 References R. L. Borup, A. Kusoglu, K. C. Neyerlin, R. Mukundan, R. K. Ahluwalia, D. A. Cullen, K. L. More, A. Z. Weber and D. J. Myers, Current Opinion in Electrochemistry, 21, 192–200 (2020). M. Escudero-Escribano, K. D. Jensen and A. W. Jensen, Current Opinion in Electrochemistry, 8, 135–146 (2018). J. Greeley, I. E. L. Stephens, A. S. Bondarenko, T. P. Johansson, H. A. Hansen, T. F. Jaramillo, J. Rossmeisl, I. Chorkendorff and J. K. Nørskov, Nature Chemistry, 1(7), 552–556 (2009). J. N. Schwämmlein, G. S. Harzer, P. Pfändner, A. Blankenship, H. A. El-Sayed, and H. A. Gasteiger, Journal of the Electrochemical Society(165 (15)), J3173-J3185 (2018). Y. Hu, J. O. Jensen, L. N. Cleemann, B. A. Brandes and Q. Li, Journal of the American Chemical Society, 142, 953–961 (2020). Acknowledgment This work has been supported by the Fuel Cells and Hydrogen 2 Joint Undertaking under grant agreement No. 826097 (GAIA). This Joint Undertaking receives support from the European Union’s Horizon 2020 research and innovation programme, Hydrogen Europe and Hydrogen Europe Research. Figure 1

PM

Typical turbomachinery aerothermal problems of practical interest are characterized by flow structures of wide-ranging scales, which interact with each other. Such multiscale interactions can be observed between the flow structures produced by surface roughness and by the bulk flow patterns. Moreover, additive manufacturing (AM) may sooner or later open a new chapter in the way components are designed by granting designers the ability to control the shape and patterns of surface roughness. As a result, surface finish, which so far has been treated largely as a stochastic trait, can be shifted to a set of design parameters that consist of repetitive, discrete micro-elements on a wall surface (“manufacturable roughness”). Considering this prospective capability, the question would arise regarding how surface microstructures can be incorporated in computational analyses during designing in the future. Semi-empirical methods for predicting aerothermal characteristics and the impact of manufacturable roughness could be used to minimize computational cost. However, the lack of element-to-element resolution may lead to erroneous predictions, as the interactions among the roughness micro-elements have been shown to be significant for adequate performance predictions (Kapsis and He, 2018, “Analysis of Aerothermal Characteristics of Surface Micro-Structures,” ASME J. Fluids Eng., 140(5), p. 051104). In this paper, a new multiscale approach based on the novel block spectral method (BSM) is adopted. This method aims to provide efficient resolution of the detailed local flow variation in space and time of the large-scale microstructures. This resolution is provided without resorting to modeling every single ones in detail, as a conventional large-scale computational fluid dynamics (CFD) simulation would demand, but still demonstrating similar time-accurate and time-averaged flow properties. The main emphasis of this work is to develop a parallelized solver of the method to enable tackling large problems. The work also includes a first of the kind verification and demonstration of the method for wall surfaces with a large number of microstructured elements.

Heteroatom-doped carbons have been substantially applied on electrochemical applications for their exceptional electrocatalytic ability and electric conductivity. Among the doping elements, electron-deficient boron (B) is considered to be a promising heteroatom for the chemical doping of carbon materials to modify the chemically inert sp2 carbon structure and thus activate the abundant free‐flowing π electrons. In this study, B-doped carbon nanotubes (BCNTs) with various boron doping atomic percentages (0.40–3.92 at%) are synthesized and used as a electrocatalyst on the counter electrode (CE) of dye-sensitized solar cells (DSSCs) for investigating the effect of boron doping on carbon materials. A solar-to-electricity conversion efficiency (η) of 7.17 ± 0.11% is achieved for a DSSC with a CE containing BCNTs with optimized B doping concentration (BCNT-0.40 at%), which is higher than that of the cells with CEs consisting of pristine carbon nanotubes (CNT, η = 5.98 ± 0.20%) and is comparable to that of the cell with a Pt CE (η = 7.98 ± 0.05%). It is also noteworthy from a practical viewpoint that the developed atmospheric-pressure synthesis method for synthesizing BCNT is amenable to industrial-scale production since a requirement for vacuum system can be avoided.

Platinum-group-metal-free (PGM-free) catalysts are currently considered as potential oxygen-reduction-reaction (ORR) catalysts to replace costly and supply-limited platinum at the cathode side of proton exchange membrane fuel cells (PEMFCs). Extensive research efforts have led to substantial progress with regards to the ORR activity of PGM-free ORR catalysts, but there is uncertainty about the dependence of the mass activity on the catalyst loading. In this study, the effect of catalyst loading on the mass activity is investigated by means of rotating disk electrode measurements as well as single cell PEMFC tests using a commercial PGM-free ORR catalyst. Single cell tests with a wide range of loadings (0.4–4.0 mgcat cm−2 MEA) are compared to rotating disk electrode measurements with low loadings of 40–600 μgcat cm−2 disk. In contrast to indications in the literature that the ORR activity depends on catalyst loading, our results reveal an independence of the ORR mass activity from the catalysts loading in both RDE and PEMFC tests, if corrections for the voltage losses in H2/O2 single cell tests are considered. Moreover, no clear relation of the stability to the catalyst loading was found in H2/O2 PEMFCs.

Objective To evaluate the diagnostic significance of PLA2R and IgG4 in elderly patients with idiopathic membranous nephropathy (IMN). Methods The clinical data were retrospectively analyzed of patients with IMN (49 males and 49 females, aged 66.6±5.4 years) or Non-IMN (57 males and 41 females, aged 67.1±6.5 years) who were admitted in the authors served Department of Nephrology from Apr. 2014 to Feb. 2016 and accepted renal biopsy. SPSS13.0 was employed to evaluate the sensitivity, specificity and calculate the area under ROC curve (AUC) of serum anti-PLA2R antibody, glomerular PLA2R and IgG1-4 subclasses on diagnosing IMN. Results On diagnosing IMN, the sensitivity and specificity of serum anti-PLA2R antibody were 77.6% and 89.8% [AUC=0.869(0.816-0.923)], of glomerular PLA2R were 66.3% and 94.9% [AUC=0.805(0.741- 0.87)], and of glomerular IgG1-IgG4 were 80.6% and 78.6%, 60.2% and 83.7%, 41.8% and 84.7%, and 93.9% and 89.8%, respectively [AUC=0.767(0.696-0.838), 0.709(0.635-0.783), 0.628(0.549-0.706) and 0.94(0.901-0.978), respectively]. As to the combined use of glomerular PLA2R and IgG4 on diagnosing IMN, the sensitivity was 93.9% when either one of glomerular PLA2R and IgG4 was positive, or the specificity was 96.9% when both glomerular PLA2R and IgG4 were positive. Conclusion PLA2R and IgG4 can effectively serve the diagnosis of IMN, and the combined use of PLA2R and IgG4 may be better than single indicator alone. DOI: 10.11855/j.issn.0577-7402.2017.09.11

A systematic study to reveal the relationship between the surface oxygen-containing functionalities of sub-10-nm GNRs and their electrochemical properties for lithium-ion batteries has been presented. Sub-10-nm GNRs with controlled oxygen-containing groups were synthesized by a green and scalable intercalation-assisted unzipping SWCNTs. Detailed materials characterizations including TEM, XRD, Raman and XPS indicate that KNO 3 could be an effective intercalation agent to facilitate the SWCNT unzipping by reducing the strong Van der Waals force attraction of bundled SWCNT. The levels of surface functionalities of sub-10-nm GNR were tuned by carefully controlling the KMnO 4 concentration during the unzipping process. The electrochemical analysis suggests that the as-produced sub-10-nm GNR with 31.4 atomic percent (atom %) oxygen-containing functional groups showed the highest capacity of 490.4 mAh g −1 after 100 cycles. This work proposed that sub-10-nm GNRs with appropriate oxygen-functional groups can be a promising electrode material for high performance lithium-ion batteries.

An atmospheric pressure, solution-assisted substitution process has been developed to produce boron-doped carbon nanotubes (BCNTs) with tunable boron dopant concentrations precisely from atomic percent of 0.4–3.9% by controlling the reaction conditions. The systematic material characterizations and detailed electrochemical sensor applications were studied. The electrochemical detection of dopamine (DA) can be improved by the enhanced electrocatalytic activity and reduced electron transfer resistance of BCNTs due to the boron doping. The effects of boron dopant concentrations on the electrocatalytic activity and electron transfer resistance of the BCNTs were investigated thoroughly in this study. It was found experimentally that the anodic peak current density (ipa) of DA is the highest (169.6 ± 8.9 μA cm−2) on the BCNTs (B 2.1 at.%) modified screen printed carbon electrode (SPCE). In this study, we have successfully developed a highly efficient and tunable synthesis of BCNTs in bulk quantities as the potential electrocatalysts for DA oxidation reaction. Also, it is noteworthy from a practical point of view that the developed atmospheric-pressure BCNTs synthesis method is amenable to industrial-scale production since it avoids the need for a vacuum system.

In this work, we developed a field effect transistor (FET) biosensor utilizing solution-processed graphene oxide nanoribbon (GONR) for methylene blue (MB) sensing. MB is a unique material; one of its crucial applications is as a marker in the detection of biomaterials. Therefore, a highly sensitive biosensor with a low detection limit that can be fabricated simply in a noncomplex detection scheme is desirable. GONR is made by unzipping multiwall carbon nanotubes, which can be mass-produced at low temperature. The GONR-FET biosensor demonstrated a sensitivity of 12.5μA/mM (determined according to the drain current difference caused by the MB concentration change). The Raman spectra indicate that the materials quality of the GONR and the domain size for the C=C sp2 bonding were both improved after MB detection. X-ray photoelectron spectroscopy revealed that the hydroxyl groups on the GONR were removed by the reductive MB. According to XPS and Raman, the positive charge is proposed to transfer from MB to GONR during sensing. This transfer causes charge in-neutrality in the GONR which is compensated by releasing •OH functional groups. With high sensitivity, a low detection limit, and a simple device structure, the GONR-FET sensor is suitable for sensing biomaterials.

Background:Cerebral small vessel disease (SVD) is the common cause of cognitive decline in the old population. MRI can be used to clarify its mechanisms. However, the surrogate markers of MRI for early cognitive impairment in SVD remain uncertain to date. We investigated the cognitive impacts of cerebral microbleeds (CMBs), diffusion tensor imaging (DTI), and brain volumetric measurements in a cohort of post-stroke non-dementia SVD patients.Methods:Fifty five non-dementia SVD patients were consecutively recruited and categorized into two groups as no cognitive impairment (NCI) (n = 23) or vascular mild cognitive impairment (VaMCI) (n = 32). Detailed neuropsychological assessment and multimodal MRI were completed.Results:The two groups differed significantly on Z scores of all cognitive domains (all p < 0.01) except for the language. There were more patients with hypertension (p = 0.038) or depression (p = 0.019) in the VaMCI than those in the NCI group. Multiple regression analysis of cognition showed periventricular mean diffusivity (MD) (β = −0.457, p < 0.01) and deep CMBs numbers (β = −0.352, p < 0.01) as the predictors of attention/executive function, which explained 45.2% of the total variance. Periventricular MD was the independent predictor for either memory (β = −0.314, p < 0.05) or visuo-spatial function (β = −0.375, p < 0.01); however, only small proportion of variance could be accounted for (9.8% and 12.4%, respectively). Language was not found to be correlated with any of the MRI parameters. No correlation was found between brain atrophic indices and any of the cognitive measures.Conclusion:Arteriosclerotic CMBs and periventricular white matter disintegrity seem to be independent MRI surrogated markers in the early stage of cognitive impairment in SVD.

A polymeric dispersant is usually used for preparing the uniform multiwalled carbon nanotubes (CNT) film for replacing Pt as the catalyst on the counter electrode (CE) of dye-sensitized solar cells (DSSCs). However, it is necessary to remove the polymeric dispersant completely due to its nonconductive property. Herein, boron-doped CNT (BCNT) with enhanced thermal stability, as the benefit to the dispersant removal, was prepared as the catalyst on the CE of a DSSC, and the cells with pristine CNT and Pt as the catalyst on the CEs were compared. The BCNT based DSSC shows the best light-to-electricity conversion efficiency (η) of 7.91 ± 0.21%, which is higher than that of the cell with a CNT CE (η = 6.02 ± 0.19%) and is comparable to that of the cell with a Pt CE (η = 8.03 ± 0.11%).

Typical turbomachinery aerothermal problems of practical interest are characterised by flow structures of wide-ranging scales, which interact with each other. Such multi-scale interactions can be observed between the flow structures produced by surface roughness and by the bulk flow patterns. Moreover, additive manufacturing may sooner or later open a new chapter in component designs by granting designers the ability to control the surface roughness patterns. As a result, surface finish, which so far has been treated largely as a stochastic trait, can be shifted to a set of design parameters that consist of repetitive, discrete micro-elements on a wall surface (‘manufacturable roughness’). Considering this prospective capability requirement, the question would arise regarding how surface micro-structures can be incorporated in computational analyses during a design phase in the future. Semi-empirical methods for predicting aerothermal characteristics and the impact of manufacturable roughness could be used to minimise computational cost. However, the lack of element-to-element resolution may lead to erroneous predictions, as the interactions among the roughness micro-elements have been shown to be significant for adequate performance predictions [1]. In this paper a new multi-scale approach based on the novel Block Spectral method is adopted. This method aims to provide efficient resolution of the detailed local flow variation in space and time of the large scale micro-structures. This resolution is provided without resorting to modelling every single ones in detail, as a conventional large scale CFD simulation would demand, but still demonstrating similar time-accurate and time-averaged flow properties. The main emphasis of the present work is to develop a parallelised solver of the method to enable tackling large problems. The work also includes a first of the kind verification and demonstration of the method for wall surfaces with a large number of micro-structured elements.

Recently, the notable efforts placed on investigating platinum group metal (PGM)-free catalysts (M-N-C catalysts, M = Fe, Co, & Mn) for the oxygen reduction reaction (ORR) have led to the possible development of low-cost proton exchange membrane fuel cells (PEMFCs).1 However, compared to PGM ORR catalysts, the lower turnover frequency and active site density of PGM-free catalysts generally require high-surface-area structures and high catalyst loadings to achieve reasonable low-current density performance in PEMFCs, thereby resulting in significant ionic, mass, and electronic transport overpotentials. 2 With regards to these transport resistances, an intriguing observation from the PEMFC performance with PGM-free cathode catalysts is the significantly higher electronic overpotential (iR-drop) when compared to PGM-based cathode catalysts (e.g., Pt/C). This increased iR-drop results in an increase of the high frequency resistance (HFR) due to the high electrical resistivity (ρe- in Ω/cm) of the thick PGM-free cathode catalyst layers. While ρe- of conventional Pt/C electrodes is rather low (~0.5-1 Ω/cm) and results in negligible overpotential losses, ρe- of PGM-free cathode layers can be higher by a factor of ~10-20 due to poor electrical conductivity of the active site (e.g., Fe-N-C) and the high-surface area structures of these catalysts. While several studies have revealed the impact of ionic and mass transport resistances of PGM-free cathode electrodes,3,4 the impact of electrical resistance is still unclear. A quantification of this effect is required for the rational design of PGM-free cathode electrodes, whereby the following three points would be of major interest: (1) The values of PGM-free catalysts vary widely, so that in a comparative study catalysts with high and low should be investigated. (2) When preparing electrodes with PGM-free catalysts that have a high value ρe-, conductive-carbon additives are commonly added, but there is no simple diagnostic tool that could be used for optimizing the amount of additive. (3) A quantitative model to predict the cell voltage loss due to the impact of ρe- would be desired. This can be accomplished by in-situ AC impedance analysis based on a transmission line model. 5 However, owing to higher ratio of ρe- to the ionic resistivity (ρH+) in PGM-free electrodes (>0.1/1), a modified approach needs to be developed to precisely quantify the voltage losses.6 In the present work, we present small-active area (5 cm2) single-cell H2/O2 PEMFC performance (differential-flow operation) combined with in-situ AC impedance and ex-situ 4-point-probe resistance measurement in order to elucidate the impact of the electrical resistivity of PGM-free cathode catalyst layer on performance. Two different catalysts with low and high ρe- are investigated. The results indicate that the lower one shows no significant change in cell voltage upon the addition of 7.5 wt% of conductive carbon (Figure 1a). However, with same wt% of carbon additive, the cell voltage for catalyst with high ρe- can be increased by 70 mV at 1 A/cm2, resulting in a ~30% improvement in peak power density (Figure 1b). Furthermore, we will present an in-situ AC impedance technique under blocking condition (N2 feed to cathode) that we developed to quantify ρe- and ρH+ of PGM-free cathode electrodes with and without carbon additive. Using these values, the cell-voltage gains due to the reduction of ρe- of a PGM-free cathode by carbon additive can be predicted (Figure 1c). At the end, a comparison between in-situ AC-impedance and ex-situ 4-point-probe measurements for PGM-free cathode electrodes will be presented and discussed. Overall, the study not only provides a new insight and methodology for electrode optimization of PGM-free cathode catalysts, but also reveals in some cases show significant impact of electrical conductivity on fuel cell performance with PGM-free catalysts. ACKNOWLEDGEMENTS This work is supported by the Fuel Cells and Hydrogen Joint Undertaking under grant agreement No. 779550 (PEGASUS). This Joint Undertaking receives support from the European Union’s Horizon 2020 research and innovation programme, Hydrogen Europe and Hydrogen Europe Research. REFERENCE T. Thompson, A. R. Wilson, P. Zelenay, D. J. Myers, K. L. More, K. C. Neyerlin, and D. Papageorgopoulos, Solid State Ionics319, 68-79 (2018) Banham, J. -Y. Choi, T. Kishimoto, and S. Ye, Advanced Materials 31, 1804846 (2019) Malko, T. Lopes, E. A. Ticianelli, and A. Kucernak, Journal of Power Sources 323, 189-200 (2016) G. Wang, L. Osmieri, A. G. Star, J. Pfeilsticker, and K. C. Neyerlin, Journal of The Electrochemical Society 167, 044519 (2020) Liu, M. Murphy, D. Baker, W. Gu, C. Ji, J. Jorne, and H. A. Gasteiger, ECS Transactions 11, 473 (2007) Landesfeind, M. Ebner, A. Eldiven, V. Wood, and H. A. Gasteiger, Journal of The Electrochemical Society 165, 469-476 (2018) Figure 1

The high cost and the restricted availability of Platinum-Group-Metals (PGM) used in current catalysts is one of the major hurdles for the large-scale commercialization of Proton Exchange Membrane Fuel Cells (PEMFCs). In the last decade, great efforts have been made to develop efficient PGM-free catalysts for the oxygen reduction reaction (ORR), especially metal-nitrogen-doped carbons (M-N-Cs, with M = Fe, Co). The activity gap towards Pt has successfully been narrowed, now reaching the activity requirements for practical applications.1-3 For this class of catalysts, the active site is a MN4 moiety, as known from molecules such as phthalocyanines and porphyrins.4 Due to the metastability of the MN4 sites at the temperature of their pyrolytic formation, the final transition metal loading is currently limited and significant amounts of inorganic byproducts are formed. Although synthesis protocols have been successfully optimized, multiple processing steps are required, making the preparation time-consuming. In this contribution we will show that Zn2+ ions can be utilized in our novel concept of active-site imprinting, where Zn is used as template-ion in a pyrolytic process to form Zn-N-C precursor materials.5 The Zn-N-C materials presented in this work are nitrogen-doped carbons comprising ZnN4 sites, obtained with high yield and from inexpensive precursors. The active-site imprinted carbon supports possess high surface area and hierarchical porosity, which makes them structurally advantageous for catalytic applications in terms of mass transport and high accessibility of the active sites. Through a zinc-to-iron ion exchange reaction, Fe-N-C catalysts with high Fe loading are obtained at only 170 °C. Since the active-site formation by the Zn-to-Fe exchange reaction can be conducted at low temperatures, the structural properties of the Zn-N-C precursor material are retained.6 Moreover, this synthetic procedure assures the absence of the otherwise obtained harmful side-phases (e.g., iron carbide). Cryo-Mössbauer and X-ray adsorption spectroscopy, supported by calculations of the extended X-ray absorption fine structure, reveal an exclusive presence of Fe as single atoms coordinated to four nitrogen atoms, i.e., in form of the desired FeN4 moieties. Identical-location scanning transmission electron microscopy with atomic resolution is further employed to visualize the trans-metalation event. The herein obtained catalysts match the state-of-the-art electrocatalytic activity for Fe-N-C catalyts, both in a rotating disk electrode and in single cell PEMFC measurements. The novel synthesis method will be discussed regarding its advantages and disadvantages compared to the conventional pyrolytic M-N-C catalyst syntheses, with a focus on the potential to surpass the current limitations of restricted active-site density and catalyst stability. ACKNOWLEDGEMENTS: The German Federal Ministry of Economic Affairs and Energy (BMWi) is acknowledged for funding within the Verbundproject innoKA (Project No.: 03ET6096A) REFERENCES: M. Lefèvre, E. Proietti, F. Jaouen and J.-P. Dodelet, Science, 2009, 324, 71-74. R. Bashyam and P. Zelenay, Nature, 2006, 443, 63-66. H. A. Gasteiger, S. S. Kocha, B. Sompalli and F. T. Wagner, Applied Catalysis B, 2005, 56, 9-35. Q. Jia, N. Ramaswamy, U. Tylus, K. Strickland, J. Li, A. Serov, K. Artyushkova, P. Atanassov, J. Anibal, C. Gumeci, S. C. Barton, M.-T. Sougrati, F. Jaouen, B. Halevi and S. Mukerjee, Nano Energy, 2016, 29, 65-82. A. Mehmood, J. Pampel, G. Ali, H. Y. Ha, F. Ruiz-Zepeda and T.-P. Fellinger, Advanced Energy Materials, 2018, 8. D. Menga, F. Ruiz-Zepeda, L. Moriau, M. Šala, F. Wagner, B. Koyutürk, M. Bele, U. Petek, N. Hodnik, M. Gaberšček and T.-P. Fellinger, Advanced Energy Materials, 2019, 9, 1902412. Figure 1

We report the efficient productions of single- and few-layered graphene and molybdenum disulphide (MoS2) nanosheets using a surfactant-free, water-assisted liquid-phase exfoliation (LPE) of graphite and MoS2 bulk powders in N-methylpyrrolidinone (NMP). Extensive absorption spectroscopic study and materials characterizations indicate that the addition of water to NMP was not only effective on the exfoliation yields but also the stability of the colloidal dispersions of exfoliated nanosheets in the water-NMP mixed solvent upto 18 months. Detailed micro Raman spectroscopic analysis suggests the defects of the exfoliated graphene nanosheets were reduced using the developed water-assisted LPE in NMP.

Graphene nanoribbons (GNRs) are incorporated with the nanocrystals of a porphyrinic metal–organic framework, MOF-525, by solvothermally growing MOF-525 in a suspension of well-dispersed GNRs. A nanocomposite, which is composed of the MOF-525 nanocrystals interconnected by numerous one-dimensional GNRs, is successfully synthesized. Due to the excellent dispersity, uniform thin films of the MOF-525/GNR nanocomposite can be simply deposited on conducting glass substrates by using drop casting. The obtained thin film of the MOF-525/GNR nanocomposite is applied for electrochemical nitrite sensors. The MOF-525 nanocrystals serve as a high-surface-area electrocatalyst toward nitrite and the interconnected GNRs act as conductive bridges to provide facile charge transport. The thin film of the MOF-525/GNR nanocomposite thus exhibits a much better electrocatalytic activity for the oxidation of nitrite compared to the pristine MOF-525 thin film.

Simultaneous reduction and defect restoration of graphene oxide nanoribbon (GONR) via plasma-assisted chemistry is demonstrated. Hydrogen (H2) and methane (CH4) gases are continuously dissociated in a plasma to produce atomic hydrogen and carbon-containing ions and radicals carried by the gas flow to react with and remove oxygen functional groups from GONR films. Detailed material characterization confirms that the synergistic effect of simultaneous reduction and defect restoration of GONR occurred during the H2/CH4 plasma treatment. Extensive optical transmittance measurement suggests that the optical energy gap of the as-treated reduced GONR (r-GONR) can be engineered by controlling the plasma exposure time. Systematic electrical measurement indicates that the electrical conductivity of as-treated r-GONR can be enhanced after H2/CH4-plasma treatment. The unique H2/CH4-plasma reduction with characteristics of short process time, high purity, and low temperature compared with conventional thermal and chemical reductions suggests that this nonequilibrium chemical approach can be used for industrial-scale reduction of GONR and graphene oxide (GO).

In the study, rubber accelerator 3-methylthiazolidine-2-thione (MTT) was synthesized by one-step method firstly. MTT was detected and characterized by XRD, FTIR, TG-DSC. The micro-structure and intrinsic regularity were revealed. Chemical bond types into MTT molecule were revealed by FTIR. MTT phase composition and structure were given by crystallographic data from XRD detecting such as cell parameters, crystal face index. The phase composition and qualitative identification of MTT structure were completed. Two kinds of information were detected by TG-DSC as quality change and thermal effect. MTT phase transition and decomposition temperature were 76.3 and 306.9 ℃ respectively. The decomposition temperature of MTT was very high. It could provided reference with research on rubber vulcanizing properties by MTT on rubber vulcanizing machine. This study can provide the basis experimental data on the enterprises to designate the working standard tracing detection of MTT industrialized production. Performance index of MTT was judged.

Hydrogen peroxide (H 2 O 2 ) is an essential mediator for most of the oxidative biological reactions in enzyme-based biosensor systems, such as glucose oxidase, cholesterol oxidase, and alcohol oxidase. Synthesis of new catalysts to detect the concentration of H 2 O 2 more precisely is indispensable for enzyme-based electrochemical biosensors. In this study, boron-doped graphene nanosheets (BGNs) with 2.2 atomic percentage (at%) boron doping level and a hierarchical microstructure were synthesized by an atmospheric-pressure carbothermal reaction as a noble-metal free catalyst for sensing H 2 O 2 . The isolated boron atoms on the BGNs surface act as the electrocatalytic sites by transferring charges to neighbor carbon atoms, and the hierarchical microstructure provides multidimensional electron transport pathways for charge transfer and therefore enhances the electrocatalytic ability. BGNs possess a higher reduction current in the cyclic voltammetry (CV) measurement than that of pristine graphene nanosheets (GNs) over the detection range of 0.0 to 10.0 mM at −0.4 V ( vs. Ag/AgCl). The BGNs modified electrochemical sensor shows a linear range from 1.0 to 20.0 mM of H 2 O 2 with a sensitivity of 266.7 ± 3.8 μA mM −1 cm −2 and limit of detection (LOD) of 3.8 μM at a signal-to-noise (S/N) ratio of 3. The beneficial hierarchical microstructure and the synergetic effects arising from doping boron in GNs accomplish the better performance of the BGNs modified electrochemical sensor.

This article examines the development of China's automotive industry. The evidence shows that integration in global production networks has stimulated upgrading of technological capabilities among automotive firms. However, the competitiveness and intra-industry analyses show mixed results. Although intra-industry trade in automotive products has improved since 2000, the trade competitiveness of completely built-up vehicles has largely remained in low value-added activities. Nevertheless, firm-level evidence shows that the industry has undergone considerable upgrading, albeit in low value-added activities. Trade integration and host-country institutional support have been the prime driving forces of technological upgrading in the automotive industry in China.