Metal doped black phosphorus/molybdenum disulfide (BP/MoS2–Y (Y: Ni,Co)) heterojunctions for the photocatalytic hydrogen evolution and electrochemical nitrite sensing applications

Recently, 2D semiconductor-based heterojunctions emerge as a focal point of intensive research owing to their unique properties, including efficient charge separation and large interface areas. Herein, Ni or Co-doped black phosphorus/molybdenum disulfide (BP/MoS₂–Y (Y: Ni, Co)) heterojunctions fabricate for photocatalytic H₂ evolution and electrochemical nitrite sensor. Compared to the BP/MoS₂, the BP/MoS₂–Ni and BP/MoS₂–Co exhibit enhanced H₂ performance, as 6.4139 mmol h⁻¹ g⁻¹ and 7.4282 mmol h⁻¹ g⁻¹, respectively, in the presence of Eosin-Y (λ ≥ 420 nm). Furthermore, BP/MoS₂–Co applies as an electrocatalyst on a GCE for the electrochemical detection of nitrite. To optimize the nitrite sensing performance of BP/MoS₂–Co, the effect of the pH, amount of material, scan rates, and other conditions study in detail. The BP/MoS₂–Co displays a linear response within the range of 100–2000 μM with a detection limit of 4.1 μM for DPV. This work can offer an opportunity for hydrogen systems as well as electrochemical sensor applications.     

An overview of hydrogen generation by hydrolysis of Al and its alloys with the addition of carbon-based materials

Al and its alloys are studied extensively for hydrogen generation through water splitting. Alloying Al with metal activators such as bismuth, indium, gallium, etc., leads to the formation of micro galvanic cells during hydrolysis reaction, resulting in an improved hydrogen generation rate. Activation of Al by adding carbon-based materials such as graphite, carbon nanotubes (CNTs), graphene, etc., can instantaneously generate hydrogen at room temperature. When carbon particles are desorbed from the Al matrix during hydrolysis, new Al is exposed, resulting in an increased reaction rate. In Al-Graphite composites which form core-shell structures, H₂O molecules penetrate through the graphite layers and break down the core-shell structure during hydrolysis, and the new Al surfaces are exposed to water. It was found that Al with nano bismuth and graphene nanosheets showed better hydrogen generation rate and hydrogen yield. Graphene nanosheets control the agglomeration of Al and enhance the specific surface area for hydrolysis. During the hydrolysis of Al-CNTs composites, CNTs act as a cathode, resulting in galvanic corrosion between CNTs and the Al matrix. CNTs can also effectively control the agglomeration of Al during ball milling. Spark plasma sintered Al–Bi-CNT composites showed an enhanced hydrogen generation rate during hydrolysis. This paper presents an overview of hydrogen generation by hydrolysis of Al and its alloys, emphasising the addition of carbon-based materials such as graphite, graphene, CNTs, etc.     

Numerical investigation on combustion regulation for a stoichiometric heavy-duty natural gas engine with hydrogen addition considering knock limitation

Aiming to further improve the thermal efficiency and reduce NO_x emissions in the stoichiometric hydrogen-enriched natural gas (NG) engine, a detailed 3-D simulation model of stoichiometric operation heavy-duty NG engine is built based on the actual boundary conditions from high load bench test. The superimposed methods for knock regulation, combustion and emission control, including Miller valve timing, hydrogen volume fraction and EGR rate were proposed and investigated comprehensively. It reveals that the typically bimodal characteristic of heat release rate (HRR) curve is caused by knock, which seriously restricts the performance improvement of stoichiometric NG engine under high load condition. To predict and control the occurrence of the second peak of HHR accurately, a new parameter BI is defined. Moreover, the Miller timing with 20°CA of the intake valve late closing shows better combustion performance within the knock limit, accompanied by a slight increase in NO_x emissions. Additionally, the 5% hydrogen blend, coupled with the Miller cycle, can further enhance the indicated thermal efficiency (ITE) of the NG engine due to the stronger effects on acceleration of laminar flame propagation velocity than the promotion of end-gas auto-ignition. Besides, the great potential of EGR rate for balancing NO_x and ITE is also confirmed in the heavy-duty hydrogen-enriched NG engine adopting Miller cycle. Compared to the original indexes, combing with the regulation strategies of intake valve late closing (20°CA), hydrogen addition (5%) and EGR (17%) are proved to increase the indicated thermal efficiency by 1.89% and reduce NO_x emissions by 11.47% within the knock limit.     

Multistep kinetic study of Fe2O3 reduction by H2 based on isothermal thermogravimetric analysis data deconvolution

The multistep kinetics of Fe₂O₃ reduction by H₂ is investigated by data deconvolution in this study. The reduction process was conducted in a TGA apparatus isothermally in the temperature range of 750–950 °C. The stepwise reduction of Fe₂O₃, i.e. Fe₂O₃–Fe₃O₄, Fe₃O₄–FeO, and FeO–Fe, was successfully decoupled from each other without controlling the reduction gas atmosphere. The overlapping, as well as the reaction rate, of each reduction step can be described by the deconvoluted data with R² > 0.995 for all the tested temperatures. Based on the deconvolution, relatively stable activation energy with increasing the conversion was obtained for each step with the model-free iso-conversion method, indicating the rationality of the decoupled multistep profiles. Master plot was then applied to evaluate the suitability of kinetic models reported in the open literature. The JMA model (Avrami-Erofe'ev equation), corresponding to the nucleation and growth mechanism, was found to be most suitable for describing each reduction step. The activation energies obtained by the JMA model fitting for Fe₂O₃–Fe₃O₄, Fe₃O₄–FeO, and FeO–Fe were 10.3, 26.7, and 24.8 kJ/mol, respectively, which also agree well with the E_a obtained by the model-free method.     

Effects of H2/O2 and H2/O3 gases on PtMo/C cathode PEMFCs performance operating at different temperatures

This study reported the activity of catalysts synthesized from platinum and molybdenum alloys in different atomic ratios and used as cathode electrocatalysts in the PEMFC. The structural properties of PtMo/C and Pt/C catalysts were analyzed by XRD analysis. The composition and distribution of these alloys in Vulcan XC-72R Carbon were determined by SEM and EDX techniques. CV studies assessed electrochemical properties such as ORR and ECSA activity. The performance of PEMFC cathodes that supplied pure hydrogen and oxygen was examined using polarization curves at different temperatures. Another way to improve the cathodic reaction is to use ozone as a potent oxidizing agent. It was measured that the OCV of the H₂/O₃ PEM fuel cell was 1.60 V, much greater than the open circuit voltage of the traditional H₂/O₂ PEM fuel cell. The PtMo/C catalyst achieved its highest power density of 137 mWcm⁻² at 70 °C, 128 mWcm⁻² at 60 °C, 101 mWcm⁻² at 50 °C, and 85 mWcm⁻² at 40 °C when exposed to H₂/O₂. As the temperature of the cell was raised, it was seen that the catalyst's catalytic activity increased.The maximum power density was detected to be inversely related to the rise in temperature when ozone was used. At low current densities, however, ozone was observed to greatly boost activation polarization.     

Novel hybrid coating of TiN and carbon with improved corrosion resistance for bipolar plates of PEM water electrolysis

Surface modification of Ti based bipolar plates (BPs) could be an effective solution to prevent the formation of low-conductive oxide film, promote the corrosion resistance and electronic conductivity as well. In this work, a novel hybrid coating composed of nano-sized TiN and carbonaceous phases (TiN–C) was successfully established on a Ti substrate via a combined electrophoretic deposition and thermal treatment process. Various physiochemical characterizations revealed that the coating was uniform, and the formation of the nano-sized TiN and carbonaceous composites reduced the interfacial contact resistance significantly. The potentiodynamic and potentiostatic polarization tests indicated that the hybrid coating TiN–C prepared at 400 °C had a corrosion current density of only 1.41 μA cm⁻², which was an order of magnitude lower than that (36.02 μA cm⁻²) of the bare Ti. Furthermore, the as-prepared coating showed excellent durability in both the simulated PEMWE environment and the PEMWE cell under polarization at 1.7 V for more than 300 h.     

红土镍矿处理工艺研究现状

随着世界上硫化镍矿资源日趋枯竭以及未来镍需求量不断增长,红土镍矿将成为未来镍的主要来源,因此红土镍矿的有效处理以及高效利用对我国的经济建设有着极大的意义。红土镍矿由于其具有储量丰富、易开采、便于运输等特点,已成为研究开发的热点。本文主要从不同矿层的红土镍矿角度,介绍了当前不同红土镍矿冶炼方法和技术,概述了不同矿层的红土镍矿及其适用的冶炼工艺,分析了不同红土镍矿处理工艺的优势与不足,实现不同类型红土镍矿的综合利用。      

高原地区二甲醚燃烧器的选型研究

二甲醚作为清洁能源,不仅可以解决我国"缺油、少气"的能源现状,而且可以减少对环境的污染。二甲醚燃烧器是将二甲醚与空气中的氧气充分混合燃烧后转变为热能的装置。主要研究二甲醚燃烧器在高原地区使用时修正系数的计算过程,以及二甲醚燃烧器在高原地区的选型方法。为二甲醚燃烧器在高原地区的应用提供了理论基础。     

摩擦对水力机组大波动过渡过程影响研究

运用MATLAB/Simulink软件对考虑摩擦和不考虑摩擦时一台水力机组在额定工况下甩负荷运行后的大波动过渡过程的仿真结果进行了比较,讨论了摩擦对电站甩负荷后的蜗壳末端水击压力、尾水管末端转速及水轮机真空度等因素的影响,进而为水电站在大波动调保计算时是否考虑摩擦的影响提供一定程度的参考.理论分析表明,摩擦对大波动过渡过程存在一定影响,但是在一定条件下,这种影响可忽略.仿真结果表明,不考虑摩擦时的水击压力和转速都略大于考虑摩擦时的水击压力和转速.对实际工程而言,这种偏大的计算结果是安全的.     

Assessment of the catalytic effect of various biomass ashes on CO2 gasification of tire char

The aim of this study was to determine the effect of various biomass ashes, comprising catalytically active components, on tire char reactivity during the CO₂ gasification process. Ashes from the combustion of corn cobs, beet pulp, sunflower husks and beech chips were selected for the research. Moreover, industrial fly ash from a coal-fired power plant was used as a reference. The tire char-ash blends with different ash contents (0–15 wt%) were gasified in the CO₂ atmosphere under non-isothermal conditions using dynTHERM Rubotherm thermobalance. Based on the n-order Coats and Redfern method, gasification reactivity indicators and kinetics parameters were calculated. The results showed that the addition of biomass ashes enhanced reactivity of tire char, and the magnitude of these changes depended on both the quantity and type of the additive. With the increase in the amount of added biomass ashes, the catalytic effect increased, and their efficiency can be ranked as follows: sunflower husk ash > corn cobs ash ≅ beet pulp ash > beech chips ash. In turn, reference fly ash from a power plant slightly affected the CO₂ gasification of tire char, regardless of its amount. Moreover, a statistically significant correlation between the reactivity indicator and the amount of K₂O, MgO and P₂O₅ in ashes analysed has been proved (reactivity indicator improved with an increase in these components amount). The performed analysis provides valuable information regarding the composition of catalysts characterised by high catalytic activity in the tire char gasification process.