Three-dimensional Ni2P–MoP2 mesoporous nanorods array as self-standing electrocatalyst for highly efficient hydrogen evolution

Electrochemical hydrogen evolution reaction (HER) via the splitting of water has required electrocatalysts with cost-effectiveness, environmentally friendliness, high catalytic activity, and superior stability to meet the hydrogen economy in future. In this context, we report the successful synthesis of self-standing mesoporous Ni₂P–MoP₂ nanorod arrays on nickel foam (Ni₂P–MoP₂ NRs/3D-NF) through an effective phosphidization of the corresponding NiMoO₄ NRs/3D-NF. The as-synthesis Ni₂P–MoP₂ NRs/3D-NF, as an efficient HER electrocatalyst, exhibits small overpotential of 82.2 and 124.7 mV to reach current density of 10 and 50 mA cm⁻², a low Tafel slope of 52.9 mV dec⁻¹ and it retains its catalytic performance for at least 20 h in alkaline condition. Our work also offers a new strategy in designing and using transition metal phosphide-based 3D nanoarrays catalysts with enhanced catalytic efficiency for mass production of hydrogen fuels.     

Self-supported Ni2P nanotubes coated with FeP nanoparticles electrocatalyst (FeP@Ni2P/NF) for oxygen evolution reaction

Bimetallic phosphides have been widely investigated as electrocatalysts for oxygen evolution reaction (OER) due to their efficient activity and environmental friendliness. While the reasonable design and controllable synthesis of bimetallic phosphide with typical nanostructure is still a great challenge. Hence, we put forward a novel and straightforward way for constructing FeP nanoparticles coated Ni₂P ultrathin nanotube arrays on the surface of Ni foil (FeP@Ni₂P/NF), which is synthesized through two steps of electrodeposition and subsequent in-situ phosphorization process. The obtained FeP@Ni₂P/NF shows excellent electrochemical activity for OER, and it only needs potential of 1.52 V vs. RHE to reach the current density of 50 mA cm⁻² in an alkaline media. The excellent electrocatalytic activity of FeP@Ni₂P/NF mainly benefits from: (i) the synergistic effect between FeP and Ni₂P promoting electron transfer; (ii) the formation of the unique 3D ultrathin nanotube arrays increasing the quantity of active sites and avoiding the agglomeration of catalysts during testing. In addition, the influence of reaction condition on the electrochemical activity for OER has also been investigated through altering the phosphorization temperature of precursor.     

Ternary metal sulfides MoCoNiS derived from metal organic frameworks for efficient oxygen evolution

Developing a highly active and low-cost non-precious metal electrocatalyst for oxygen evolution has been urgent for the clean energy system. Herein, the ternary metal sulfides MoCoNiS supported on nickel foam (MoCoNiS/NF) are successfully prepared using Mo doping Co-based metal-organic framework (Co-MOF) as precursor, which may be helpful for the good dispersion of different metal element. The uniform elements distribution of Mo, Co and Ni on MoCoNiS/NF is determined by all kinds of physical characterization. Mo doping may regulate the electronic environment around Co and Ni, suggesting the potential synergistic effects between different heteroatoms. Electrochemical test shows that MoCoNiS/NF exhibits the excellent OER activity than other single metal or binary metal sulfides as comparison samples, needing only 151 and 226 mV overpotential to achieve current density of 10 (η₁₀ = 151 mV) and 100 mA cm⁻² (η₁₀₀ = 226 mV), respectively. The excellent stability of MoCoNiS/NF has been achieved. The remarkable OER performance of MoCoNiS/NF may due to the synergistic effects and good electrical conductivity as well as the three-dimensional structure of NF as substrate. Therefore, the rational design of MOF derived multi transition metal-based electrocatalysts will be an effective way for increasing OER performance.     

变形铝合金表面锆基化学转化膜的研究现状

化学转化膜是金属表面主要的处理方法之一，具备良好的附着力和耐蚀性，能为铝合金提供一定的临时防护。传统的六价铬酸盐化学转化膜在日渐严苛的环保压力下已经逐渐淘汰，取而代之的是近几年发展迅猛的三价铬及无铬锆基化学转化膜。铝合金可分为铸造铝合金和变形铝合金，按照所含主要合金元素和热处理状态可分为若干个系列和型号。本文选取几种典型的变形铝合金，综述了不同铝合金微观组织对转化膜成膜过程的影响，化学转化液添加剂、预处理和后处理工艺对转化膜性能的调控及作用机理，以及几种典型商业钝化剂在变形铝合金表面的应用。总结了目前变形铝合金表面锆基化学转化膜仍面临的问题和发展趋势，未来化学转化膜需在满足新型铝合金发展要求的基础上，通过不同有机、无机添加剂以及外场作用对转化膜的成膜均一性、完整性进行调控，以提高转化膜的综合性能。     

Construction of hierarchical Prussian Blue Analogue phosphide anchored on Ni2P@MoOx nanosheet spheres for efficient overall water splitting

In response to the energy crisis, molybdenum-based catalyst has been proposed as a high-performance electrocatalytic material due to its low price and excellent HER performance. However, in contrast with its excellent HER performance, its poor OER performance often limits practical application as a high-performance overall water splitting catalyst. In this study, Prussian blue analogue (PBA) is grown in-situ on molybdenum-based nanosheet spheres by a simple and ingenious method and then subjected to phosphorization. The resulting composite catalyst exhibits highly efficient overall water splitting performance, overpotentials at current densities of 10 mA cm⁻² and 100 mA cm⁻² for the HER and OER are −61 mV and 268 mV, respectively. Moreover, an alkaline electrolyzer makes up by the catalyst both as positive and negative can reach a cell voltage 1.494 V at 10 mA cm⁻² for the overall water splitting. This method has provided a new strategy to effective combine PBA and molybdenum-based catalyst.     

A simple physical mixing method for MnO2/MnO nanocomposites with superior Zn2+ storage performance

MnO₂/MnO cathode material with superior Zn²⁺ storage performance is prepared through a simple physical mixing method. The MnO₂/MnO nanocomposite with a mixed mass ratio of 12:1 exhibits the highest specific capacity (364.2 mA·h/g at 0.2C), good cycle performance (170.4 mA·h/g after 100 cycles) and excellent rate performance (205.7 mA·h/g at 2C). Analysis of cyclic voltammetry (CV) data at various scan rates shows that both diffusion- controlled insertion behavior and surface capacitive behavior contribute to the Zn²⁺ storage performance of MnO₂/MnO cathodes. And the capacitive behavior contributes more at high discharge rates, due to the short paths of ion diffusion and the rapid transfer of electrons.     

Ethylthio-substituted sandwich phthalocyaninato europium (III) semiconductors for sensing NO2 and NH3: Effect of the extended π-conjugate systems on tuning the conductivity and sensing behavior

By using the π-conjugated phthalocyanine macrocycle as the versatile building block, a series of five sandwich-type ethylthio substituted phthalocyaninato europium complexes, namely double-decker Eu[Pc(SC₂H₅)₈]₂ (Pc-1), triple-decker Eu₂[Pc(SC₂H₅)₈]₃ (Pc-2), and their corresponding dimers, [Pc(SC₂H₅)₈]₂Eu₂[BiPc(SC₂H₅)₁₂] (Pc-1@Pc-1), [Pc(SC₂H₅)₈]₃Eu₃[BiPc(SC₂H₅)₁₂] (Pc-1@Pc-2) and [Pc(SC₂H₅)₈]₄Eu₄[BiPc(SC₂H₅)₁₂] (Pc-2@Pc-2), are synthesized and prepared into the solution-processed films by a simple quasi-Langmuir-Shäfer (QLS) method. Combination between the extending π-conjugated system in the longitudinal and transverse directions of Pc macrocycles and/or radical nature of Pc-1 unit among different semiconducting molecules result in unusually small energy gaps (0.345–0.91 eV). Consequently, all of the semiconductors exhibit excellent conductivities. Among these materials, the conductivity for the radical species Pc-1@Pc-1, Pc-1@Pc-2 and Pc-1 is about 3–4 times larger than that for the non-radical compounds Pc-2@Pc-2 and Pc-2. Moreover, the QLS films of five semiconductors take excellent linear responses for both oxidizing NO₂ (100–300 ppb) and reducing NH₃ (4–8.6 ppm). Respectively, the sensitivity (in % ppm⁻¹) gets increased in the order of Pc-1 < Pc-2 < Pc-1@Pc-1 < Pc-1@Pc-2 < Pc-2@Pc-2 for NO₂, and Pc-1@Pc-2 < Pc-1 < Pc-1@Pc-1 < Pc-2@Pc-2 < Pc-2 for NH₃. Depending on the highly extended π-conjugated systems, Pc-2@Pc-2 and Pc-2 films achieve the highest sensitivity of 208.2% ppm⁻¹ and 0.97% ppm⁻¹ to NO₂ and NH₃, respectively. In addition, with a less than 2 min response time within a limit of detection at 10 ppb for NO₂ and 0.48 ppm for NH₃, good reproducibility and selectivity have been revealed for the Pc-2@Pc-2 and Pc-2 films among the best gas sensors obtained so far for all the solution-processed films based on organic semiconductors in dry air at room temperature. More importantly, it is firstly demonstrated that the high NO₂ sensing is resulted from low Oxd₁, and high NH₃ sensing is resulted from high Red₁ among the sandwich Pc-based semiconductors.     

Spinel CoFe2O4 supported by three dimensional graphene as high-performance bi-functional electrocatalysts for oxygen reduction and evolution reaction

Spinel CoFe₂O₄ supported on three dimensional graphene (3DG) is prepared by hydrothermal reaction, which is denoted as CoFe₂O₄/3DG. The 3DG is prepared by the templated method, where coal tar pitch (CTP) and MgO are used as the carbon source and the template, respectively. The microstructure and composition of the resultant have been investigated by X-ray diffraction as well as X-ray photoelectron spectroscopy indicating the formation of spinel CoFe₂O₄ and composite of CoFe₂O₄/3DG. The multilayer structure of 3DG and CoFe₂O₄/3DG is also examined by the Raman spectra. Electrochemically, CoFe₂O₄/3DG shows high-performance half-wave potential is 0.80 V vs. RHE in O₂-saturated 0.1 M KOH, which is compared to 20 wt% Pt/C. When evaluated for OER activity, CoFe₂O₄/3DG obtains a low overpotential 1.63 V vs. RHE (at j = 10 mA cm⁻²), which is 180 mV better than 20 wt% Pt/C. Moreover, it possesses excellent durability superior to 20 wt% Pt/C.     

A dual-porosity dual-permeability model for acid gas injection process evaluation in hydrogen-carbonate reservoirs

The Pre-Caspian basin is one of the most prolific in terms of oil and gas exploration and hydrogen and carbon compounds energy production around the world. The major hydrogen and carbon compounds reservoirs are Carboniferous reef and platform hydrogen-carbonate rocks. The original fluids under subsurface conditions contain 15% hydrogen sulfide and 4% carbon dioxide. Acid hydrogen and carbon compounds reinjection is not only an environmentally friendly solution for disposal of produced greenhouse gases but also enhances oil recovery and supplies more fuel energy. On the other hand, the presence of fractures makes hydrogen-carbonate reservoir characteristics nature more complicated than conventional sandstone reservoirs, which leads to a tremendous challenge to evaluate the gas injection process. In this work, a dual-porosity dual-permeability formulation was used to model the dual-medium nature incorporating matrix system with high porosity and low permeability and fracture network with low porosity and high permeability. After matching PVT experiments, a ten pseudo-components fluid model was generated for running compositional simulation. The miscible hydrogen and carbon compounds injection was simulated as an effective enhanced oil recovery approach. Sensitivity analysis such as timing of injection gas, injection rate, well spacing and completion interval have proposed the optimal condition for the miscible hydrogen and carbon compounds flooding. The recommended optimum hydrogen and carbon compounds injection scenario is twice higher oil recovery compared with natural depletion. The results of this study illustrate further the practicability of pseudo-components splitting and lumping for compositional simulation to evaluate the performance of hydrogen and carbon compounds injection processes, and are of great importance using the dual-porosity dual-permeability method performing numerical simulation of naturally fractured hydrogen-carbonate reservoirs.     

Slow feature analysis for monitoring and diagnosis of control performance

Recently, slow feature analysis (SFA), a novel dimensionality reduction technique, has been adopted for integrated monitoring of operating condition and process dynamics. By isolating temporal behaviors from steady-state information, the SFA-based monitoring scheme enables improved discrimination of nominal operating point changes from real faults. In this study, we demonstrate that the temporal dynamics is an additional indicator of control performance changes, and further exploit its unique efficacy in control performance monitoring. Because of its data-driven nature and ease from first-principle knowledge, the SFA-based monitoring scheme allows an overall assessment of the plant-wide control performance and is compatible with different control strategies. An attractive feature of the SFA-based approach compared to existing ones is that generic process monitoring indices are used, which renders contribution plots naturally applicable to real-time diagnosis of control performance. As a result, potential fault variables as root causes of control performance changes can be identified, including not only controlled variables (CV) but also manipulated variables (MV) and disturbance variables (DV). Simulated and experimental studies demonstrate the effectiveness of the proposed method.