Iron-group electrocatalysts for ambient nitrogen reduction reaction in aqueous media

Electrochemical nitrogen reduction reaction(NRR)is considered as an alternative to the industrial Haber-Bosch process for NH3 production due to both low energy consumption and environment friendliness.However,the major problem of electrochemical NRR is the unsatisfied efficiency and selectivity of electrocatalyst.As one group of the cheapest and most abundant transition metals,iron-group(Fe,Co,Ni and Cu)electrocatalysts show promising potential on cost and performance advantages as ideal substitute for traditional noble-metal catalysts.In this minireview,we summarize recent advances of iron-group-based materials(including their oxides,hydroxides,nitrides,sulfides and phosphides,etc.)as non-noble metal electrocatalysts towards ambient N2-to-NH3 conversion in aqueous media.Strategies to boost NRR performances and perspectives for future developments are discussed to provide guidance for the field of NRR studies.     

Double transition metal atoms anchored on Graphdiyne as promising catalyst for electrochemical nitrogen reduction reaction

Ammonia synthesis by electrochemical nitrogen reduction technique is an attractive alternative to tradi-tional Haber-Bosch process.Currently,development of an efficient and effective electrocatalyst is one of the remaining key challenges.In this work,density functional theory(DFT)computations were systemat-ically employed on double transition metal atoms(Fe,Co,Ni,Cu and Mo)anchored Graphdiyne(GDY)for nitrogen reduction reaction(NRR).The Co-Ni heteronuclear complex and Mo-Mo homonuclear complex showed the highest NRR activity while demonstrating synergistic effect of double atomic catalytic sites towards the promising NRR activity.     

Fe atoms anchored on defective nitrogen doped hollow carbon spheres as efficient electrocatalysts for oxygen reduction reaction

Defective electrocatalysts,especially for intrinsic defective carbon,have aroused a wide concern owing to high spin and charge densities.However,the designated nitrogen species favorable for creating defects by the removal of nitrogen,and the influence of defects for the coordination structure of active site and oxygen reduction reaction(ORR)activity have not been elucidated.Herein,we designed and synthesized a pair of electrocatalysts,denoted as Fe-N/C and Fe-ND/C for coordination sites of atomic iron-nitrogen and iron-nitrogen/defect configuration embedded in hollow carbon spheres,respectively,through direct pyrolysis of their corresponding hollow carbon spheres adsorbed with Fe(acac)3.The nitrogen defects were fabricated via the evaporation of pyrrolic-N on nitrogen doped hollow carbon spheres.Results of comparative experiments between Fe-N/C and Fe-ND/C reveal that Fe-ND/C shows superior ORR activity with an onset potential of 30 mV higher than that of Fe-N/C.Fe-ND sites are more favorable for the enhancement of ORR activity.Density functional theory(DFT)calculation demonstrates that Fe-ND/C with proposed coordination structure of FeN_4-x(0*intermediate and promotes the desorption of OH^*as rate-determining step for ORR in alkaline electrolyte.Thus,Fe-ND/C electrocatalysts present much better ORR activity compared with that of Fe-N/C with proposed coordination structure of FeN₄.     

Atomic CoN3S1 sites for boosting oxygen reduction reaction via an atomic exchange strategy

It is vitally important to develop high-efficiency low-cost catalysts to boost oxygen reduction reaction(ORR)for renewable energy conversion.Herein,an A-CoN3S1@...     

Construction and design principles for micro-processor-based conductometric analyzers

We consider questions connected with design of microprocessor-based conductometric analyzers and cases of the utilization of microprocessor technology to design automated instruments for analytical control.Translated from Izmeritel'naya Tekhnika, No. 11, pp. 68–70, November, 1994.     

Accidents and sociotechnical systems: principles for design

Recent industrial accident studies have noted that various organizational variables, e.g. department boundaries, management—worker communication, training programs, can have a high impact on accident occurrence. They have also noted a lack of methodology for organizational design that reflects the needs of safety. Sociotechnical systems theory is outlined as a possibly useful structure and methodology. The redesign of an underground mine is presented as a case study where safety was an important issue. Principles derived from numerous Sociotechnical designs are analyzed as to their potential applicability to safety problems.     

Electrocatalytic and photocatalytic performance of noble metal doped monolayer MoS2 in the hydrogen evolution reaction:A first principles study

To maximize the catalytic performance of MoS₂ in the hydrogen evolution reaction,we investigate the electrocatalytic and photocatalytic performance of monolayer MoS₂ doped with noble metal(Ag,Au,Cu,Pd,and Pt)using first principles calculation combined with the climbing image nudged elastic band method.We find the band gap of the monolayer MoS₂ is reduced significantly by the noble metal doping,which is unfavorable to improving its photocatalytic performance.The optical absorption coefficient shows that the doping does not increase the ability of the monolayer MoS₂ to absorb visible light.The monolayer MoS₂ doped with the noble metal is not a potential photocatalyst for the hydrogen evolution reaction because the band edge position of the conduction band minimum is lower than
-4.44 eV,the reduction potential of H⁺/H₂.Fortunately,the band gap reduction increases the electron transport performance of the monolayer MoS₂,and the activation energy of water splitting is greatly reduced by the noble metal doping,especially the Pt doping.On the whole,noble metal doping can enhance the electrocatalytic performance of the monolayer MoS₂.     

Reliability principles, methodology and methods for lifetime design

The aim of integrated lifetime design is to predict and optimise the lifetime quality of the designed facility (building, bridge, tunnel, harbour, road, railway, airport, etc.). Lifetime quality means the capability of a facility or its structures to fulfil the requirements of its users, owners and society over its entire planning and design life (usually 50–100 years). The dictating phase for optimising the lifetime quality of a facility or structure is the planning and design phase, when the degree of freedom is high, and the cost of the phase is low. Generic limit state design aims to fulfil the generic requirements of lifetime quality. At the integrated planning and design stage, performance-based and generic structural limit states design includes the following three classes: (1) Static and dynamic modelling and design against mechanical loads; (2) Durability and service life modelling and design against degrading physical, chemical and biological loads; (3) Usability and service life modelling and design against obsolescence loads. As static and dynamic design are comprehensively dealt with in the literature and in practice, this report focuses on the lifetime safety factor method for durability design and obsolescence design. Main focus of this article is in durability design. On the obsolescence design are presented only a short summary and a number of references, because this design is not much connected to materials research.     

Rational design of Fe-N-C electrocatalysts for oxygen reduction reaction:From nanoparticles to single atoms

As an alternative energy,hydrogen can be converted into electrical energy via direct electrochemical conversion in fuel cells.One important drawback of full cel...     

Solution-based synthesis and design of late transition metal chalcogenide materials for oxygen reduction reaction (ORR)

Late transition metal chalcogenide (LTMC) nanomaterials have been introduced as a promising Pt-free oxygen reduction reaction (ORR) electrocatalysts because of their low cost, good ORR activity, high methanol tolerance, and facile synthesis. Herein, an overview on the design and synthesis of LTMC nanomaterials by solution-based strategies is presented along with their ORR performances. Current solution-based synthetic approaches towards LTMC nanomaterials include a hydrothermal/solvothermal approach, single-source precursor approach, hot-injection approach, template-directed soft synthesis, and Kirkendall-effect-induced soft synthesis. Although the ORR activity and stability of LTMC nanomaterials are still far from what is needed for practical fuel-cell applications, much enhanced electrocatalytic performance can be expected. Recent advances have emphasized that decorating the surface of the LTMC nanostructures with other functional nanoparticles can lead to much better ORR catalytic activity. It is believed that new synthesis approaches to LTMCs, modification techniques of LTMCs, and LTMCs with desirable morphology, size, composition, and structures are expected to be developed in the future to satisfy the requirements of commercial fuel cells.     

Rational design of hierarchically porous Fe-N-doped carbon as efficient electrocatalyst for oxygen reduction reaction and Zn-air batteries

The rational design and construction of hierarchically porous nanostructure for oxygen reduction reaction (ORR) electrocatalysts is crucial to facilitate the exposure of accessible active sites and promote the mass/electron transfer under the gas-solid-liquid triple-phase condition. Herein, an ingenious method through the pyrolysis of creative polyvinylimidazole coordination with Zn/Fe salt precursors is developed to fabricate hierarchically porous Fe-N-doped carbon framework as efficient ORR electrocatalyst. The volatilization of Zn species combined with the nanoscale Kirkendall effect of Fe dopants during the pyrolysis build the hierarchical micro-, meso-, and macroporous nanostructure with a high specific surface area (1,586 m²·g⁻¹), which provide sufficient exposed active sites and multiscale mass/charge transport channels. The optimized electrocatalyst exhibits superior ORR activity and robust stability in both alkaline and acidic electrolytes. The Zn-air battery fabricated by such attractive electrocatalyst as air cathode displays a higher peak power density than that of Pt/C-based Zn-air battery, suggesting the great potential of this electrocatalyst for Zn-air batteries.

     

Characterization and catalytic performance of vanadium supported on sulfated Ti-PILC catalysts issued from different Ti-precursors in selective catalytic reduction of nitrogen oxide by ammonia

Vanadium supported on sulfated Ti-pillared clay catalysts (STi-PILCs) issued from different Ti-precursors were investigated for selective catalytic reduction (SCR) of NO by NH₃ in the presence of O₂. The STi-PILCs supports were prepared by hydrolysis of a series of organic or inorganic Ti-precursors; Ti(OCH₃)₄, Ti(OC₂H₅)₄, and TiCl₄ with H₂SO₄, and then modified with vanadium introduced by impregnation method. The unpromoted and promoted vanadium pillared clays were characterized using chemical analysis, N₂-physisorption, NH₃-TPD, H₂-TPR, and tested for SCR of NO by NH₃. It was found that the textural and acidic properties of the STi-PILC materials are influenced by the nature of the Ti-precursor; and the use of Ti-methoxide allows the synthesis of STi-PILC with the highest acidity. The presence of vanadium on STi-PILC supports reduces their surface areas and porous volumes, creates new redox sites, and enhances the reducibility of the sulfate groups leading to better redox properties of the binary V-STi-PILCs. After vanadium addition, the STi-PILC materials issued from Ti(OCH₃)₄, exhibited higher NO reduction activity at high temperature. These results underline the importance of the Ti-precursor for the preparation of the STi-PILC support, and the role of vanadium to increase the redox properties of V-STi-PILC catalyst for the SCR of NO by NH₃.     

碳热还原氮化法制备氮化钒合金的研究

以工业级V2O5和碳黑为原料，添加少量Fe粉为烧结助剂，经过混料，压制成块然后进行烧结，碳氮化同时反应最后制得高氮含量的致密化氮化钒合金。并利用XRD衍射仪，氧氮分析仪和密度测试等着重研究了反应温度对制备样品的相组成及其组成成分和块体密度的影响。结果表明：产品的氮含量在1100～1250℃温度范围内随着反应温度的升高而降低，而合金块体密度一直增大。     

Fundamental principles for sizing and design of gravity separators for industrial refrigeration

Throughout the past decades, the industrial refrigeration industry has developed various “rule of thumb” methods for sizing gravity liquid separators for ammonia and other common refrigerants. However, to date a uniform systematic approach or an agreeable standard has not been established. For commonly used refrigerants such as ammonia, the large installed base of separators can be used as a benchmark for sizing separators. But, when using a less common refrigerant such as CO₂, the designer faces new challenges. In this paper, a systematic approach is presented for sizing horizontal and vertical gravity liquid separators for industrial refrigeration applications. To compute separation velocities and separation distances, a theoretical model is presented. The model is used as a basis for comparison with observations from 85 operating gravity separators surveyed in the field. Criteria and formulas are presented for estimating the required liquid volume for storage. An example is provided demonstrating the use of the methods presented in this paper.     

Metrological design principles and metrological support facilities for precision oscillation sources

Translated from Izmeritel'naya Tekhnika, No. 9, pp. 47–48, September, 1990.