Showing papers by "Nankai University published in 2022"

Enhancement of persulfate activation by Fe-biochar composites: Synergism of Fe and N-doped biochar

Abstract: Persulfate-based (PS-based) advanced oxidation process is a promising technology for degradation of organic pollutants. PS activation needs efficient and economical catalysts and heterogeneous Fe-carbon composites are competitive. Herein, novel N-doped biochar-loaded nanoscale zero-valent iron (nZVI) composites (Fe@N-BC) were synthesized and evaluated for PS activation. Detailed characterization data indicated that graphitic and pyridine N structures were introduced by N-doping, which enhanced the anchoring, dispersion and loading of amorphous nZVI on biochar. Remarkably, the optimized Fe@N-BC material, Fe@N2-BC900, presented excellent catalytic performance for PS activation for lindane removal. The N-doped defects in biochar acted as reactive bridges and accelerated the electron transfer between nZVI and PS, showing strong synergistic effects toward nZVI. O 2 • − and 1O2 were the dominant active species in catalytic systems. Additionally, Fe@N2-BC900 catalyst showed effectiveness over a wide pH range for lindane removal. This work provides a new approach to the rational design and application of Fe@N-BC for persulfate activation in pollution control, which is certified by deep exploration of reaction mechanism.

Near‐Infrared Materials: The Turning Point of Organic Photovoltaics

Abstract: Near-infrared (NIR)-absorbing organic semiconductors have opened up many exciting opportunities for organic photovoltaic (OPV) research. For example, new chemistries and synthetical methodologies have been developed; especially, the breakthrough Y-series acceptors, originally invented by our group, specifically Y1, Y3, and Y6, have contributed immensely to boosting single-junction solar cell efficiency to around 19%; novel device architectures such as tandem and transparent organic photovoltaics have been realized. The concept of NIR donors/acceptors thus becomes a turning point in the OPV field. Here, the development of NIR-absorbing materials for OPVs is reviewed. According to the low-energy absorption window, here, NIR photovoltaic materials (p-type (polymers) and n-type (fullerene and nonfullerene)) are classified into four categories: 700-800 nm, 800-900 nm, 900-1000 nm, and greater than 1000 nm. Each subsection covers the design, synthesis, and utilization of various types of donor (D) and acceptor (A) units. The structure-property relationship between various kinds of D, A units and absorption window are constructed to satisfy requirements for different applications. Subsequently, a variety of applications realized by NIR materials, including transparent OPVs, tandem OPVs, photodetectors, are presented. Finally, challenges and future development of novel NIR materials for the next-generation organic photovoltaics and beyond are discussed.

Biomedical polymers: synthesis, properties, and applications

Abstract: Biomedical polymers have been extensively developed for promising applications in a lot of biomedical fields, such as therapeutic medicine delivery, disease detection and diagnosis, biosensing, regenerative medicine, and disease treatment. In this review, we summarize the most recent advances in the synthesis and application of biomedical polymers, and discuss the comprehensive understanding of their property-function relationship for corresponding biomedical applications. In particular, a few burgeoning bioactive polymers, such as peptide/biomembrane/microorganism/cell-based biomedical polymers, are also introduced and highlighted as the emerging biomaterials for cancer precision therapy. Furthermore, the foreseeable challenges and outlook of the development of more efficient, healthier and safer biomedical polymers are discussed. We wish this systemic and comprehensive review on highlighting frontier progress of biomedical polymers could inspire and promote new breakthrough in fundamental research and clinical translation.

Orthoquinone–Based Covalent Organic Frameworks with Ordered Channel Structures for Ultrahigh Performance Aqueous Zinc–Organic Batteries

Abstract: Elaborate molecular design on cathodes is of great importance for rechargeable aqueous zinc-organic batteries' performance elevation. Herein, we design a novel orthoquinone-based covalent organic framework with an ordered channel structures (BT-PTO COF) cathode for an ultrahigh performance aqueous zinc-organic battery. The ordered channel structure facilitates ions transfer and makes the COF follow a redox pseudocapacitance mechanism. Thus, it delivers a high reversible capacity of 225 mAh g-1 at 0.1 A g-1 and an exceptional long-term cyclability (retention rate 98.0 % at 5 A g-1 (≈18 C) after 10 000 cycles). Moreover, a co-insertion mechanism with Zn2+ first followed by two H+ is uncovered for the first time. Significantly, this co-insertion behaviour evolves to more H+ insertion routes at high current density and gives the COF ultra-fast kinetics thus it achieves unprecedented specific power of 184 kW kg-1(COF) and a high energy density of 92.4 Wh kg-1(COF) . Our work reports a superior organic material for zinc batteries and provides a design idea for future high-performance organic cathodes.

An Output Feedback Approach for Regulation of 5-DOF Offshore Cranes With Ship Yaw and Roll Perturbations

Abstract: In practice, offshore cranes are effective transportation tools used on ships. Different from land-fixed cranes, offshore cranes work in the noninertial frame, which are usually affected by different disturbances. Therefore, the control problem of offshore cranes is much more difficult . Till now, only few control methods have been proposed for offshore cranes, which are usually designed for planar offshore cranes, while the more practical three-dimensional (3-D) movements are ignored . Considering these facts, in this article, we focus on the control problem of a 5 degrees of freedom (DOF) offshore crane in 3-D space with persistent ship yaw and roll perturbations and propose an effective output feedback control method. Specifically, we first present an elaborate coordinate transformation method to deal with ship perturbations. Then an energy-like function is constructed based on the transformed model, and then by designing some auxiliary signals, an output feedback method is designed with rigorous mathematical analysis to prove the closed-loop asymptotic stability results. As far as we know, the proposed method is the first control method designed for 5-DOF offshore cranes without any linearization, which only uses output signals. Finally, experimental results are included to verify the performance of the proposed method.

Electrochemical CO2 reduction in membrane-electrode assemblies

Abstract: CO2 electrochemical reduction reaction (CO2RR) enables conversion of greenhouse gas CO2 into value-added products, which simultaneously reduces carbon emissions and reduces the usage of fossil fuels as feed materials to produce fuel/chemical products. It also provides the potential to integrate electrocatalytic processes with electricity from renewable sources for storing renewable energy. Membrane-electrode assemblies (MEAs) can be an efficient solution to address the key issues in aqueous electrolyzer design and enable the industrial scale-up. In this paper, we reviewed recent advances in the experimental design and simulation of MEAs. The discussion of existing challenges and future research priorities for guiding MEA development and understanding reaction mechanism is also provided. Electrochemical conversion of gaseous CO2 to value-added products and fuels is a promising approach to achieve net-zero CO2 emission energy systems. Significant efforts have been achieved in the design and synthesis of highly active and selective electrocatalysts for this reaction and their reaction mechanism. To perform an efficient conversion and desired product selectivity in practical applications, we need an active, cost-effective, stable, and scalable electrolyzer design. Membrane-electrode assemblies (MEAs) can be an efficient solution to address the key challenges in the aqueous gas diffusion electrodes (GDE), e.g., ohmic resistances and complex reactor design. This review presents a critical overview of recent advances in experimental design and simulation of MEAs for CO2 reduction reaction, including the shortcomings and remedial strategies. In the last section, the remaining challenges and future research opportunities are suggested to support the advancement of CO2 electrochemical technologies. Electrochemical conversion of gaseous CO2 to value-added products and fuels is a promising approach to achieve net-zero CO2 emission energy systems. Significant efforts have been achieved in the design and synthesis of highly active and selective electrocatalysts for this reaction and their reaction mechanism. To perform an efficient conversion and desired product selectivity in practical applications, we need an active, cost-effective, stable, and scalable electrolyzer design. Membrane-electrode assemblies (MEAs) can be an efficient solution to address the key challenges in the aqueous gas diffusion electrodes (GDE), e.g., ohmic resistances and complex reactor design. This review presents a critical overview of recent advances in experimental design and simulation of MEAs for CO2 reduction reaction, including the shortcomings and remedial strategies. In the last section, the remaining challenges and future research opportunities are suggested to support the advancement of CO2 electrochemical technologies. The availability and affordability of fossil fuels are the key issues for society in the present and future. Using fossil fuels also causes carbon emission problems. There is an increasingly urgent need to decouple carbon emissions from economic activity without stifling growth.1Chu S. Majumdar A. Opportunities and challenges for a sustainable energy future.Nature. 2012; 488: 294-303Google Scholar, 2Lackner K.S. Climate change. A guide to CO2 sequestration.Science. 2003; 300: 1677-1678Google Scholar, 3Otto A. Grube T. Schiebahn S. Stolten D. Closing the loop: captured CO2 as a feedstock in the chemical industry.Energy Environ. Sci. 2015; 8: 3283-3297Google Scholar, 4Müller L.J. Kätelhön A. Bringezu S. McCoy S. Suh S. Edwards R. Sick V. Kaiser S. Cuéllar-Franca R. El Khamlichi A. et al.The carbon footprint of the carbon feedstock CO2.Energy Environ. Sci. 2020; 13: 2979-2992Google Scholar Electrochemical technologies for producing essential global commodities, such as chemicals, liquid fuels, and fertilizers, from gases such as CO2, CH4, or N2 are emerging as clean and viable processes that could compete economically with fossil fuel-driven processes (Figure 1).5Chen J.G. Crooks R.M. Seefeldt L.C. Bren K.L. Bullock R.M. Darensbourg M.Y. Holland P.L. Hoffman B. Janik M.J. Jones A.K. et al.Beyond fossil fuel-driven nitrogen transformations.Science. 2018; 360: eaar6611Google Scholar,6Sharifian R. Wagterveld R.M. Digdaya I.A. Xiang C. Vermaas D.A. Electrochemical carbon dioxide capture to close the carbon cycle.Energy Environ. Sci. 2021; 14: 781-814Google Scholar Attractive characteristics of electrochemical processes include modular designs, near-ambient operating pressures and temperatures, and the potential to integrate electrocatalytic processes with electricity from renewable sources (e.g., wind and solar). These attributes could enable less-centralized and more sustainable manufacturing industries decoupled from fossil fuels combustion and potentially provide efficient and versatile platforms to store renewable energy in chemicals, H2, or hydrocarbon fuels.7Service R.F. Ammonia—a renewable fuel made from sun, air, and water—could power the globe without carbon.Science. 2018; 12https://www.science.org/content/article/ammonia-renewable-fuel-made-sun-air-and-water-could-power-globe-without-carbonGoogle Scholar These electrochemical conversions could be profitable in locations with an abundant supply of renewable energy (e.g., Northern Europe, which has an oversupply of renewable energy at times) and markets for chemical products. Electrochemical reduction of CO2 to chemical feedstocks has particular attractions.8Sun Z. Ma T. Tao H. Fan Q. Han B. Fundamentals and challenges of electrochemical CO2 reduction using two-dimensional materials.Chem. 2017; 3: 560-587Google Scholar, 9Hu F. Abeyweera S.C. Yu J. Zhang D. Wang Y. Yan Q. Sun Y. Quantifying electrocatalytic reduction of CO2 on twin boundaries.Chem. 2020; 6: 3007-3021Google Scholar, 10Veenstra F.L.P. Ackerl N. Martín A.J. Pérez-Ramírez J. Laser-microstructured copper reveals selectivity patterns in the electrocatalytic reduction of CO2.Chem. 2020; 6: 1707-1722Google Scholar, 11Zhang X. Liu Y. Zhang M. Yu T. Chen B. Xu Y. Crocker M. Zhu X. Zhu Y. Wang R. et al.Synergy between β-Mo2C nanorods and non-thermal plasma for selective CO2 reduction to CO.Chem. 2020; 6: 3312-3328Google Scholar, 12Liu C. Wu Y. Sun K. Fang J. Huang A. Pan Y. Cheong W.-C. Zhuang Z. Zhuang Z. Yuan Q. et al.Constructing FeN4/graphitic nitrogen atomic interface for high-efficiency electrochemical CO2 reduction over a broad potential window.Chem. 2021; 7: 1297-1307Google Scholar, 13Zhu C. Zhang Z. Zhong L. Hsu C.-S. Xu X. Li Y. Zhao S. Chen S. Yu J. Chen S. et al.Product-specific active site motifs of Cu for electrochemical CO2 reduction.Chem. 2021; 7: 406-420Google Scholar On the one hand, it reduces the amount of CO2 being released to the atmosphere, complementing other CO2 emission reduction strategies such as CO2 capture and storage;14Naims H. Economics of carbon dioxide capture and utilization—a supply and demand perspective.Environ. Sci. Pollut. Res. Int. 2016; 23: 22226-22241Google Scholar on the other hand, the electrochemical CO2 reduction reaction (CO2RR) produces a variety of essential chemicals that used to be from petroleum, including CO (e.g., producing many liquid hydrocarbons via Fischer-Tropsch process), formate, methanol, methane, and other longer chain hydrocarbons. In the typical electrolysis cell, CO2 is reduced at the cathode, and water is oxidized at the anode. The cathode and the anode chamber are typically separated by a separator or polymeric ion exchange membrane (e.g., Nafion).15Delacourt C. Ridgway P.L. Kerr J.B. Newman J. Design of an electrochemical cell making syngas (CO+H2)from CO2and H2O reduction atroom temperature.J.Electrochem .Soc. 2008; 155: B42-B49Google Scholar Catholytes choices can be aqueous solutions of inorganic salts (e.g., KHCO3),16Yang H.B. Hung S.-F. Liu S. Yuan K. Miao S. Zhang L. Huang X. Wang H.-Y. Cai W. Chen R. et al.Atomically dispersed Ni(I) as the active site for electrochemical CO2 reduction.Nat. Energy. 2018; 3: 140-147Google Scholar ionic liquids (e.g., 1-ethyl-3-methylimidazolium tetrafluoroborate),17Rosen B.A. Salehi-Khojin A. Thorson M.R. Zhu W. Whipple D.T. Kenis P.J.A. Masel R.I. Ionic liquid-mediated selective conversion of CO2 to CO at low overpotentials.Science. 2011; 334: 643-644Google Scholar and organic solvents (e.g., acetonitrile).18Smieja J.M. Sampson M.D. Grice K.A. Benson E.E. Froehlich J.D. Kubiak C.P. Manganese as a substitute for rhenium in CO2 reduction catalysts: the importance of acids.Inorg. Chem. 2013; 52: 2484-2491Google Scholar The main reaction for focus in the electrolysis cell is the cathode CO2RR, CO2 reduction mainly occurs within a gas-liquid-solid triple-phase reaction boundary. The energy efficiency is insufficient to be economically competitive, due to the limited mass transfer, product selectivity and high cell voltages at high rates, including high ohmic loss, and electrode overpotentials. An adequate supply of gas reactants to the catalyst surface becomes more crucial at higher current densities to maintain a high reaction rate. The selectivity of CO2RR is highly dependent on catalyst materials and the triple-phase reaction microenvironment. Most of the current research focuses on catalyst material rather than mass transfer or microenvironment. In general, the CO2 mass transportation is limited by its solubility in catholyte solutions. Meanwhile, the CO2 mass-transport characteristics in membrane-electrode assembly (MEA) cells or gas diffusion electrode (GDE) cells are also influenced by the reactor configuration, electrode structure, catholyte selection, and operation conditions (e.g., pH, pressure, temperature).19Garg S. Li M.R. Weber A.Z. Ge L. Li L.Y. Rudolph V. Wang G.X. Rufford T.E. Advances and challenges in electrochemical CO2 reduction processes: an engineering and design perspective looking beyond new catalyst materials.J. Mater. Chem. A. 2020; 8: 1511-1544Google Scholar These factors, in addition to catalyst materials, can have significant impacts on the reaction pathways because of their effects on the local concentrations of reactants and products. Often, the solubility and diffusion of CO2 in the electrolyte limits the rate of CO2 mass transfer and, thus, the overall reaction rate. The solubility can be increased by operating the electrochemical reactor at high pressure or switching to a more costly (and often more toxic or corrosive) solvent as the electrolyte,20Sonoyama N. Kirii M. Sakata T. Electrochemical reduction of CO2 at metal-porphyrin supported gas diffusion electrodes under high pressure CO2.Electrochem. Commun. 1999; 1: 213-216Google Scholar but a more promising approach to overcome both CO2 solubility and diffusion limitations is the GDE. The cathode in a CO2RR electrolyzer provides (1) active catalyst sites; (2) provides contact interfaces between CO2, electrolyte, and the solid catalyst; and conducts (3) electrons to the active catalyst sites. To tackle the mass transport and reaction rate limitation of the gaseous electrocatalytic reactions in the aqueous electrolytes, GDEs are proposed that can provide conjunction of a solid, liquid, and gaseous interface, the electrical conducting catalyst determines the electrochemical reaction between the liquid and the gaseous phase.21Rabiee H. Ge L. Zhang X. Hu S. Li M. Yuan Z. Gas diffusion electrodes (GDEs) for electrochemical reduction of carbon dioxide, carbon monoxide, and dinitrogen to value-added products: a review.Energy Environ. Sci. 2021; 14: 1959-2008Google Scholar,22Li M.R. Idros M.N. Wu Y.M. Garg S. Gao S. Lin R.J. Rabiee H. Li Z.H. Ge L. Rufford T.E. et al.Unveiling the effects of dimensionality of tin oxide-derived catalysts on CO2 reduction by using gas-diffusion electrodes.React. Chem. Eng. 2021; 6: 345-352Google Scholar GDEs can be distinguished from the traditional simple planar or porous electrode by how CO2 contacts with the electrolyte: with the planar or porous electrode CO2 is dissolved in the bulk electrolyte, but, in the GDE, the gas diffuses through a porous gas-diffusion layer to the electrode/electrolyte interface. Reports in the literature suggest that GDE architectures can reduce the CO2 diffusion path to the surface of the catalyst by up to 3-orders of magnitude, i.e., from ∼50 μm on a planar electrode to around 50 nm in a GDE, which enables faster current densities.23Burdyny T. Smith W.A. CO2 reduction on gas-diffusion electrodes and why catalytic performance must be assessed at commercially-relevant conditions.Energy Environ. Sci. 2019; 12: 1442-1453Google Scholar, 24Weng L.C. Bell A.T. Weber A.Z. Modeling gas-diffusion electrodes for CO2 reduction.Phys. Chem. Chem. Phys. 2018; 20: 16973-16984Google Scholar, 25Ikeda S. Ito T. Azuma K. Ito K. Noda H. Electrochemical mass reduction of carbon-dioxide using Cu-loaded gas-diffusion electrodes. 1. Preparation of electrode and reduction products.Denki Kagaku. 1995; 63: 303-309Google Scholar Therefore, GDEs for electrochemical CO2 reduction results in an order-of-magnitude increase in obtainable limiting current densities compared with planar non-GDE systems.26Rabiee H. Zhang X. Ge L. Hu S. Li M. Smart S. Zhu Z. Yuan Z. Tuning the product selectivity of Cu hollow fiber gas diffusion electrode for efficient CO2 reduction to formate by controlled surface Sn electrodeposition.ACS Appl. Mater. Interfaces. 2020; 12: 21670-21681Google Scholar, 27Rabiee H. Ge L. Zhang X. Hu S. Li M. Smart S. Zhu Z. Yuan Z. Shape-tuned electrodeposition of bismuth-based nanosheets on flow-through hollow fiber gas diffusion electrode for high-efficiency CO2 reduction to formate.Appl. Catal. B. 2021; 286: 119945Google Scholar, 28Rabiee H. Ge L. Zhang X. Hu S. Li M. Smart S. Zhu Z. Wang H. Yuan Z. Stand-alone asymmetric hollow fiber gas-diffusion electrodes with distinguished bronze phases for high-efficiency CO2 electrochemical reduction.Appl. Catal. B. 2021; 298: 120538Google Scholar Despite this improvement, there are challenges in aqueous GDE systems, e.g., significant ohmic resistances from electrolyte layers and catalyst dissolution/delamination. These issues limit the further improvement of current densities at applied overpotentials and increase the reactor design complexity for industrial implementation. MEAs, also known as “fuel cell-type,” “zero-gap,” “catholyte-free,” or “gas-phase electrolysis,29Lee W. Kim Y.E. Youn M.H. Jeong S.K. Park K.T. Catholyte-free electrocatalytic CO2 reduction to formate.Angew. Chem. Int. Ed. Engl. 2018; 57: 6883-6887Google Scholar, 30Ju H. Kaur G. Kulkarni A.P. Giddey S. Challenges and trends in developing technology for electrochemically reducing CO2 in solid polymer electrolyte membrane reactors.J. CO2 Util. 2019; 32: 178-186Google Scholar, 31Yin Z. Peng H. Wei X. Zhou H. Gong J. Huai M. Xiao L. Wang G. Lu J. Zhuang L. An alkaline polymer electrolyte CO2 electrolyzer operated with pure water.Energy Environ. Sci. 2019; 12: 2455-2462Google Scholar” can be an efficient solution to address the challenges of the aqueous GDE. The MEA design for electrochemical cells has been widely used for fuel cells and water electrolyzers. A proton exchange membrane is typically used as an electrolyte in the MEAs, and gaseous reactants (e.g., CO2) can be directly fed with no aqueous electrolyte between the electrodes. The mainstream of the catholyte is absent for the MEA, whereas the catalyst-membrane interface requires electrolytes to allow ion transport across the ion-exchange membranes. The reactions in the cathode and anode are similar to the non-MEA design. As for the main difference in the MEA design (Figure 2), the GDE and the ion-exchange membrane (e.g., Nafion) are attached as solid catholyte; in such case, gas/liquid products are collected in the feed side, and the flowing catholyte between the catalyst layer (CL) and ion-exchange membrane can be eliminated. Therefore, this membrane-based fabrication method can greatly reduce ohmic resistance and improve current density. Through modeling study, the MEA can reduce the ohmic loss from the catholyte when producing CO at high current density operation.32Weng L.-C. Bell A.T. Weber A.Z. Towards membrane-electrode assembly systems for CO2 reduction: a modeling study.Energy Environ. Sci. 2019; 12: 1950-1968Google Scholar By utilizing MEA cells in CO2RR, high current densities upward of 100 mA cm2 have been achieved, which are an order of magnitude higher than using typical aqueous architectures.33Verma S. Lu X. Ma S. Masel R.I. Kenis P.J.A. The effect of electrolyte composition on the electroreduction of CO2 to CO on Ag based gas diffusion electrodes.Phys. Chem. Chem. Phys. 2016; 18: 7075-7084Google Scholar, 34de Tacconi N.R. Chanmanee W. Dennis B.H. Rajeshwar K. Composite copper oxide–copper bromide films for the selective electroreduction of carbon dioxide.J. Mater. Res. 2017; 32: 1727-1734Google Scholar, 35Dinh C.T. Burdyny T. Kibria M.G. Seifitokaldani A. Gabardo C.M. García de Arquer F.P. Kiani A. Edwards J.P. De Luna P. Bushuyev O.S. et al.CO2 electroreduction to ethylene via hydroxide-mediated copper catalysis at an abrupt interface.Science. 2018; 360: 783-787Google Scholar For the GDEs systems and the associated electrocatalysts, there are extensive material-centric reviews published in recent years. These reviews and prospects have enriched our fundamental understanding of the catalytic mechanism, catalytic pathways, product selectivity, and control factors in these processes.19Garg S. Li M.R. Weber A.Z. Ge L. Li L.Y. Rudolph V. Wang G.X. Rufford T.E. Advances and challenges in electrochemical CO2 reduction processes: an engineering and design perspective looking beyond new catalyst materials.J. Mater. Chem. A. 2020; 8: 1511-1544Google Scholar,21Rabiee H. Ge L. Zhang X. Hu S. Li M. Yuan Z. Gas diffusion electrodes (GDEs) for electrochemical reduction of carbon dioxide, carbon monoxide, and dinitrogen to value-added products: a review.Energy Environ. Sci. 2021; 14: 1959-2008Google Scholar,36Li M. Garg S. Chang X. Ge L. Li L. Konarova M. Rufford T.E. Rudolph V. Wang G. Toward excellence of transition metal-based catalysts for CO2 electrochemical reduction: an overview of strategies and rationales.Small Methods. 2020; 4: 2000033Google Scholar, 37Nitopi S. Bertheussen E. Scott S.B. Liu X. Engstfeld A.K. Horch S. Seger B. Stephens I.E.L. Chan K. Hahn C. et al.Progress and perspectives of electrochemical CO2 reduction on copper in aqueous electrolyte.Chem. Rev. 2019; 119: 7610-7672Google Scholar, 38Fan L. Xia C. Yang F. Wang J. Wang H. Lu Y. Strategies in catalysts and electrolyzer design for electrochemical CO2 reduction toward C2+ products.Sci. Adv. 2020; 6eaay3111Google Scholar, 39Nguyen T.N. Dinh C.-T. Gas diffusion electrode design for electrochemical carbon dioxide reduction.Chem. Soc. Rev. 2020; 49: 7488-7504Google Scholar, 40Malkhandi S. Yeo B.S. Electrochemical conversion of carbon dioxide to high value chemicals using gas-diffusion electrodes.Curr. Opin. Chem. Eng. 2019; 26: 112-121Google Scholar, 41Junge Puring K. Siegmund D. Timm J. Möllenbruck F. Schemme S. Marschall R. Apfel U.-P. Electrochemical CO2 reduction: tailoring catalyst layers in gas diffusion electrodes.Adv. Sustain. Syst. 2021; 5: 2000088Google Scholar Herein, we present this critical review on MEAs and their recent advances for CO2RR application. It covers the material selection and design, mass transfer mechanisms in MEAs, and system design. The experimental findings in recent advances in MEA systems for CO2RR present the summary of design MEAs with improved activity (e.g., current density) and selectivity (e.g., faradic efficiency of targeted product). The review of modeling methods in design and performance of MEA via modeling provides the fundamental understanding of reaction mechanism and mass transfer in MEAs that contribute to the activity, selectivity, and stability in CO2RR and engineering designs for practical applications. At the end of this review, the discussion of existing challenges and future research priorities for guiding MEA development and understanding reaction mechanism is also included. The CO2RR has been mostly tested in the aqueous phase, displaying the limitations of CO2 solubility and ohmic resistance between catalysts and electrolytes. MEA CO2RR electrolyzers offer several advantages, compared with systems with flowing-electrolyte; therefore, recently researchers have developed electrolyte-free systems for efficient CO2RR.32Weng L.-C. Bell A.T. Weber A.Z. Towards membrane-electrode assembly systems for CO2 reduction: a modeling study.Energy Environ. Sci. 2019; 12: 1950-1968Google Scholar,42Lee J.-H. Lim J. Roh C.-W. Whang H.S. Lee H. Electrochemical CO2 reduction using alkaline membrane electrode assembly on various metal electrodes.J. CO2 Util. 2019; 31: 244-250Google Scholar, 43Gabardo C.M. O’Brien C.P. Edwards J.P. McCallum C. Xu Y. Dinh C.-T. Li J. Sargent E.H. Sinton D. Continuous carbon dioxide electroreduction to concentrated multi-carbon products using a membrane electrode assembly.Joule. 2019; 3: 2777-2791Google Scholar, 44Larrazábal G.O. Strøm-Hansen P. Heli J.P. Zeiter K. Therkildsen K.T. Chorkendorff I. Seger B. Analysis of mass flows and membrane cross-over in CO2 reduction at high current densities in an MEA-type electrolyzer.ACS Appl. Mater. Interfaces. 2019; 11: 41281-41288Google Scholar, 45Fujinuma N. Ikoma A. Lofland S.E. Highly efficient electrochemical CO2 reduction reaction to CO with one-pot synthesized Co-pyridine-derived catalyst incorporated in a Nafion-based membrane electrode assembly.Adv. Energy Mater. 2020; 10: 2001645Google Scholar, 46Lee W.H. Ko Y.-J. Choi Y. Lee S.Y. Choi C.H. Hwang Y.J. Min B.K. Strasser P. Oh H.-S. Highly selective and scalable CO2 to CO—electrolysis using coral-nanostructured Ag catalysts in zero-gap configuration.Nano Energy. 2020; 76: 105030https://doi.org/10.1016/j.nanoen.2020.105030Google Scholar, 47Endrődi B. Kecsenovity E. Samu A. Darvas F. Jones R.V. Török V. Danyi A. Janáky C. Multilayer electrolyzer stack converts carbon dioxide to gas products at high pressure with high efficiency.ACS Energy Lett. 2019; 4: 1770-1777Google Scholar, 48Ham Y.S. Park Y.S. Jo A. Jang J.H. Kim S.-K. Kim J.J. Proton-exchange membrane CO2 electrolyzer for CO production using Ag catalyst directly electrodeposited onto gas diffusion layer.J. Power Sources. 2019; 437: 226898Google Scholar, 49Kutz R.B. Chen Q. Yang H. Sajjad S.D. Liu Z. Masel I.R. Sustainion imidazolium-functionalized polymers for carbon dioxide electrolysis.Energy Technol. 2017; 5: 929-936Google Scholar, 50Sato M. Ogihara H. Yamanaka I. Electrocatalytic reduction of CO2 to CO and CH4 by Co–N–C catalyst and Ni co-catalyst with PEM reactor.ISIJ Int. 2019; 59: 623-627Google Scholar, 51Ogihara H. Maezuru T. Ogishima Y. Inami Y. Saito M. Iguchi S. Yamanaka I. The active center of Co–N–C electrocatalysts for the selective reduction of CO2 to CO using a Nafion-H electrolyte in the gas phase.ACS Omega. 2020; 5: 19453-19463Google Scholar, 52Oh S. Park Y.S. Park H. Kim H. Jang J.H. Choi I. Kim S.-K. Ag-deposited Ti gas diffusion electrode in proton exchange membrane CO2 electrolyzer for CO production.J. Ind. Eng. Chem. 2020; 82: 374-382Google Scholar, 53Liu Z. Yang H. Kutz R. Masel R.I. CO2 electrolysis to CO and O2 at high selectivity, stability and efficiency using sustainion membranes.J. Electrochem. Soc. 2018; 165: J3371-J3377Google Scholar, 54Xu Y. Edwards J.P. Liu S. Miao R.K. Huang J.E. Gabardo C.M. O’Brien C.P. Li J. Sargent E.H. Sinton D. Self-cleaning CO2 reduction systems: unsteady electrochemical forcing enables stability.ACS Energy Lett. 2021; 6: 809-815Google Scholar, 55Hou P. Wang X. Kang P. Membrane-electrode assembly electrolysis of CO2 to formate using indium nitride nanomaterials.J. CO2 Util. 2021; 45: 2411-2502Google Scholar, 56Díaz-Sainz G. Alvarez-Guerra M. Ávila-Bolívar B. Solla-Gullón J. Montiel V. Irabien A. Improving trade-offs in the figures of merit of gas-phase single-pass continuous CO2 electrocatalytic reduction to formate.Chem. Eng. J. 2021; 405: 126965Google Scholar, 57de Jesus Gálvez-Vázquez M. Moreno-García P. Xu H. Hou Y. Hu H. Montiel I.Z. Rudnev A.V. Alinejad S. Grozovski V. Wiley B.J. et al.Environment matters: CO2RR electrocatalyst performance testing in a gas-fed zero-gap electrolyzer.ACS Catal. 2020; 10: 13096-13108Google Scholar, 58Digdaya I.A. Sullivan I. Lin M. Han L. Cheng W.-H. Atwater H.A. Xiang C. A direct coupled electrochemical system for capture and conversion of CO2 from oceanwater.Nat. Commun. 2020; 11: 4412Google Scholar, 59Sisler J. Khan S. Ip A.H. Schreiber M.W. Jaffer S.A. Bobicki E.R. Dinh C.-T. Sargent E.H. Ethylene electrosynthesis: a comparative techno-economic analysis of alkaline vs membrane electrode assembly vs CO2–CO–C2H4 tandems.ACS Energy Lett. 2021; 6: 997-1002Google Scholar It has been reported that MEA (or zero-gap or fuel cell-like) systems show a lower resistance and cell potential due to the absence of electrolytes. In addition, pumping an electrolyte brings some complexities to the systems (e.g., pumping, purification of electrolyte, etc.), whereas electrolyte-free systems have ease of scalability and operation without any possible catalyst poisoning from the impurities of the electrolyte.19Garg S. Li M.R. Weber A.Z. Ge L. Li L.Y. Rudolph V. Wang G.X. Rufford T.E. Advances and challenges in electrochemical CO2 reduction processes: an engineering and design perspective looking beyond new catalyst materials.J. Mater. Chem. A. 2020; 8: 1511-1544Google Scholar Besides, other issues such as electrolyte consumption by CO2 and GDE flooding are effectively eliminated. Another important advantage of MEA reactors is their superior product and voltage stability as well as energy efficiency compared with electrolyte-flowing systems. MEA-type electrolyzers have not been extensively studied for multicarbon products and the formation of these products via more complex reactions requires more studies.60Sebastián D. Palella A. Baglio V. Spadaro L. Siracusano S. Negro P. Niccoli F. Aricò A.S. CO2 reduction to alcohols in a polymer electrolyte membrane co-electrolysis cell operating at low potentials.Electrochim. Acta. 2017; 241: 28-40Google Scholar Gabardo et al. used MEA electrolyzer to produce concentrated multicarbon products at industrially relevant current densities, confirming the feasibility of using MEA-type reactors to produce liquid products with high concentration.43Gabardo C.M. O’Brien C.P. Edwards J.P. McCallum C. Xu Y. Dinh C.-T. Li J. Sargent E.H. Sinton D. Continuous carbon dioxide electroreduction to concentrated multi-carbon products using a membrane electrode assembly.Joule. 2019; 3: 2777-2791Google Scholar They prepared the MEA via sputtering of Cu onto a porous polytetrafluoroethylene (PTFE) membrane. By running the reactor at a slightly elevated temperature (40°C), they achieved cathode outlet concentrations of ∼30% ethylene and the direct production of ∼4 wt % ethanol with over 100 h stability.43Gabardo C.M. O’Brien C.P. Edwards J.P. McCallum C. Xu Y. Dinh C.-T. Li J. Sargent E.H. Sinton D. Continuous carbon dioxide electroreduction to concentrated multi-carbon products using a membrane electrode assembly.Joule. 2019; 3: 2777-2791Google Scholar Recently, Gu et al. used Cu catalysts with stepped sites with high surface coverages of ∗CO intermediates and the bridge-bound ∗CO adsorption, and it allowed to trigger CO2 reduction pathways toward the formation of alcohols.61Gu Z. Shen H. Chen Z. Yang Y. Yang C. Ji Y. Wang Y. Zhu C. Liu J. Li J. et al.Efficient electrocatalytic CO2 reduction to C2+ alcohols at defect-site-rich Cu surface.Joule. 2021; 5: 429-440Google Scholar In this study, electrochemical deposition of Cu under a CO-rich environment led to the fabrication of defective Cu surfaces via stabilizing the surface energy, and the defect-site-rich surfaces greatly enhance the CO2-to-alcohol reduction pathway. Using this defect-site-rich Cu catalyst, ∼70% FE toward C2+ alcohols with partial current densities of >100 mA cm−2 was achieved. In contrast to scarce multicarbon production on MEA-type electrolyzers, CO production has been one of the main targets of studies. Production of CO by using CO-selective Au and Ag electrocatalysts has been the main application of MEA systems for CO2RR.42Lee J.-H. Lim J. Roh C.-W. Whang H.S. Lee H. Electrochemical CO2 reduction using alkaline membrane electrode assembly on various metal electrodes.J. CO2 Util. 2019; 31: 244-250Google Scholar,45Fujinuma N. Ikoma A. Lofland S.E. Highly efficient electrochemical CO2 reduction reaction to CO with one-pot synthesized Co-pyridine-derived catalyst incorporated in a Nafion-based membrane electrode assembly.Adv. Energy Mater. 2020; 10: 2001645Google Scholar,46Lee W.H. Ko Y.-J. Choi Y. Lee S.Y. Choi C.H. Hwang Y.J. Min B.K. Strasser P. Oh H.-S. Highly selective and scalable CO2 to CO—electrolysis using coral-nanostructured Ag catalysts in zero-gap configuration.Nano Energy. 2020; 76: 105030https://doi.org/10.1016/j.nanoen.2020.105030Google Scholar,48Ham Y.S. Park Y.S. Jo A. Jang J.H. Kim S.-K. Kim J.J. Proton-exchange membrane CO2 electrolyzer for CO production using Ag catalyst directly electrodeposited onto gas diffusion layer.J. Power Sources. 2019; 437: 226898Google Scholar, 49Kutz R.B. Chen Q. Yang H. Sajjad S.D. Liu Z. Masel I.R. Sustainion imidazolium-functionalized polymers for carbon dioxide electrolysis.Energy Technol. 2017; 5: 929-936Google Scholar, 50Sato M. Ogihara H. Yamanaka I. Electrocatalytic reduction of CO2 to CO and CH4 by Co–N–C catalyst and Ni co-catalyst with PEM reactor.ISIJ Int. 2019; 59: 623-627Google Scholar, 51Ogihara H. Maezuru T. Ogishima Y. Inami Y. Saito M. Iguchi S. Yamanaka I. The active center of Co–N–C electrocatalysts for the selective reduction of CO2 to CO using a Nafion-H electrolyte in the gas p

Adaptive Decentralized Asymptotic Tracking Control for Large-Scale Nonlinear Systems With Unknown Strong Interconnections

Abstract: An adaptive decentralized asymptotic tracking control scheme is developed in this paper for a class of large-scale nonlinear systems with unknown strong interconnections, unknown time-varying parameters, and disturbances. First, by employing the intrinsic properties of Gaussian functions for the interconnection terms for the first time, all extra signals in the framework of decentralized control are filtered out, thereby removing all additional assumptions imposed on the interconnections, such as upper bounding functions and matching conditions. Second, by introducing two integral bounded functions, asymptotic tracking control is realized. Moreover, the nonlinear filters with the compensation terms are introduced to circumvent the issue of “explosion of complexity”. It is shown that all the closed-loop signals are bounded and the tracking errors converge to zero asymptotically. In the end, a simulation example is carried out to demonstrate the effectiveness of the proposed approach.

New Adaptive Control Methods for $n$ -Link Robot Manipulators With Online Gravity Compensation: Design and Experiments

Abstract: For robot manipulators subject to unmeasurable/uncertain plant parameters, this article designs a new adaptive motion controller, which ensures positioning errors to converge to zero and provides accurate gravity compensation. Meanwhile, specific motion constraints are also satisfied during the entire control process. Additionally, the proposed controller is further extended to address output feedback control without velocity measurement/numerical differential operations. A useful feature of this article is that neither complicated gain constraints nor the upper/lower bounds of model parameters/matrices in the dynamics are required in controller design and analysis, which greatly facilitates practical applications. Meanwhile, by introducing a nonlinear auxiliary term (related to motion constraints and error signals) into the proposed controllers, all links accurately reach their desired positions without exceeding the preset constraints, while the gravity vector is estimated online to eliminate static errors. Additionally, the asymptotic stability of the system equilibrium point is strictly proven; more importantly, the difficulty of stability analysis is significantly decreased based on the elaborately constructed Lyapunov function candidate. Compared with existing controllers, the main merits of the designed control schemes include fewer control gain conditions, more concise closed-loop stability analysis, and higher safety satisfying specific constraints. Finally, some hardware experiments are carried out to validate the performance of the presented controllers.