MXene based non-noble metal catalyst for overall water splitting in alkaline conditions

MXene,the two-dimensional transition metal carbide or nitride material,was first discovered in 2011.They possess superior characteristics such as stability,electric conductivity,and electrochemical properties,that make them attract the attention of the energy engineering field.Overall water splitting which generates hydrogen and oxygen,not only serves as a clean energy supply technology but also demonstrates the capacity for redistribution and integration of renewable energy.MXene based non-noble metal has demonstrated significant potential in terms of cost-effectiveness.Therefore,the current focus is implementing targeted regulation at the micro level to render it effective comparable to the precious metals.In this context,the mechanisms of the hydrogen evolution reaction(HER) and the oxygen evolution reaction(OER) under the influence of MXene can be elucidated in terms of electron and ion transfer processes,hydrogen coverage,and regulation of terminal groups.Certainly,the composition,structure,synthesis,and stability strategies of MXene are the subjects of comprehensive investigation from both theoretical calculations using density functional theory(DFT) and experimental perspectives.In addition,this review provides a comprehensive summary of MXene based non-noble metal and various modification methods.These methods encompass doping,vacancy engineering,hybrid structures,heterojunction formation,multi-scale engineering,surface engineering,and phase engineering.The review also presents suggestions for designing high-performance MXene based on non-noble metals.It offers guidance on employing construction strategies for electrocatalysts.By leveraging the unique properties and tunability of MXene and implementing these modification methods,researchers can enhance the catalytic activity,stability,selectivity,and efficiency of MXene based non-noble metal catalysts.

Methanol Tolerant Non-noble Metal Co-C-N Catalyst for Oxygen Reduction Reaction Using Urea as Nitrogen Source

A non-noble metal oxygen reduction reaction （ORR） catalyst labeled as Co-C-N（800） was synthesized by heat-treating a mixture of urea, cobalt chloride and acetylene black for 2 h at 800 ℃ in an inert nitrogen atmosphere. X-ray diffraction pattern indicates that a metallic β-Co is generated after the heat-treating process. The results from cyclic voltammograms show that the obtained Co-C-N（800） catalyst has good ORR catalytic activity in 0.5 mol/L H2SO4 solution. The catalyst is also good at methanol tolerance and stability in the acidic solution.

Recent Advances on MOF Derivatives for Non-Noble Metal Oxygen Electrocatalysts in Zinc-Air Batteries

Oxygen electrocatalysts are of great importance for the air electrode in zinc-air batteries(ZABs).Owing to the high specific surface area,controllable pore size and unsaturated metal active sites,metal-organic frameworks(MOFs)derivatives have been widely studied as oxygen electrocatalysts in ZABs.To date,many strategies have been developed to generate efficient oxygen electrocatalysts from MOFs for improving the performance of ZABs.In this review,the latest progress of the MOF-derived non-noble metal-oxygen electrocatalysts in ZABs is reviewed.The performance of these MOF-derived catalysts toward oxygen reduction,and oxygen evolution reactions is discussed based on the categories of metal-free carbon materials,single-atom catalysts,metal cluster/carbon composites and metal compound/carbon composites.Moreover,we provide a comprehensive overview on the design strategies of various MOF-derived non-noble metal-oxygen electrocatalysts and their structure-performance relationship.Finally,the challenges and perspectives are provided for further advancing the MOF-derived oxygen electrocatalysts in ZABs.

Recent Progress in Carbon-based Materials of Non-Noble Metal Catalysts for ORR in Acidic Environment

Proton exchange membrane fuel cell(PEMFC)has important implications for the success of clean transportation in the future.One of the key factors affecting the cost and performance of PEMFC is the cathode electrocatalyst for the oxygen reduction reaction(ORR)to overcome sluggish kinetics and instability in an acidic environment.As an essential component of the electrocatalyst,the support material largely determines the activity,mass transfer,charge transfer,and durability of the electrocatalyst.Thereby,the support material plays a critical role in the overall performance of the electrocatalyst.Carbonbased materials are widely used as electrocatalyst supports because of their high porosity,conductivity,chemical stability,and tunable morphology.Recently,some new carbon-based materials with excellent structure have been introduced,such as carbon nanotubes,carbon nanowires,graphene,metal-organic framework(MOF)-derived carbon,and biomass-derived carbon materials.Combined with a variety of strategies,such as controllable construction of porous structures and surface defects,proper doping heteroatoms,the ingenious design of model electrocatalysts,and predictive theoretical calculation,a new reliable path was provided for further improving the performance of electrocatalysts and exploring the catalytic mechanism.Based on the topic of carbon-based materials for ORR in acidic medium,this review summarizes the up-to-date progress and breakthroughs,highlights the factors affecting the catalytic activity and stability of ORR electrocatalysts in acids,and discusses their future application and development.

Catalytic effect in lithium metal batteries: From heterogeneous catalyst to homogenous catalyst

Lithium metal batteries are regarded as prominent contenders to address the pressing needs owing to the high theoretical capacity.Toward the broader implementation,the primary obstacle lies in the intricate multi-electron,multi-step redox reaction associated with sluggish conversion kinetics,subsequently giving rise to a cascade of parasitic issues.In order to smooth reaction kinetics,catalysts are widely introduced to accelerate reaction rate via modulating the energy barrier.Over past decades,a large amount of research has been devoted to the catalyst design and catalytic mechanism exploration,and thus the great progress in electrochemical performance has been realized.Therefore,it is necessary to make a comprehensive review toward key progress in catalyst design and future development pathway.In this review,the basic mechanism of lithium metal batteries is provided along with corresponding advantages and existing challenges detailly described.The main catalysts employed to accelerate cathode reaction with emphasis on their catalytic mechanism are summarized as well.Finally,the rational design and innovative direction toward efficient catalysts are suggested for future application in metal-sulfur/gas battery and beyond.This review is expected to drive and benefit future research on rational catalyst design with multi-parameter synergistic impacts on the activity and stability of next-generation metal battery,thus opening new avenue for sustainable solution to climate change,energy and environmental issues,and the potential industrial economy.

Decorating non-noble metal plasmonic Al on a TiO2/Cu2O photoanode to boost performance in photoelectrochemical water splitting

Designing low-cost and high-performance photoelectrodes with improved light harvesting and charge separation rates is significant in photoelectrochemical water splitting.Here,a novel TiO2/Cu2O/Al/Al2O3 photoelectrode is manufactured by depositing plasmonic nanoparticles of the non-noble metal Al on the surface of a TiO2/Cu2O core/shell heterojunction for the first time.The Al nanoparticles,which exhibit a surface plasmon resonance(SPR)effect and are substantially less expensive than noble metals such as Au and Ag,generate hot electron-hole pairs and amplify the electromagnetic field at the interface under illumination.The as-prepared TiO2/Cu2O/Al/Al2O3 photoelectrodes have an extended absorption range and enhanced carrier separation and transfer.Their photocurrent density of 4.52 mA·cm^-2 at 1.23 V vs.RHE represents an 1.84-fold improvement over that of TiO2/Cu2O.Specifically,the ultrathin Al2O3 passivation layer spontaneously generated on the surface of Al in air could act as a protective layer to significantly increase its stability.In this work,the synergistic effect of the heterojunctions and the SPR effect of the non-noble metal Al significantly improve the photoelectrode performance,providing a novel concept for the design of electrodes with good properties and high practicability.

Advancements in transition bimetal catalysts for electrochemical 5-hydroxymethylfurfural(HMF) oxidation

The electrochemical oxidation of 5-hydroxymethylfurfural(HMF) represents a significant avenue for sustainable chemical synthesis, owing to its potential to generate high-value derivatives from biomass feedstocks. Transition metal catalysts offer a cost-effective alternative to precious metals for catalyzing HMF oxidation, with transition bimetallic catalysts emerging as particularly promising candidates. In this review, we delve into the intricate reaction pathways and electrochemical mechanisms underlying HMF oxidation, emphasizing the pivotal role of transition bimetallic catalysts in enhancing catalytic efficiency. Subsequently, various types of transition bimetallic catalysts are explored, detailing their synthesis methods and structural modulation strategies. By elucidating the mechanisms behind catalyst modification and performance enhancement, this review sets the stage for upcoming advancements in the field, ultimately advancing the electrochemical HMF conversion and facilitating the transition towards sustainable chemical production.

A Review on Engineering Transition Metal Compound Catalysts to Accelerate the Redox Kinetics of Sulfur Cathodes for Lithium–Sulfur Batteries

Engineering transition metal compounds(TMCs)catalysts with excellent adsorption-catalytic ability has been one of the most effec-tive strategies to accelerate the redox kinetics of sulfur cathodes.Herein,this review focuses on engineering TMCs catalysts by cation doping/anion doping/dual doping,bimetallic/bi-anionic TMCs,and TMCs-based heterostructure composites.It is obvious that introducing cations/anions to TMCs or constructing heterostructure can boost adsorption-catalytic capacity by regulating the electronic structure including energy band,d/p-band center,electron filling,and valence state.Moreover,the elec-tronic structure of doped/dual-ionic TMCs are adjusted by inducing ions with different electronegativity,electron filling,and ion radius,resulting in electron redistribution,bonds reconstruction,induced vacancies due to the electronic interaction and changed crystal structure such as lat-tice spacing and lattice distortion.Different from the aforementioned two strategies,heterostructures are constructed by two types of TMCs with different Fermi energy levels,which causes built-in electric field and electrons transfer through the interface,and induces electron redistribution and arranged local atoms to regulate the electronic structure.Additionally,the lacking studies of the three strategies to comprehensively regulate electronic structure for improving catalytic performance are pointed out.It is believed that this review can guide the design of advanced TMCs catalysts for boosting redox of lithium sulfur batteries.

The effect of the carbon components on the performance of carbonbased transition metal electrocatalysts for the hydrogen evolution reaction

The hydrogen evolution reaction(HER)is a promising way to produce hydrogen,and the use of non-precious metals with an excellent electrochemical performance is vital for this.Carbon-based transition metal catalysts have high activity and stability,which are important in reducing the cost of hydrogen production and promoting the development of the hydrogen production industry.However,there is a lack of discussion regarding the effect of carbon components on the performance of these electrocatalysts.This review of the literature discusses the choice of the carbon components in these catalysts and their impact on catalytic performance,including electronic structure control by heteroatom doping,morphology adjustment,and the influence of self-supporting materials.It not only analyzes the progress in HER,but also provides guidance for synthesizing high-performance carbon-based transition metal catalysts.

Exploration of Earth-Abundant Transition Metals(Fe,Co,Ni)Doped on W_(18)O_(49)System as Electrocatalysts for Urea Productiont

The conversion of inert N_(2)and CO_(2)into urea by electrocatalytic technology not only reduces the cost of urea synthesis in future,but also alleviatesthe environmental pollution problem caused by carbon emission in traditional industrial production.However,facing downside factors such as strong competitive reactions and unclear reaction mechanism,the design of high-performance urea catalysts is imminent.This study demonstrates that W_(18)O_(49)system doped heteronuclear metals(TM=Fe,Co,Ni)can effectively solve the problem of competitive adsorption between N_(2)and CO_(2)and realize the co-adsorption of N_(2)and CO_(2)at diverse sites.Their theoretical limiting voltages for urea production on TM-W_(18)O_(49)(TM=Fe,Co,Ni)systems are-0.46 V,-0.42 V and-0.52 V,respectively.The results are all lower than that of the contrastive voltage in pristine W_(18)O_(49)system(-0.91 V),further indicating the rationality and necessity of single-atom doped strategy for the co-reduction of two molecules.Specially,Co-W_(18)O_(49)can theoretically inhibit the side reactions of NRR,CO_(2)RR,and HER,which deserve future experimental exploration in future.The study suggests that doping heteronuclear metal into transition metal oxides is a feasible scheme to solve competitive adsorption and improve catalytic performance.

A novel synthesis of highly active and highly stable non-noble-nickel-modified persulfated Al_(2)O_(3)@ZrO_(2) core-shell catalysts for n-pentane isomerization

The non-noble metal modified sulfated zirconia was found easy to deactivate.Herein,highly active and highly stable non-noble core-shell Ni-S_(2)O_(8)^(2−)/Al_(2)O_(3)@ZrO_(2) catalysts(Ni-SA@Z-x,x=Al content in wt%)have been successfully prepared and investigated for n-pentane isomerization.The results showed that the core-shell Ni-SA@Z-30 provided a sustained high isopentane yield(63.1%)with little or no deactivation within 5000 min at a mild reaction pressure of 2.0 MPa,which can be attributed to the following factors:(i)carbon deposition was greatly suppressed by the large pore size and huge pore volume;(ii)the loss of sulfur entities was suppressed because the small and highly dispersed tetragonal ZrO_(2) particles can bond with the S species strongly;(iii)strong Brønsted acidity can be maintained well after the isomerization.The pore structures and acid nature of the core-shell Ni-SA@Z-x are entirely different from those of the normal structure Ni-S_(2)O_(8)^(2−)/ZrO_(2)-Al_(2)O_(3),even though the Al content and the compositions of the individual components are the same.The Al_(2)O_(3)cores endow the catalysts with high internal surface area and high mechanical strength.Meanwhile,the ZrO_(2) shell,which consists of more and smaller tetragonal ZrO_(2) particles because of the large surface area of the Al_(2)O_(3)core,promotes the formation of more stable sulfur species and stronger binding sites.

Catalytic removal of volatile organic compounds using ordered porous transition metal oxide and supported noble metal catalysts

Most of volatile organic compounds （VOCs） are harmful to the atmosphere and human health. Cata‐lytic combustion is an effective way to eliminate VOCs. The key issue is the availability of high per‐formance catalysts. Many catalysts including transition metal oxides, mixed metal oxides, and sup‐ported noble metals have been developed. Among these catalysts, the porous ones attract much attention. In this review, we focus on recent advances in the synthesis of ordered mesoporous and macroporous transition metal oxides, perovskites, and supported noble metal catalysts and their catalytic oxidation of VOCs. The porous catalysts outperformed their bulk counterparts. This excel‐lent catalytic performance was due to their high surface areas, high concentration of adsorbed oxy‐gen species, low temperature reducibility, strong interaction between noble metal and support and highly dispersed noble metal nanoparticles and unique porous structures. Catalytic oxidation of carbon monoxide over typical catalysts was also discussed. We made conclusive remarks and pro‐posed future work for the removal of VOCs.

Non-noble metals as activity sites for ORR catalysts in proton exchange membrane fuel cells (PEMFCs)

Proton exchange membrane fuel cells(PEMFCs)have great potential to become the next generation green energy technique,but their application is limited by the slow kinetics of the cathode oxygen reduction reaction(ORR)in acidic medium.Meanwhile,the high price of Pt-based catalysts,which are now widely used commercially,has raised the cost of PEMFCs.Therefore,non-noble metal ORR catalysts as alternatives to Pt-based group metals(PGM)have attracted much attention.However,there is still a big gap between the performance of non-noble metal catalysts and commercial Pt/C catalysts in acidic environment.Recently,it has been realized that the performance of catalysts is closely related to the structure of catalytically active sites.Inspired by this,in this review,we firstly introduced the development and breakthrough of non-noble metals as activity sites.We then briefly summarized their catalytic mechanisms,and put forward some suggestions on how to improve the activity and stability of non-noble metal ORR catalysts.

Influence of preparation method on performance of a metal supported perovskite catalyst for combustion of methane

A different method was employed for the preparation of a metal supported perovskite catalyst for the catalytic combustion of methane.The prepared metallic catalysts were characterized by means of X-ray diffractometer(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),and also by ultrasonic and thermal shock tests and catalytic activity.It was found that the process factors during the preparation,e.g.the preparation of the catalyst precursor and the coating slurry,the calcination te...

Efficient and Quick Inactivation of SARS Coronavirus and Other Microbes Exposed to the Surfaces of Some Metal Catalysts

Objective To study the two metal catalysts Ag/Al2O3 and Cu/Al2O3 that interdict the transmission pathway for SARS and other respiratory infectious diseases. Methods Two metal catalysts Ag/Al2O3 and Cu/Al2O3 were pressed into wafers. One hundred μL 106 TCID50/mL SARS-CoV, 100 μL 106 PFU/mL recombinant baculovirus expressing hamster’s prion protein (haPrP) protein and roughly 106 E. coli were slowly dropped onto the surfaces of the catalyst wafers and exposed for 5 and 20 min, respectively. After eluted from the surfaces of wafers, the infectivity of viruses and propagation of bacteria were measured. The expression of PrP protein was determined by Western blot. The morphological changes of bacteria were observed by electronic microscopy. Results After exposure to the catalysts surfaces for 5 and 20 min, the infectivity of SARS-CoV in Vero cells and baculovirus in Sf9 cells dropped down to a very low and undetectable level, and no colony was detected using bacteria culture method. The expression of haPrP protein reduced to 21.8% in the preparation of Sf9 cells infected with recombinant baculovirus exposed for 5 min and was undetectable exposed for 20 min. Bacterial membranes seemed to be cracked and the cytoplasm seemed to be effluent from cell bodies. Conclusion Exposures to the surfaces of Ag/Al2O3 and Cu/Al2O3 destroy the replication and propagation abilities of SARS-CoV, baculovirus and E. coli. Inactivation ability of metal catalysts needs to interact with air, utilizing oxygen molecules in air. Efficiently killing viruses and bacteria on the surfaces of the two metal catalysts has a promising potential for air-disinfection in hospitals, communities, and households.

Study on Relationship between Microstructure of Active Phase and HDS Performance of Sulfided Ni-Mo Catalysts: Effect of Metal Loading

Six Ni-Mo catalysts with different metal contents were prepared and characterized by N2 adsorption and X-ray diffi＇actometry. The active phase microstructure of these catalysts was examined by the Raman spectroscopy, temperature- programmed reduction （TPR）, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. Hydrodesulfurization （HDS） activity of catalyst samples were analyzed in a flow fixed-bed microreactor. The sulfidation degree of Mo and the length of the MoS2 slab slightly increased with the amount of metal loaded following sulfidation. This small change is attributed to polymolybdate species observed in all the oxidized catalysts. Weak metal-support interactions, as determined by the TPR technique, increased the NiSx sulfidation phase and MoS2 slab stacking. The HDS activity of the catalyst samples increased with the number of active sites. For high metal loading catalysts, their HDS activity was nearly identical because the sulfur atoms cannot easily approach active sites. This change is caused by the large number of stacked layers in the MoS2 slabs as well as the decrease in the specific surface area and pore volume of the catalyst samples with an increasing metal loading.

Transition metal-based single-atom catalysts(TM-SACs);rising materials for electrochemical CO_(2) reduction

The continuous increase of global atmospheric CO_(2) concentrations brutally damages our environment. A series of methods have been developed to convert CO_(2) to valuable fuels and value-added chemicals to maintain the equilibrium of carbon cycles. The electrochemical CO_(2) reduction reaction(CO_(2)RR) is one of the promising methods to produce fuels and chemicals, and it could offer sustainable paths to decrease carbon intensity and support renewable energy. Thus, significant research efforts and highly efficient catalysts are essential for converting CO_(2) into other valuable chemicals and fuels. Transition metal-based single atoms catalysts(TM-SACs) have recently received much attention and offer outstanding electrochemical applications with high activity and selectivity opportunities. By taking advantage of both heterogeneous and homogeneous catalysts, TM-SACs are the new rising star for electrochemical conversion of CO_(2) to the value-added product with high selectivity. In recent years, enormous research effort has been made to synthesize different TM-SACs with different M–Nxsites and study the electrochemical conversion of CO_(2) to CO. This review has discussed the development and characterization of different TMSACs with various catalytic sites, fundamental understanding of the electrochemical process in CO_(2) RR,intrinsic catalytic activity, and molecular strategics of SACs responsible for CO_(2)RR. Furthermore, we extensively review previous studies on 1 st-row transition metals TM-SACs(Ni, Co, Fe, Cu, Zn, Sn) and dual-atom catalysts(DACs) utilized for electrochemical CO_(2) conversions and highlight the opportunities and challenges.

Recent progress of precious-metal-free electrocatalysts for efficient water oxidation in acidic media

The realization of efficient oxygen evolution reaction(OER) is critical to the development of multiple sustainable energy conversion and storage technologies, especially hydrogen production via water electrolysis. To achieve the massive application of hydrogen energy and mass-scale hydrogen production from water splitting drives the pursuit of competent precious-metal-free electrocatalysts in acidic media, where the hydrogen evolution reaction(HER) is more facilitated. However, the development of high-efficient and acid-stable OER electrocatalysts, which are robust to function stably at high oxidation potentials in the acidic electrolyte, remains a great challenge. This article contributes a focused, perceptive review of the up-to-date approaches toward this emerging research field. The OER reaction mechanism and fundamental requirements for oxygen evolution electrocatalysts in acid are introduced. Then the progress and new discoveries of precious-metal-free active materials and design concepts with regard to the improvement of the intrinsic OER activity are discussed. Finally, the existing scientific challenges and the outlooks for future research directions to the fabrication of emerging, earth-abundant OER electrocatalysts in acid are pointed out.

Selective Oxidation of CO in Excess H_2 over Ru/Al_2O_3 Catalysts Modified with Metal Oxide

The Ru/Al2O3 catalysts modified with metal oxide （K20 and La2O3） were prepared v/a incipient wetness impregnation method from RuCl3.nH2O mixed with nitrate loading on Al2O3 support. The activity of catalysts was evaluated under simulative conditions for the preferential oxidation of CO （CO-PROX） from the hydrogen-rich gas streams produced by reforming gas, and the performances of catalysts were investigated by XRD and TPR. The results showed that the activity temperature of the modified catalysts Ru-K20/Al2O3 and Ru-La2O3/Al2O3 were lowered approximately 30℃ compared with pure Ru/Al2O3, and the activity temperature range was widened. The conversion of CO on Ru-K20/Al2O3 and Ru-La2O3/Al2O3 was above 99% at 140-160℃, suitable to remove CO in a hydrogen-rich gas and the selectivity of Ru-La2O3/Al2O3 was higher than that of Ru-K2O/Al2O3in the active temperature range. Slight methanation reaction was detected at 220℃ and above.

Catalytic Reduction of CO2 to CO via Reverse Water Gas Shift Reaction:Recent Advances in the Design of Active and Selective Supported Metal Catalysts

The catalytic conversion of CO2 to CO via a reverse water gas shift(RWGS)reaction followed by well-established synthesis gas conversion technologies may provide a potential approach to convert CO2 to valuable chemicals and fuels.However,this reaction is mildly endothermic and competed by a strongly exothermic CO2 methanation reaction at low temperatures.Therefore,the improvement in the low-temperature activities and selectivity of the RWGS reaction is a key challenge for catalyst designs.We reviewed recent advances in the design strategies of supported metal catalysts for enhancing the activity of CO2 conversion and its selectivity to CO.These strategies include varying support,tuning metal–support interactions,adding reducible transition metal oxide promoters,forming bimetallic alloys,adding alkali metals,and enveloping metal particles.These advances suggest that enhancing CO2 adsorption and facilitating CO desorption are key factors to enhance CO2 conversion and CO selectivity.This short review may provide insights into future RWGS catalyst designs and optimization.