Non-noble metal-based catalysts for acetylene semihydrogenation:from thermocatalysis to sustainable catalysis

Selective semihydrogenation of acetylene in raw olefin streams to ethylene is a key industrial reaction to produce polymer-grade feeds for the manufacture of corresponding polymers.The currently used process in industry is the thermocatalytic acetylene semihydrogenation with pressurized hydrogen and Pd-based catalysts at relatively high temperatures.The high cost of Pd urgently desires the design of non-noble metal-based catalysts.However,non-noble metal-based catalysts commonly require much higher reaction temperatures than Pd-based catalysts because of their poor intrinsic activity.Therefore,aiming at increasing economic efficiency and sustainability,various strategies are explored for developing non-noble metal-based catalysts for thermocatalytic and green acetylene semihydrogenation processes.In this review,we systematically summarize the recent advances in catalytic technology from thermocatalysis to sustainable alternatives,as well as corresponding regulation strategies for designing high-performance non-noble metal-based catalysts.The crucial factors affecting catalytic performance are discussed,and the fundamental structure-performance correlation of catalysts is outlined.Meanwhile,we emphasize current challenging issues and future perspectives for acetylene semihydrogenation.This review will not only promote the rapid exploration of non-noble metal-based catalysts for acetylene semihydrogenation,but also advance the development of sustainable processes like electrocatalysis and photocatalysis.

Recent Advances in Transition Metal-Based Catalysts for Electrocatalytic Nitrate Reduction Reaction

The accumulation of excessive nitrate in the atmosphere not only jeopardizes human health but also disrupts the balance of the nitrogen cycle in the ecosystem.Among various nitrate removal technologies,electrocatalytic nitrate reduction reaction(eNO_(3)RR)has been widely studied for its advantages of being eco-friendly,easy to operate,and controllable under environmental conditions with renewable energy as the driving force.Transition metal-based catalysts(TMCs)have been widely used in electrocatalysis due to their abundant reserves,low costs,easy-to-regulate electronic structure and considerable electrochemical activity.In addition,TMCs have been extensively studied in terms of the kinetics of the nitrate reduction reaction,the moderate adsorption energy of nitrogen-containing species and the active hydrogen supply capacity.Based on this,this review firstly discusses the mechanism as well as analyzes the two main reduction products(N_(2)and NH_(3))of eNO_(3)RR,and reveals the basic guidelines for the design of efficient nitrate catalysts from the perspective of the reaction mechanism.Secondly,this review mainly focuses on the recent advances in the direction of eNO_(3RR)with four types of TMCs,Fe,Co,Ni and Cu,and unveils the interfacial modulation strategies of Fe,Co,Ni and Cu catalysts for the activity,reaction pathway and stability.Finally,reasonable suggestions and opportunities are proposed for the challenges and future development of eNO_(3)RR.This review provides far-reaching implications for exploring cost-effective TMCs to replace high-cost noble metal catalysts(NMCs)for eNO_(3)RR.

Metal-support interactions in designing noble metal-based catalysts for electrochemical CO_(2) reduction: Recent advances and future perspectives

Electrochemical CO_(2) reduction reaction (CO_(2) RR) offers a practical solution to current global greenhouse effect by converting excessive CO_(2) into value-added chemicals or fuels. Noble metal-based nanomaterials have been considered as efficient catalysts for the CO_(2) RR owing to their high catalytic activity, long-term stability and superior selectivity to targeted products. On the other hand, they are usually loaded on different support materials in order to minimize their usage and maximize the utilization because of high price and limited reserve. The strong metal-support interaction (MSI) between the metal and substrate plays an important role in affecting the CO_(2) RR performance. In this review, we mainly focus on different types of support materials (e.g., oxides, carbons, ligands, alloys and metal carbides) interacting with noble metal as electrocatalysts for CO_(2) RR. Moreover, the positive effects about MSI for boosting the CO_(2) RR performance via regulating the adsorption strength, electronic structure, coordination environment and binding energy are presented. Lastly, emerging challenges and future opportunities on noble metal electrocatalysts with strong MSI are discussed.

Towards the selectivity distinction of phenol hydrogenation on noble metal catalysts

Selective hydrogenation of phenol to cyclohexanone is intriguing in chemical industry.Though a few catalysts with promising performances have been developed in recent years,the basic principle for catalyst design is still missing owing to the unclear catalytic mechanism.This work tries to unravel the mechanism of phenol hydro-genation and the reasons causing the selectivity discrepancy on noble metal catalysts under mild conditions.Results show that different reaction pathways always firstly converge to the formation of cyclohexanone under mild conditions.The selectivity discrepancy mainly depends on the activity for cyclohexanone sequential hy-drogenation,in which two factors are found to be responsible,i.e.the hydrogenation energy barrier and the competitive chemisorption between phenol and cyclohexanone,if the specific co-catalyzing effect of H 2 O on Ru is not considered.Based on the above results,a quantitative descriptor,E b(one/pl)/E a,in which E a can be further correlated to the d band center of the noble metal catalyst,is proposed by the first time to roughly evaluate and predict the selectivity to cyclohexanone for catalyst screening.

Recent progress and challenges in structural construction strategy of metal-based catalysts for nitrate electroreduction to ammonia

Ammonia plays an essential role in human production and life as a raw material for chemical fertilizers.The nitrate electroreduction to ammonia reaction(NO_(3)RR)has garnered attention due to its advantages over the Haber-Bosch process and electrochemical nitrogen reduction reaction.Therefore,it represents a promising approach to safeguard the ecological environment by enabling the cycling of nitrogen species.This review begins by discussing the theoretical insights of the NO_(3)RR.It then summarizes recent advances in catalyst design and construction strategies,including alloying,structure engineering,surface engineering,and heterostructure engineering.Finally,the challenges and prospects in this field are presented.This review aims to guide for enhancing the efficiency of electrocatalysts in the NO_(3)RR,and offers insights for converting NO_(3)-to NH_(3).

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.

Perfecting HER catalysts via defects:Recent advances and perspectives

Defect engineering has become a promising approach to improve the performance of hydrogen evolution reaction(HER)catalysts.Non-noble transition metal-based catalysts(TMCs)have shown significant promise as effective alternatives to traditional platinum-group catalysts,attracting considerable attention.However,the industrial application of TMCs in electrocatalytic hydrogen production necessitates further optimization to boost both catalytic activity and stability.This review comprehensively examines the types,fabrication methods,and characterization techniques of various defects that enhance catalytic HER activity.Key advancements include optimizing defect concentration and distribution,coupling heteroatoms with vacancies,and leveraging the synergy between bond lengths and defects.In-depth discussions highlight the electronic structure and catalytic mechanisms elucidated through in-situ characterization and density functional theory calculations.Additionally,future directions are identified,exploring novel defect types,emphasizing precision synthesis methods,industrial-scale preparation techniques,and strategies to enhance structural stability and understanding the in-depth catalytic mechanism.This review aims to inspire further research and development in defect-engineered HER catalysts,providing pathways for high efficiency and cost-effectiveness in hydrogen production.

SULFUR-RESISTANT BIMETALLIC NOBLE METAL CATALYSTS FOR AROMATIC HYDROGENATION OF DIESEL FUEL

Y zeolite supporting noble metal catalysts, as the important industrial catalysts for aromatics hydrogenation, have received increasing attention in recent years. Pd M/Y bimetallic catalysts, where M is non noble metal element, were prepared to investigate the effects of the addition of a second metal. Pd M/Y catalysts were evaluated under the following conditions: H 2 pressure 4.2 MPa, MHSV 4.0 h -1 , sulfur content in feed 3000 μg/g. The microreactor results indicated that the second metal remarkably affects the hydrogenation activity of Pd/Y catalysts. Among them, Cr and W improve the sulfur resistance of Pd/Y, but La, Mn, Mo and Ag make the sulfur resistance worse and the second metals have no evident influence on product selectivity and acidic properties of the catalysts.

Electrodeposition:Synthesis of advanced transition metal-based catalyst for hydrogen production via electrolysis of water

Developing lower-cost and higher-effective catalyst to support hydrogen(H_(2))production by electrochemical water-splitting has been recognized as a preferred strategy to drive the clean energy utilization.As a credible technology for the synthesis of functional materials,electrodeposition has attracted widespread attention,especially suitable for non-noble transition metal-based catalysts(TMCs).Recently,lots of researchers have been devoted to this hot research direction with plentiful achievements,however,a comprehensive review towards this area is still missing.Hence,we summarize the past research progress,presents the technical characteristics of electrodeposition from the viewpoint of fundamental theory and influence factors for the electrochemical deposition behavior,and introduce its application in various of TMCs with versatile nanostructures and compositions.Except a deeper and more comprehensive cognition of electrodeposition,we further discuss the catalyst’s optimized hydrogen evolution reaction(HER),oxygen evolution reaction(OER)performance as well as overall water splitting that combined with the synthetic process.Finally,we conclude the technical advantages towards electrodeposition,propose challenge and future research directions in this promising field.This timely review aims to promote a deeper understanding of effective catalysts obtained via electrodeposition strategy,and provide new guidance for the design and synthesis of future catalysts for hydrogen production.

Dielectric barrier discharge plasma synthesis of Ag/γ-Al_(2)O_(3) catalysts for catalytic oxidation of CO

In this study,Ag/γ-Al_(2)O_(3)catalysts were synthesized by an Ar dielectric barrier discharge plasma using silver nitrate as the Ag source andγ-alumina(γ-Al_(2)O_(3))as the support.It is revealed that plasma can reduce silver ions to generate crystalline silver nanoparticles(Ag NPs)of good dispersion and uniformity on the alumina surface,leading to the formation of Ag/γ-Al_(2)O_(3)catalysts in a green manner without traditional chemical reductants.Ag/γ-Al_(2)O_(3)exhibited good catalytic activity and stability in CO oxidation reactions,and the activity increased with increase in the Ag content.For catalysts with more than 2 wt%Ag,100%CO conversion can be achieved at 300°C.The catalytic activity of the Ag/γ-Al_(2)O_(3)catalysts is also closely related to the size of theγ-alumina,where Ag/nano-γ-Al_(2)O_(3)catalysts demonstrate better performance than Ag/micro-γ-Al_(2)O_(3)catalysts with the same Ag content.In addition,the catalytic properties of plasma-generated Ag/nano-γ-Al_(2)O_(3)(Ag/γ-Al_(2)O_(3)-P)catalysts were compared with those of Ag/nano-γ-Al_(2)O_(3)catalysts prepared by the traditional calcination approach(Ag/γ-Al_(2)O_(3)-C),with the plasma-generated samples demonstrating better overall performance.This simple,rapid and green plasma process is considered to be applicable for the synthesis of diverse noble metal-based catalysts.

Metal-based cathode catalysts for electrocatalytic ORR in microbial fuel cells:A review

Microbial fuel cells(MFCs)have a simple structure and excellent pollutant treatment and power generation performance.However,the slow kinetics of the oxygen reduction reaction(ORR)at the MFC cathode limit power generation.The electrochemical performance of MFCs can be improved through electrocatalysis.Thus far,metal-based catalysts have shown astonishing results in the field of electrocatalysis,enabling MFC devices to demonstrate power generation capabilities comparable to those of Pt,thus showing enormous potential.This article reviews the research progress of meta-based MFC cathode ORR catalysts,including the ORR reaction mechanism of MFC,different types of catalysts,and preparation strategies.The catalytic effects of different catalysts in MFC are compared and summarized.Before discussing the practical application and expanded manufacturing of catalysts,we summarize the key challenges that must be addressed when using metal-based catalysts in MFC,with the aim of providing a scientific direction for the future development of advanced materials.

Progress in research on catalysts for catalytic oxidation of formaldehyde

Formaldehyde（HCHO）is carcinogenic and teratogenic,and is therefore a serious danger to human health.It also adversely affects air quality.Catalytic oxidation is an efficient technique for removing HCHO.The development of highly efficient and stable catalysts that can completely convert HCHO at low temperatures,even room temperature,is important.Supported Pt and Pd catalysts can completely convert HCHO at room temperature,but their industrial applications are limited because they are expensive.The catalytic activities in HCHO oxidation of transition-metal oxide catalysts such as manganese and cobalt oxides with unusual morphologies are better than those of traditional MnO2,Co3O4,or other metal oxides.This is attributed to their specific structures,high specific surface areas,and other factors such as active phase,reducibility,and amount of surface active oxygens.Such catalysts with various morphologies have great potential and can also be used as catalyst supports.The loading of relatively cheap Ag or Au on transition-metal oxides with special morphologies potentially improves the catalytic activity in HCHO removal at room temperature.The preparation and development of new nanocatalysts with various morphologies and structures is important for HCHO removal.In this paper,research progress on precious-metal and transition-metal oxide catalyst systems for HCHO oxidation is reviewed; topics such as oxidation properties,structure–activity relationships,and factors influencing the catalytic activity and reaction mechanism are discussed.Future prospects and directions for the development of such catalysts are also covered.

Noble metal-based high-entropy alloys as advanced electrocatalysts for energy conversion

Noble metal-based high-entropy alloy nanoparticles(NM-HEA NPs) have exhibited brilliant catalytic performance toward electrocatalytic energy conversion and attracted increasing attention. The near-equimolar mixed elements of NM-HEA NPs may result in the unique properties including cocktail effect, high entropy effect and lattice distortion effect, which are beneficial for improving the catalytic performance and reducing the amount of noble metal. Herein, several advanced NM-HEA NPs as electrocatalysts for energy conversion are systematically summarized. The preparation methods of NM-HEA NPs are evaluated as well as the catalytic properties and mechanism are discussed classified by electrocatalytic reactions. Finally,the challenges and prospects in this field are carefully discussed. This review provides an overview on recent advances of NM-HEA electrocatalysts for energy conversion and draws more attention in this infant research field.

Highly selective catalysts for the hydrogenation of alkynols:A review

The semi-hydrogenation of alkynols to enols is a crucial process in the production of pharmaceuticals,agrochemicals,fragrances,and flavors that involves a complex set of parallel and consecutive isomerization and hydrogenation reactions and proceeds via several key intermediates.In view of the industrial importance of large-scale enol production through alkynol hydrogenation,various noble and non-noble metal(e.g.,Ni and Pd)-based catalysts promoting this transformation have been developed.This paper reviews the design of highly selective catalysts for the semi-hydrogenation of alkynols,focusing on the role of additives,second metals,catalyst supports,and reaction conditions and combining catalytic reaction kinetics with theoretical calculations to establish the reaction mechanism and the decisive factors for boosting selectivity.Finally,a strategy for designing highly efficient and selective catalysts based on the characteristics of aqueous-phase alkynol hydrogenation is proposed.

Earth-abundant amorphous catalysts for electrolysis of water

The generation of hydrogen through the electrolysis of water has attracted attention as a promising way to produce and store energy using renewable energy sources.In this process,a catalyst is very important to achieve a high‐energy conversion efficiency for the electrolysis of water.A good catalyst for water electrolysis should exhibit high catalytic activity,good stability,low cost and good scalability.Much research has been devoted to developing efficient catalysts for both the hydrogen evolution reaction(HER)and oxygen evolution reaction(OER).Traditionally,it has been accepted that a material with high crystallinity is important to serve as a good catalyst for HER and/or OER.Recently,catalysts for HER and/or OER in the electrolysis of water splitting based on amorphous materials have received much interest in the scientific community owing to the abundant unsaturated active sites on the amorphous surface,which form catalytic centers for the reaction of the electrolysis of water.We summarize the recent advances of amorphous catalysts for HER,OER and overall water splitting by electrolysis and the related fundamental chemical reactions involved in the electrolysis of water.The current challenges confronting the electrolysis of water and the development of more efficient amorphous catalysts are also discussed.

Regeneration of single-atom catalysts deactivated under acid oxygen reduction reaction conditions

Single-atom catalysts serve as a promising candidate to realize noble-metal-free electrocatalytic oxygen reduction in acid media.However,their poor stability under working conditions strictly restrains their practical applications.Therefore,regeneration of their electrocatalytic activity is of great significance.Herein,the regeneration of a Fe-N-C single-atom catalyst is demonstrated to be feasible by a facile annealing regeneration strategy.The activity after regeneration recovers to that of the pristine electrocatalyst and surpasses the deactivated electrocatalyst.The regeneration mechanism is identified to be selfetching of the surface carbon layer and consequent exposure of the previously buried single-atom sites.Furthermore,the regeneration strategy is applicable to other single-atom catalysts.This work demonstrates the feasibility of regenerating oxygen reduction electrocatalysts and affords a pioneering approach to deal with rapid deactivation under working conditions.

Structural sensitivity of heterogeneous catalysts for sustainable chemical synthesis of gluconic acid from glucose

Gluconic acid and its derivatives have been widely used in the food and pharmaceutical industries. Conventional processes that involve the conversion of glucose into gluconic acid via fermentation present several technological shortcomings as they involve energy-intensive wastewater treatment and complex enzyme separation. Greener oxidation processes over heterogeneous metal catalysts have attracted increasing attention worldwide. Au-, Pt-and Pd-based heterogeneous catalysts have been extensively used for the chemical oxidation of glucose to gluconic acid. Bimetallic catalysts synthesized by adding either noble or inexpensive metals have also presented excellent performance for the oxidations of glucose. In particular, particle size, which has been recognized as the most important factor that affect catalytic performances, could be rationally tuned by changing the types of support and ligand as well as the synthesis conditions. In this perspective review, we summarize and critically discuss the recent advances in the structural design of mono-and bimetallic catalysts for the oxidation of glucose in aqueous media. Furthermore, the challenges of developing catalysts for the green synthesis of gluconic acid have been highlighted. This review provides alternative insights for designing effective catalytic materials for the catalytic oxidation of bio-derived oxygenates over heterogeneous catalysts.

Stability and activity of carbon nanofiber-supported catalysts in the aqueous phase reforming of ethylene glycol

Nickel, cobalt, copper and platinum nanoparticles supported on carbon nano-fibers were evaluated with respect to their stability, catalytic activity and selectivity in the aqueous phase reforming of ethylene glycol （230 ℃, autogenous pressure, batch reactor）. The initial surface-specific activities for ethylene glycol reforming were in a similar range but decreased in the order of Pt （15.5 h-1 ） 〉Co（13.0 h 1 ） 〉Ni（5.2 h-1） while the Cu catalyst only showed low dehydrogenation activity. The hydrogen molar selectivity decreased in the order of Pt （53%）〉Co（21%）〉Ni （15%） as a result of the production of methane over the latter two catalysts. Over the Co catalyst acids were formed in the liquid phase while alcohols were formed over Ni and Pt. Due to the low pH of the reaction mixture, especially in the case of Co （as a result of the formed acids）, significant cobalt leaching occurs which resulted in a rapid deactivation of this catalyst. Investigations of the spent catalysts with various techniques showed that metal particle growth is responsible for the deactivation of the Pt and Ni catalysts. In addition, coking might also contribute to the deactivation of the Ni catalyst.

Catalytic methanation reaction over alumina supported cobalt oxide doped noble metal oxides for the purification of simulated natural gas

A series of alumina supported cobalt oxide based catalysts doped with noble metals such as ruthenium and platinum were prepared by wet impregnation method.The variables studied were difference ratio and calcination temperatures.Pt/Co(10∶90)/Al2O3 catalyst calcined at 700 ℃ was found to be the best catalyst which able to convert 70.10% of CO2 into methane with 47% of CH4 formation at maximum temperature studied of 400 ℃.X-ray diffraction analysis showed that this catalyst possessed the active site Co3O4 in face-centered cubic and PtO2 in the orthorhombic phase with Al2O3 existed in the cubic phase.According to the FESEM micrographs,both fresh and spent Pt/Co(10∶90)/Al2O3 catalysts displayed small particle size with undefined shape.Nitrogen Adsorption analysis showed that 5.50% reduction of the total surface area for the spent Pt/Co(10∶90)/Al2O3 catalyst.Meanwhile,Energy Dispersive X-ray analysis(EDX) indicated that Co and Pt were reduced by 0.74% and 0.14% respectively on the spent Pt/Co(10∶90)/Al2O3catalyst.Characterization using FT-IR and TGA-DTA analysis revealed the existence of residual nitrate and hydroxyl compounds on the Pt/Co(10∶90)/Al2O3 catalyst.

Effects of CuO-CeO₂Addition on Structure and Catalytic Properties of Three Way Catalysts

The noble metals (Pt, Pd, Rh) supported on Cu-Ce mixed oxides with γ-Al2O3 washcoat/FeCrAl substrate were investigated as catalytic performance of Three Way Catalysts (TWC) under simulated automotive exhaust feed gas. The structural, morphological features and catalytic activity were observed by X-ray diffractometry (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS) and GC-TCD (Varian CP-4900). The catalytic performance of noble metals (Pt, Rh, Pd) supported on Cu-Ce mixed oxides with γ-Al2O3 washcoat/FeCrAl substrate was be compared with noble metals (Pt, Rh, Pd) supported on Ce-Zr mixed oxides with γ-Al2O3 washcoat/FeCrAl substrate and only γ-Al2O3 washcoat/FeCrAl substrate at various stoichiometric ratio of oxygen. The results showed that the addition of Cu-Ce mixed oxides improved CO oxidation reaction at lower temperature during stable lambda of 1, the highest CO conversion of 99% is observed for the noble metals (Pt, Pd, Rh) support on Cu-Ce with γ-Al2O3 washcoat/FeCrAl substrate. The results also showed that, the addition of Cu-Ce mixed oxides promoted released oxygen, thus it improved strongly CO and C3H8 conversion at lean oxygen stoichiometric operation.