Element doping induced microstructural engineering enhancing the lithium storage performance of high-nickel layered cathodes

The high-nickel layered cathodes Li[Ni_(x)Co_(y)Mn_(1-x-y)]O_(2)(x≥0.8)with high specific capacity and long cycle life are considered as prospective cathodes for lithium-ion batteries.However,the microcrack formation and poor structural stability give rise to inferior rate performance and undesirable cycling life.Herein,we propose a dual modification strategy combining primary particle structure design and element doping to modify Li[Ni_(0.95)Co_(0.025)Mn_(0.025)]O_(2) cathode by tungsten and fluorine co-doped(W-F-NCM95).The doping of W can convert the microstructure of primary particles to the unique rod-like shape,which is beneficial to enhance the reversibility of phase transition and alleviate the generation of microcracks.F doping is conducive to alleviating the surface side reactions.Thus,due to the synergistic effect of W,F codoping,the obtained W-F-NCM95 cathodes deliver a high initial capacity of 236.1 mA h g^(-1) at 0.1 C and superior capacity retention of 88.7%over 100 cycles at 0.5 C.Moreover,the capacity still maintains73.8%after 500 cycles at 0.5 C and the texture of primary particle is intact.This work provides an available strategy by W and F co-doping to enhance the electrochemistry performance of high-nickel cathodes for practical application.

Glucose-derived carbon sphere supported CoP as efficient and stable electrocatalysts for hydrogen evolution reaction

Glucose-derived carbon sphere supported cobalt phosphide nanoparticles（Co P/C） were synthesized via a concise two-step method. The electrochemical measurement results indicate that the Co P/C prepared at 900 ℃ presents excellent electrocatalytic performance for hydrogen evolution reaction（HER）. The overpotential at a current density of 10 m A cmis 108 and 163 mV in 0.5 M HSOand 1 M KOH, respectively, and maintains its electrocatalytic durability for at least 10 h. This work supplies a new field to challenge the construction of electrocatalysts for HER through using cost-effective carbon supported transition metal phosphides.

Insight into the hydrogen oxidation electrocatalytic performance enhancement on Ni via oxophilic regulation of MoO_(2)

Exploring platinum-group-metal(PGM)free electrocatalysts for hydrogen oxidation reaction(HOR)in alkaline media is essential to the progress of anion exchange membrane fuel cells(AEMFCs).In this work,a Ni/MoO_(2) heterostructure catalyst with comparable HOR activity in alkaline electrolyte with PGM catalyst was prepared by a simple hydrothermal-reduction method.Remarkably,the Ni/MoO_(2) presents a mass kinetic current density of 38.5 mA mgNi^(-1) at the overpotential of 50 mV,which is higher than that of the best PGM free HOR catalyst reported by far.Moreover,the HOR performance of Ni/MoO_(2) under 100 ppm CO shows negligible fading,together with the superior durability,render it significant potential for application in AEMFCs.A particular mechanistic study indicates that the excellent HOR performance is ascribed to the accelerated Volmer step by the incorporation of MoO_(2).The function of MoO_(2) was further confirmed by CO striping experiment on Pt/C-MoO_(2) that MoO_(2) can facilitated OH adsorption thus accelerate the HOR process.On account of the high performance and low cost,the Ni/MoO_(2) electrocatalyst encourages the establishment of high performance PGM free catalyst and shows significant potential for application in AEMFCs.

Advances of Synergistic Electrocatalysis Between Single Atoms and Nanoparticles/Clusters

Combining single atoms with clusters or nanoparticles is an emerging tactic to design efficient electrocatalysts.Both synergy effect and high atomic utilization of active sites in the composite catalysts result in enhanced electrocatalytic performance,simultaneously provide a radical analysis of the interrelationship between structure and activity.In this review,the recent advances of single-atomic site catalysts coupled with clusters or nanoparticles are emphasized.Firstly,the synthetic strategies,characterization,dynamics and types of single atoms coupled with clusters/nanoparticles are introduced,and then the key factors controlling the structure of the composite catalysts are discussed.Next,several clean energy catalytic reactions performed over the synergistic composite catalysts are illustrated.Eventually,the encountering challenges and recommendations for the future advancement of synergistic structure in energy-transformation electrocatalysis are outlined.

Self-templating construction of hollow microspheres assembled by nanosheets with exposed active planes for sodium ion storage

P2-type layered metal oxides have been considered as one of the promising cathode candidates for high-performance Na-ion batteries(SIBs).However,it is still challenging to balance the contradiction of high energy density and long cycle life due to the structural degradation and sluggish ion diffusion dynamics.Here,the hierarchical P2-Na2/3Ni1/3Mn2/3O2 hollow microspheres assembled by nanosheets are constructed via a self-template approach.The obtained nanosheets with more exposed electrochemical active planes serving as desodiation/sodiation reactors can provide substantial Na+channels,shorten the diffusion pathways,and accommodate the volume changes during charge/discharge process.Benefiting from the facile Na+diffusion paths and optimal architecture modulation,the cathode delivers a high initial Coulombic efficiency of 96.0%with a high energy density of 299.7 Wh·kg^(−1).The highly reversible structural evolutions processes are verified by galvanostatic intermittent titration technique(GITT)and operando electrochemical impedance spectroscopy(EIS)measurement,which would significantly improve the cycle stability(83.3%capacity retention at 1.0 C over 500 loops).Furthermore,the full cell assembled by hard carbon presents a high reversible capacity of 71 mAh·g^(−1)at 0.2 C and promising capacity retention(91.5%after 50 cycles).The designing concept of morphological configuration in this work paves an accessible route for building high-performance electrode materials.

High-entropy L1_(2)-Pt(FeCoNiCuZn)_(3) intermetallics for ultrastable oxygen reduction reaction

Enhancing the stability of Pt-based electrocatalysts for the sluggish cathodic oxygen reduction reaction(ORR)is critical for proton exchange membrane fuel cells(PEMFCs).Herein,high-entropy intermetallic(HEI)L1_(2)-Pt(FeCoNiCuZn)3is designed for durable ORR catalysis.Benefiting from the unique HEI structure and the enhanced intermetallic phase stability,Pt(FeCoNiCuZn)3/C nanoparticles demonstrate significantly improved stability over Pt/C and PtCu_(3)/C catalysts.The Pt(FeCoNiCuZn)3/C exhibits a negligible decay of the half-wave potential during 30,000 potential cycles from 0.6 to 1.0 V,whereas Pt/C and PtCu_(3)/C are negatively shifted by 46 and 36 m V,respectively.Even after 10,000 cycles at potential up to 1.5 V,the mass activity of Pt(FeCoNiCuZn)3/C still shows~70%retention.As evidenced by the structural characterizations,the HEI structure of Pt(FeCoNiCuZn)3/C is well maintained,while PtCu_(3)/C nanoparticles undergo severe Cu leaching and particle growth.In addition,when assembled Pt(FeCoNiCuZn)3/C as the cathode in high-temperature PEMFC of 160℃,the H_(2)-O_(2)fuel cell delivers almost no degradation even after operating for 150 h,demonstrating the potential for fuel cell applications.This work provides a facile design strategy for the development of high-performance ultrastable electrocatalysts.

Rational design of three-dimensional nitrogen and phosphorus co-doped graphene nanoribbons/CNTs composite for the oxygen reduction

In the present work, we report nitrogen and phosphorus co-doped 3-D structured carbon nanotube intercalated graphene nanoribbon composite. The graphene nanoribbons are prepared via partial exfoliation of multi-walled carbon nanotubes. In the graphene nanoribbons/CNTs composite, carbon nanotubes play a role of skeleton and support the exfoliated graphene nanoribbons to form the stereo structure. After high temperature heat-treatment with ammonium dihydrogen phosphate, the unique structure reserves both the properties of carbon nanotube and graphene, exhibiting excellent catalytic performance for the ORR with excellent onset and half-wave potential, which is similar to commercial Pt/C electrocatalysts.

Engineering titanium oxide-based support for electrocatalysis

The corrosion and weaker interaction with metal catalysts of common carbon supports during electrocatalysis push the development of alternative supports materials. Titanium oxide-based materials have been widely explored as electrocatalysts supports in consideration of their chemical stability, strong interactions with metal catalyst and wider applications in electrocatalytic reactions as well as the improved electronic conductivity. This review summarizes recent research advances in engineering titanium oxide-based supports for the catalysts in electrocatalysis field to provide guidance for designing high performance non-carbon supported electrocatalysts. Typically, the titanium oxide-based supports are classified into shaped TiO_(2), doped TiO_(2), titanium suboxide and TiO_(2)-carbon composites according to the modification methods and corresponding preparation methods. Then the engineering strategies and electrocatalytic applications are discussed in detail. Finally, the challenges, future research directions and perspectives of titanium oxide-based supports for electrocatalysis are presented for practical applications.

A review on the forward osmosis applications and fouling control strategies for wastewater treatment

During the last decades,the utilization of osmotic pressure-driven forward osmosis technology for wastewater treatment has drawn great interest,due to its high separation efficiency,low membrane fouling propensity,high water recovery and relatively low energy consumption.This review paper summarizes the implementation of forward osmosis technology for various wastewater treatment including municipal sewage,landfill leachate,oil/gas exploitation wastewater,textile wastewater,mine wastewater,and radioactive wastewater.However,membrane fouling is still a critical issue,which affects water flux stability,membrane life and operating cost.Different membrane fouling types and corresponding fouling mechanisms,including organic fouling,inorganic fouling,biofouling and combined fouling are therefore further discussed.The fouling control strategies including feed pre-treatment,operation condition optimization,membrane selection and modification,membrane cleaning and tailoring the chemistry of draw solution are also reviewed comprehensively.At the end of paper,some recommendations are proposed.

Investigation of MXenes as oxygen reduction electrocatalyst for selective H_(2)O_(2) generation

Two-electron oxygen reduction reaction(ORR)catalysts are essential for the electrosynthesis of hydrogen peroxide(H_(2)O_(2)).MXenes,a rising family of two-dimensional(2D)transition metal carbides,have been extensively studied for energy storage and(photo)electrocatalysis due to their rich chemical compositions and tunable electronic structures.In this work,three representative MXenes of Ti_(3)C_(2)T_(x),V_(2)CTX,and Nb_(2)CTX were selected for H_(2)O_(2)electrosynthesis and we found that MXenes are inherent two-electron ORR catalysts with high H_(2)O_(2)selectivity.In addition,this work critically evaluates their electrocatalytic activity and stability.Interestingly,Nb_(2)CT_(x)catalyst maintains better electrocatalytic activity and higher stability for a long time test,although the stability of Ti_(3)C_(2)T_(x)and V_(2)CT_(x)catalysts is poor owing to the metal dissolution property of Ti and V in alkaline media.Moreover,the assembled device based on Nb2CTx catalyst presents a high H2O2 production and a rapid organic dye decoloration ability.

Molybdenum-doped titanium dioxide supported low-Pt electrocatalyst for highly efficient and stable hydrogen evolution reaction

The Platinum(Pt)-based catalysts exhibit excellent catalytic performance for the hydrogen evolution reaction(HER) while suffering from poor stability due to the weak interaction between the carbon support and Pt.Herein,a molybdenum-doped titanium dioxide(Ti_(0.9)Mo_(0.1)O_(2)) supported low-Pt electrocatalyst with stronger interaction between catalyst and support is applied to tune the electrocatalytic performance of Pt.The Ti_(0.9)Mo_(0.1)O_(2) support can not only tolerate the corrosion environment in the catalytic system,but also generate strong metal-support inte raction(SMSI) between the oxide and catalyst.A facile solvothermal method is used to prepareTi_(0.9)Mo_(0.1)O_(2) as support to anchor Pt nanoparticles.The 5% Pt supported on Ti_(0.9)Mo_(0.1)O_(2) catalyst exhibits 4.4-fold mass activity(MA) at an overpotential of 50 mV and higher stability than 20% Pt/C with only 1/4 Pt loading.The SMSI between the Ti_(0.9)Mo_(0.1)O_(2) and Pt prevents the Pt aggregation to achieve excellent stability,and hydrogen spillover effect in the interface between Pt and support benefits the hydrogen production process.This work presents a novel sight for the fabrication and design of oxide supported catalysts in various catalytic system by reasonably employing support effect.

Boosting alkaline hydrogen electrooxidation on an unconventional fcc-Ru polycrystal

Precisely controlling the crystalline phase structure and exposed facets at the atomic level opens up a new avenue for efficient catalyst design.Along this line,we report an unconventional face-centered cubic(fcc)Ru with twinned structure and stacking-fault defects as a competent electrocatalyst towards alkaline hydrogen oxidation reaction(HOR),which is now a major obstacle for the commercialization of anion exchange membrane fuel cells(AEMFC).With conventional hexagonal close packing(hcp)Ru as the counterpart,a novel scope from the phase-engineering is introduced to identify the activity origin and provide fundamental understanding of the sluggish HOR kinetics in alkaline medium.Systematic electrochemical analysis assisted by deconvoluting the hydrogen(H)desorption peaks indicates the superior performance of fcc Ru origins from the structure defects and higher proportion of the most active sites.DFT calculations,together with CO-stripping voltammograns further corroborate the stronger hydroxyl species(OH^(*))affinity lead to the higher activity on these sites.Meanwhile,it also demonstrates the H^(*)adsorption/desorption on polycrystalline Ru among the conventional"hydrogen region"is accompanied by the surface bound OH^(*)in alkaline medium,which is of great significance for subsequent alkaline HOR exploration and catalyst design.

Biomass derived nitrogen doped carbon with porous architecture as efficient electrode materials for supercapacitors

Developing porous carbon materials with low-cost, sustainable and eco-friendly natural resources is emerging as an ever important research field in the application of high-performance supercapacitor. In this paper, a simple synthetic method to fabricate nitrogen doped porous carbon （NPC） is developed via a one-pot carbonization of sodium alginate and urea. The as-prepared NPC annealed at 700℃ with meso- and macro-porous structure exhibits excellent specific capacitance （180.2 F/g at 1 A/g） and superior cycling life when serves as electrode materials for supercapacitor. Moreover, the investigation on the annealing temperature demonstrates that NPC pyrolysis at 700℃ possesses relatively high pyrrole nitrogen and pyridine nitrogen, which is favorable for enhancing supercapacitor performance. This work extends biomass derived carbon materials in energy storage applications.

Highly active N-doped carbon encapsulated Pd-Fe intermetallic nanoparticles for the oxygen reduction reaction

Developing highly efficient non-R catalysts for fuel cells and metal-air batteries is highly desirable but still challenging due to the sluggish oxygen reduction reaction(ORR).Herein,a facile and efficient strategy is demonstrated to prepare N-doped carbon encapsulated ordered Pd-Fe intermetallic(O-Pd-Fe@NC/C)nanoparticles via a one-step thermal annealing method.The obtained O-Pd-Fe@NC/C nanoparticles show enhanced ORR activity,durability and anti-poisoning capacity in both acid and alkaline medium.When O-Pd-Fe@NC/C serving as cathode catalyst for Zn-air battery,it exhibits higher voltage platform and superior cycling performance with respect to the Zn-air battery based on the mixture of Pt/C and Ir/C catalysts.The enhanced electrocatalytic performance can be ascribed to the formation of face-centered tetragonal(fct)Pd-Fe nanoparticles,the protective action of the N-doped carbon layer and the interface confinement effect between them.The in situ formed N-doped carbon shell not only restrains the Pd-Fe ordered intermetallics from aggregating effectively during the thermal annealing process,but also provides a strong anchoring effect to avoid the detachment of Pd-Fe nanoparticles from the carbon support during the potential cycling.This facile carbon encapsulation strategy may also be extended to the preparation of a wide variety of N-doped carbon encapsulated intermetallic compounds for fuel cell application.

Ultrafine molybdenum carbide nanoparticles supported on nitrogen doped carbon nanosheets for hydrogen evolution reaction

Molybdenum carbides(Mo_xC)/nitrogen doped carbon nanosheets(NCS) composites are synthesized via simple mixing melamine and ammonia molybdate, followed by a high-temperature treatment. Metal carbide nanoparticles with ultra-small size(13nm) are uniformly supported on nitrogen doped carbon nanosheets. The hydrogen evolution reaction(HER) is investigated in both 0.5 mol/L H_2SO_4 and 1 mol/L KOH media. Mo_2C/NCS-10(melamine/ammonia molybdate weight ratio of 10:1) exhibits excellent performance with a low overpotential of 130 mV in 0.5 mol/L H_2SO_4 solution and 108 mVin 1mol/L KOH solution at the current density of 10 mA/cm^2. The better electrocatalytic activity could be ascribed to Ndoped carbon nanosheets, small particle size, mesoporous structure, and large specific surface area,which could provide the large electrochemical active surface area and facilitate mass transport.

Semi-interpenetrating polymer networks toward sulfonated poly(ether ether ketone) membranes for high concentration direct methanol fuel cell

Low methanol permeability of proton exchange membranes (PEMs) is greatly important for direct methanol fuel cells (DMFCs). Here, sulfonated poly (ether ether ketone) (SPEEK) based semiinterpenetrating polymer networks (semi-IPNs) are successfully prepared by interpenetrating SPEEK into the in-situ synthesized crosslinking networks. The polymeric networks are formed by the covalent bonds between bromobenzyl groups of bro mo methylated poly (phenylene oxide) and amine groups of diamine linkers as well as the ionic bonds between amine species and sulfonated groups. Two linkers without and with sulfonated groups are applied to fabricate the semi-IPNs. The core properties of the membranes, like phase separation, water uptake, proton conductivity and methanol permeability, are systematically studied and compared. The DMFCs assembled by using the semi-IPN membranes display better performance than Nafion 117 in high concentration methanol solutions. The present work provides a facile way to prepare PEMs with enhanced DMFC performance.

A self-supported heterogeneous bimetallic phosphide array electrode enables efficient hydrogen evolution from saline water splitting

Hydrogen generation from water splitting is of great prospect for the sustainable energy conversion.However,it is still challenging to explore stable and high-performance electrocatalysts toward hydrogen evolution reaction(HER)from saline water such as seawater due to the chloride corrosion.Herein,we developed a self-supported heterogeneous bimetallic phosphide(Ni_(2)P-FeP)array electrode that possesses excellent HER performance in alkaline saline water with an overpotential of 89 mV at 10 mA·cm^(−2)and long-term stability over 90 h at 200 mA·cm^(−2).The analysis showed that the heterostructure between the interfaces of Ni_(2)P-FeP plays a pivotal role in promoting the activity of catalyst.Moreover,the bimetallic phosphide nanoarrays can be employed as a shield for chlorine-corrosion resistance in the saline water,ensuring the long-term durability of hydrogen generation.When employed for alkaline saline water electrolysis,a current density of 100 mA·cm^(−2)is achieved at cell voltage of 1.68 V.This work presents an effective approach for the fabrication of high-performance electrode for HER in alkaline saline environments.