Well-ordered layered LiNi0.8Co0.1Mn0.1O2 submicron sphere with fast electrochemical kinetics for cathodic lithium storage

Nickel-rich layered oxides have drawn sustainable attentions for lithium ion batteries owing to their higher theoretical capacities and lower cost.However,nickel-rich layered oxides also have exposed several defects for commercial application,such as uncontrollable ordered layered structure,which leads to higher energy barrier for Li+diffusion.In addition,suffering from structural mutability,the bulk nickelrich cathode materials likely trigger overall volumetric variation and intergranular cracks,thus obstructing the lithium ion diffusion path and shortening the service life of the whole device.Herein,we report wellordered layered Li Ni0.8Co0.1Mn0.1O2 submicron spheroidal particles via an optimized co-precipitation and investigated as LIBs cathodes for high-performance lithium storage.The as-fabricated Li Ni0.8Co0.1Mn0.1O2 delivers high initial capacity of 228 mAh g–1,remarkable energy density of 866 Wh kg–1,rapid Li ion diffusion coefficient(10–9cm2s–1)and low voltage decay.The remarkable electrochemical performance should be ascribed to the well-ordered layered structure and uniform submicron spheroidal particles,which enhance the structural stability and ameliorate strain relaxation via reducing the parcel size and shortening Li-ion diffusion distance.This work anticipatorily provides an inspiration to better design particle morphology for structural stability and rate capability in electrochemistry energy storage devices.

Ultrafine Ni-B nanoparticles for efficient hydrogen evolution reaction

The search for active,stable,and cost-effective electrocatalysts for hydrogen evolution reaction(HER)is desirable,but it remains a great challenge in the overall water splitting.Here,we report the synthesis of nickel boron nanoparticles supported on Vulcan carbon(Ni-B)via a simple,yet scalable,two-step chemical reduction–annealing strategy.The results of the electrochemical measurements suggest that the overpotentials of Ni-B-400 are 114 and 215 mV(in 1 mol L^–1 KOH)at current densities of 10 and 40 mA cm^?2,respectively,indicating an exceedingly good electrocatalytic activity in the HER.More importantly,Ni-B maintains a current density of 7.6 mA cm^-2 at an overpotential of 0.15 V for 20 h in the durability test.The excellent HER activity of Ni-B-400 is derived from the small particle size and the expanded lattice of Ni,which can optimize the hydrogen absorption energy and enhance the electrocatalytic properties.

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.

Enhancing hydrogen electrocatalytic oxidation on Ni_(3)N/MoO_(2)in-plane heterostructures in alkaline solution

Nickel(Ni)-based materials act as one of the most promising candidates as platinum-group-metal-free(PGM-free)electrocatalysts for hydrogen oxidation reaction(HOR)in alkaline solution.Nevertheless,the electrocatalytic activity of pure Ni is significantly limited due to the sluggish kinetics under alkaline condition.To accelerate the kinetics,constructing heterostructures and nitride structures have been developed as two representative strategies.Here,we combined the two methods and presented a facile synthesis of the sheet-like Ni_(3)N/MoO_(2)in-plane heterostructures for enhanced HOR in alkaline electrolytes.Relative to Ni or Ni_(3)N,the Ni_(3)N/MoO_(2)in-plane heterostructures exhibited a significantly increased mass activity by 8.6-fold or 4.4-fold,respectively.Mechanistic studies revealed that the enhanced activity of Ni_(3)N/MoO_(2)could be attributed to the weakened hydrogen adsorption and strengthened hydroxyl adsorption.This work provides a facile approach to design high-efficiency catalysts for hydrogen-oxidation catalysis and beyond.

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.

Ordered mesoporous carbon fiber bundles with high-density and accessible Fe-NX active sites as efficient ORR catalysts for Zn-air batteries

Fe-NX/C electrocatalysts have aroused extensive interest in accelerating sluggish oxygen reduction reaction (ORR) kinetics as potential alternatives to platinum catalysts in rechargeable Zn-air batteries (ZABs).However,the low density and poor accessibility of Fe-NXsites have severely restricted the electrocatalytic performance of Fe-NX/C.Herein,Fe,N co-doped ordered mesoporous carbon fiber bundles are prepared through a ligand-assisted strategy with nitrogen-rich 1,10-phenanthroline as space isolation agent.1,10-Phenanthroline reveals a six-membered heterocyclic structure containing abundant nitrogen species to tightly coordinate with Fe ions,which is conducive to achieving high-density Fe-NXsites.Meanwhile,the adoption of SBA-15 as hard-templates enables the catalysts with highly ordered channels and large specific surface areas,improving the accessibility of Fe-NXsites.The optimal catalyst (PDA-Fe-900) demonstrates a positive half-wave potential of 0.84 V (vs.RHE) in alkaline solution,outperforming the commercial Pt/C (0.83 V).In addition,PDA-Fe-900 delivers comparable ORR performance to commercial Pt/C in acidic electrolyte.Impressively,when PDA-Fe-900 is employed as an air cathode,it achieves large power densities of 163.0 m W/cm^(2) in liquid-state ZAB and 116.6 m W/cm^(2) in the flexible solid-state ZAB.This work provides an efficient ligand-assisted pathway for fabricating catalysts with dense and accessible FeNXsites as high-performance ORR electrocatalysts for ZABs.

乙醇调控铁腐蚀构筑RuO_(x)/FeOOH电催化剂用于增强析氢性能

RuO_(x)是一种有潜力的析氢反应(HER)电催化剂,然而,其表面上*OH和*H中间体的竞争吸附以及过度H结合导致其析氢性能较差.FeOOH具有较强的亲氧性,有望与RuO_(x)耦合形成RuO_(x)/FeOOH复合材料来有效促进HER动力学.鉴于Ru^(3+)的强氧化性,构建温和的反应环境是设计结构均匀、Ru位点可及的RuO_(x)/FeOOH复合材料的关键.本文提出一种乙醇调控铁腐蚀策略,在泡沫铁上原位生长了RuO_(x)/FeOOH电催化剂.醇羟基与Ru^(3+)配位降低了Ru^(3+)的氧化性,并减缓了其扩散,避免了剧烈的氧化还原反应.优化的纳米结构以及RuO_(x)和FeOOH之间的强电子相互作用,使所制备的催化剂在50和100 mA cm^(-2)电流密度下驱动HER和全解水,分别仅需67 mV过电位和1.56 V电压.基于羟基调控策略,乙二醇、正丙醇、异丙醇和甲醇同样可替代乙醇来增强RuO_(x)/FeOOH的HER活性.本工作提出了一种调节铁腐蚀行为的配位调控方法,为制备新型钌基复合催化剂提供了理论依据.

Organic carboxylate-assisted engineering for fabricating Fe,N co-doped porous carbon interlinked carbon nanotubes towards boosting the oxygen reduction reaction for Zn-air batteries

Fe-N_x sites have been identified as core descriptors for Fe-N/C based oxygen reduction reaction catalysts.However, the low density and less utilization of Fe-Nxsites render these catalysts with inefficient catalytic performance. Herein, we develop an organic carboxylate-assisted engineering to construct Fe, N co-doped porous carbon interlinked carbon nanotubes(Fe/N-CCNTs) with high-density and sufficiently exposed FeNxsites based on self-catalyzed effect. The existing forms of Fe include Fe-imidazole configuration and coordination with unsaturated Zn sites via organic carboxylate as linkers, leading to high-density Fe-N_x sites after pyrolysis. Besides, hexatomic carbon rings of organic carboxylate lower cyclization energy barrier for CNT formation, resulting in CNTs interlinked with separated active sites through “active pointconductive line-active point” connections. The optimal sample(Fe-BOAc-PNC) exhibits the onset potential of 0.93 V(vs. RHE) and half-wave potential of 0.84 V in alkaline solution. The liquid-state Zn-air battery(ZAB) employing Fe-BOAc-PNC generates large power density(160 m W/cm^(2)) and stability over 160 h.Moreover, the assembled flexible ZAB displays superb power density of 93 m W/cm^(2) with robust flexibility. This work provides an insightful perspective for designing Fe-N/C catalysts with high-density and sufficiently exposed active sites for energy storage application.

Facile self-template fabrication of hierarchical nickel-cobalt phosphide hollow nanoflowers with enhanced hydrogen generation performance

Developing facile methods to construct hierarchical-structured transition metal phosphides is beneficial for achieving high-efficiency hydrogen evolution catalysts.Herein,a self-template strategy of hydrothermal treatment of solid Ni-Co glycerate nanospheres followed by phosphorization is delivered to synthesize hierarchical Ni Co P hollow nanoflowers with ultrathin nanosheet assembly.The microstructure of Ni Co P can be availably tailored by adjusting the hydrothermal treatment temperature through affecting the hydrolysis process of Ni-Co glycerate nanospheres and the occurred Kirkendall effect.Benefitting from the promoted exposure of active sites and affluent mass diffusion routes,the HER performance of the Ni Co P hollow nanoflowers has been obviously enhanced in contrast with the solid Ni Co P nanospheres.The fabricated Ni Co P hollow nanoflowers yield the current density of 10 m A cmà2at small overpotentials of 95 and 127 m V in 0.5 mol Là1H2SO4and 1.0 mol Là1KOH solution,respectively.Moreover,the two-electrode alkaline cell assembled with the Ni Co P and Ir/C catalysts exhibits sustainable stability for overall water splitting.The work provides a simple but efficient method to regulate the microstructure of transition metal phosphides,which is helpful for achieving high-performance hydrogen evolution catalysts based on solid-state metal alkoxides.

Self-catalyzed growth of Zn/Co-N-C carbon nanotubes derived from metal-organic frameworks as efficient oxygen reduction catalysts for Zn-air battery

Designing cost-effective and high-performance carbon-based oxygen reduction reaction(ORR)electrocatalysts is crucial in the development of Zn-air batteries(ZABs).In this study,a facile one-pot synthesis approach is engineered to construct Zn/Co-N-C carbonaceous polyhedrons interconnected with self-catalyzed-grown carbon nanotubes(CNTs)from zeolitic imidazolium frameworks linked with graphene oxide nanosheets.The special N-doped threedimensional(3 D)carbon matrix allows manipulating the exposure of active sites and the synergistic interaction between metal nanoparticles and CNTs.The as-synthesized catalyst features impressive ORR activity in 0.1 mol L^(-1)KOH(E_(1/2)=0.83 V)and 0.5 mol L^(-1)H_(2)SO_(4)(E_(1/2)=0.73 V),satisfactory cycling stability and methanol resistance comparable to those of the benchmark Pt/C catalyst(E_(1/2)=0.80 V in 0.1 mol L^(-1)KOH,E_(1/2)=0.75 V in 0.5 mol L^(-1)H_(2)SO_(4)).Furthermore,the asestablished ZAB demonstrates a competitive peak power density(90 mW cm^(-2))and prominent long-term stability,which are better than those of devices based on the commercial Pt/C catalyst(82 mW cm^(-2)).This work provides promising guidance for fabricating highly effective ORR catalysts with in situ formed CNTs,which can be applied in portable ZABrelated devices.

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.

Self-sacrificial template synthesis of Fe, N co-doped porous carbon as efficient oxygen reduction electrocatalysts towards Zn-air battery application

Designing highly efficient non-precious based electrocatalysts for oxygen reduction reaction(ORR) is of significance for the rapid development of metal-air batteries.Herein,a hydrothermal-pyrolysis method is employed to fabricate Fe,N co-doped porous carbon materials as effective ORR electrocatalyst through adopting graphitic carbon nitride(g-C_(3)N_(4)) as both the self-sacrificial templates and N sources.The gC_(3)N_(4)provides a high concentration of unsaturated pyridine-type N to coordinate with iron to form Fe-N active sites.Through adjusting the Fe doping amounts,it is proved that appropriate Fe doping content is conducive to the construction of abundant defects and active sites of Fe-N.The as-prepared catalyst exhibits superior electrocatalytic ORR performance in alkaline media with half-wave potential(E_(1/2)=0.82 V) and onset potential(E_(onset)=0.95 V),equivalent to the commercial Pt/C catalyst.Moreover,there is almost no activity loss after 10 k continuous cyclic voltammetry cycles and methanol tolerance,indicating the excellent durability and superior methanol tolerance.Remarkably,when assembled as the cathode in a Zn-air battery,the device displays a power density of 99 mW/cm^(2),an open-circuit potential of 1.48 V and long-term discharge-charge cycling stability,indicating the promising potential to substitute the Pt catalyst for practical application.