Electronic Communication Between Co and Ru Sites Decorated on Nitrogen-Doped Carbon Nanotubes Boosting the Alkaline Hydrogen Evolution Reaction

Designing highly efficient Pt-free electrocatalysts with low overpotential for an alkaline hydrogen evolution reaction(HER)remains a significant challenge.Here,a novel and efficient cobalt(Co),ruthenium(Ru)bimetallic electrocatalyst composed of CoRu nanoalloy decorated on the N-doped carbon nanotubes(CoRu@N-CNTs),was prepared by reacting fullerenol with melamine via hydrothermal treatment and followed by pyrolysis.Benefiting from the electronic communication between Co and Ru sites,the as-obtained CoRu@N-CNTs catalyst exhibited superior electrocatalytic HER activity.To deliver a current density of 10 mA·cm^(-2),it required an overpotential of merely 19 mV along with a Tafel slope of 26.19 mV·dec^(-1)in 1 mol·L^(-1)potassium hydroxide(KOH)solution,outperforming the benchmark Pt/C catalyst.The present work would pave a new way towards the design and construction of an efficient electrocatalyst for energy storage and conversion.

氧气高炉条件下含铁炉料的程序还原行为实验研究

采用高炉多区域约束数学模型对典型氧气高炉流程进行模拟计算,确定了其在不同位置处的煤气成分,并结合传统高炉的升温制度,采用程序还原实验装置对含铁炉料在氧气高炉和传统高炉中的还原历程进行研究。结果表明,氧气高炉条件下,烧结矿和球团矿的还原开始温度较传统高炉分别降低60℃和150℃;当温度达到1 100℃时,氧气高炉条件下,烧结矿和球团矿的还原度(RI)基本均达到100%,而传统高炉下其还原度(1 RI)分别为94%和83.1%。另外,经对反应后炉料的化学分析得出,氧气高炉条件下烧结矿和球团矿中的含碳量分别约为传统高炉条件下的10倍和2.5倍。

Co_3O_4 supported on N,P-doped carbon as a bifunctional electrocatalyst for oxygen reduction and evolution reactions

Noble metals, such as platinum, ruthenium and iridium‐group metals, are often used as oxygen reduction or evolution reaction （ORR/OER） electrocatalysts. To reduce the cost and provide an application of bifunctional catalysis, in this work, cobalt oxide supported on nitrogen and phospho‐rus co‐doped carbon （Co3O4/NPC） was fabricated and examined as a bifunctional electrocatalyst for OER and ORR. To prepare Co3O4/NPC, NPC was pyrolyzed from melamine and phytic acid support‐ed on carbon, followed by the solvothermal synthesis of Co3O4 on NPC. Linear sweep voltammetry was used to evaluate the activity for OER and ORR. For OER, Co3O4/NPC showed an onset potential of 0.54 V （versus the saturated calomel electrode） and a current density of 21.95 mA/cm2 at 0.80 V, which was better than both Co3O4/C and NPC. The high activity of Co3O4/NPC was attributed to a synergistic effect of the N, P co‐dopants and Co3O4. For ORR, Co3O4/NPC exhibited an activity close to commercial Pt/C in terms of the diffusion limited current density （–4.49 vs–4.76 mA/cm2 at–0.80 V）, and Co3O4 played the key role for the catalysis. Chronoamperometry （current versus time） was used to evaluate the stability, which showed that Co3O4/NPC maintained 46%current after the chronoamperometry test for OER and 95% current for ORR. Overall, Co3O4/NPC exhibited high activity and improved stability for both OER and ORR.

Amorphous Ru nanoclusters onto Co‐doped 1D carbon nanocages enables efficient hydrogen evolution catalysis

The development of high-performance electrocatalysts for hydrogen evolution reaction(HER)is of great significance for green,sustainable,and renewable energy conversion.Herein,we report the synthesis of amorphous Ru clusters on Co-doped defect-rich hollow carbon nanocage(a-Ru@Co-DHC)as an efficient electrocatalyst for HER in the basic media.Due to the advantages such as high surface area,rich edge defect,atomic Co doping and amorphous Ru clusters,the as-made a-Ru@Co-DHC displays an efficient HER performance with a near-zero onset overpotential,a low Tafel slope(62 mV dec^(−1)),a low overpotential of 40 mV at 10 mA cm^(−2) and high stability,outperforming the commercial Ru nanocrystal/C,commercial Pt/C,and other reported Ru-based catalysts.This work provides a new insight into designing new metal doped carbon nanocages catalysts supported by amorphous nanoclusters for achieving the enhanced electrocatalysis.

MXenes for electrocatalysis applications:Modification and hybridization

Two-dimensional carbides,nitrides,and carbonitrides(MXenes)play important roles in promoting the development of sustainable energy because they have abundant reactive sites on their surfaces.An increasing number of MXenes with diverse elements and composites have been predicted and synthesized for electrocatalysis applications since the first report of a Ti-Mo-based MXene for the hydrogen evolution reaction(HER).Herein,we summarize the progress of MXene-based electrocatalysts for the HER,the oxygen evolution reaction,and the oxygen reduction reaction,including regulated pristine MXenes and modified hybrid MXenes,from both theoretical and experimental perspectives.A brief overview on MXene synthesis is presented first,accompanied by a discussion on the relationship between electrocatalytic properties and M,X,T,vacancies,and morphologies.After reviewing strategies in terms of atom substitution,functional modification,defect engineering,and morphology control,we emphasize the construction of heterojunctions between MXenes and other nanostructures,such as metal nanoparticles,oxides,hydroxides,sulfides,and phosphides.We finally discuss prospects for the future development of MXene-based electrocatalysts.

Robust MOF-253-derived N-doped carbon confinement of Pt single nanocrystal electrocatalysts for oxygen evolution reaction

Although carbon-supported platinum(Pt/C) is still considered the most active electrocatalyst for hydrogen evolution reaction(HER) and oxygen reduction reaction(ORR), its applications in metal–air batteries as a cathode catalyst, or for oxygen generation via water splitting electrolysis as an anode catalyst is mainly constrained by the insufficient kinetic activity and stability in the oxygen evolution reaction(OER). Here, MOF-253-derived nitrogen-doped carbon(N/C)-confined Pt single nanocrystals(Pt@N/C) have been synthesized and shown to be efficient catalysts for the OER. Even with low Pt mass loading of 6.1 wt%(Pt@N/C-10), the catalyst exhibits greatly improved activity and long-time stability as an efficient OER catalyst. Such high catalytic performance is attributed to the core-shell structure relationship, in which the active N-doped-C shell not only provides a protective shield to avoid rapid Pt nanocrystal oxidation at high potentials and inhibits the Pt migration and agglomeration, but also improves the conductivity and charge transfer kinetics.

CoNiP/NC polyhedrons derived from cobalt-based zeolitic imidazolate frameworks as an active electrocatalyst for oxygen evolution

The oxygen evolution reaction(OER)plays an important role in the development of energy conversation and storage technologies including water splitting and metal-air batteries,where the development of electrocatalysts is paramount.In this study,cobalt-nickel phosphide/N-doped porous carbon polyhedron electrocatalysts(CoNiP/NC)were prepared by a facile two-step carbonization method and subsequent phosphorization calcination in an Ar atmosphere using cobalt-based zeolitic imidazolate frameworks(ZIFs)as precursors.Among the electrocatalysts obtained by controlling the carbonization and phosphorization temperature,the CoNiP/NC700 catalyst,where 700 refers to the calcination temperature(°C),exhibited superior electrocatalytic activity for the OER with an onset overpotential of approximate 220 mV and an overpotential of approximate 300 mV in alkaline solution at a current density of 10 mA/cm2.The CoNi/NC and Co/NC Samples were also tested for comparison and CoNiP/NC exhibited the better electrocatalytic activity at all the temperatures tested.The superior electrocatalytic activity of the phosphorization hybrid material can be attributed to the superior synergistic effect of Co,Ni,P and C due to their strong electron coupling interactions.The interconnected amorphous carbon anchored the active Co compounds to avoid aggregation and maintained conducting channels for electron transfer.The composite electrocatalyst prepared herein is a promising candidate for use in electrocatalytic OERs.

Effects of Cu content on microstructures and compressive mechanical properties of CNTs/Al-Cu composites

The carbon nanotubes(CNTs) reinforced Al-Cu matrix composites were prepared by hot pressing sintering and hot rolling, and the effects of Cu content on the interfacial reaction between Al and CNTs, the precipitation behavior of Cu-containing precipitates, and the resultant mechanical properties of the composites were systematically investigated. The results showed that the increase of Cu content can not only increase the number and size of Cu-containing precipitate generated during the composite fabrication processes, but also promote the interfacial reaction between CNTs and Al matrix, leading to the intensified conversion of CNTs into Al_(4)C_(3). As a result, the composite containing 1 wt.% Cu possesses the highest strength, elastic modulus and hardness among all composites, due to the maintenance of the original structure of CNTs. Moreover, the increase of Cu content can change the dominant strengthening mechanisms for the enhanced strength of the fabricated composites.

Synergistic effect of metallic nickel and cobalt oxides with nitrogen-doped carbon nanospheres for highly efficient oxygen evolution

The most energy-inefficient step in the oxygen evolution reaction(OER), which involves a complicated four-electron transfer process, limits the efficiency of the electrochemical water splitting. Here, well-defined Ni/Co3O4 nanoparticles coupled with N-doped carbon hybrids(Ni/Co3O4@NC) were synthesized via a facile impregnation-calcination method as efficient electrocatalysts for OER in alkaline media. Notably, the impregnation of the polymer with Ni and Co ions in the first step ensured the homogeneous distribution of metals, thus guaranteeing the subsequent in situ calcination reaction, which produced well-dispersed Ni and Co3O4 nanoparticles. Moreover, the N-doped carbon matrix formed at high temperatures could effectively prevent the aggregation and coalescence, and regulate the electronic configuration of active species. Benefiting from the synergistic effect between the Ni, Co3O4, and NC species, the obtained Ni/Co3O4@NC hybrids exhibited enhanced OER activities and remarkable stability in an alkaline solution with a smaller overpotential of 350 m V to afford 10 m A cm-2, lower Tafel slope of 52.27 m V dec-1, smaller charge-transfer resistance, and higher double-layer capacitance of 25.53 m F cm-2 compared to those of unary Co3O4@NC or Ni@NC metal hybrids. Therefore, this paper presents a facile strategy for designing other heteroatom-doped oxides coupled with ideal carbon materials as electrocatalysts for the OER.

Hierarchical CoSeS nanostructures assisted by Nb doping for enhanced hydrogen evolution reaction

Metal doping for active sites exhibits remarkable potential for improving the hydrogen evolution reaction(HER).Multi-doping and the use of a conductive substrate can further modulate catalytic performance.Herein,Nb-CoSe well dispersed in N-doped carbon nanospheres(NCs,Nb-CoSe@NC)was synthesized to serve as a conductive substrate and facilitated good dispersion of active sites for the HER.Nb doping can also change the electronic structure of CoSe,which facilitates the activity for the HER.In order to further improve the conductivity and intrinsic activity of Nb-CoSe@NC,dual,nonmetal doping was realized through gas sulfurization to prepare hierarchical Nb-CoSeS@NC.The prepared Nb-CoSeS@NC,with a core-shell structure,exhibited a low overpotential of 115 mV at 10 mA cm–2,which is smaller than that of the most doped catalysts.In addition,NCs not only improved the dispersion and conductivity of the catalyst but also prevented metal corrosion in an electrolyte,thus facilitating the long-term stability of Nb-CoSeS@NC.Moreover,the synergistic effect of the multi-doping of Nb,S,and Se was explained.This work provides a promising,multi-doping strategy for the large-scale application of transition-metal-based electrocatalysts for the HER.

Controlling atomic phosphorous-mounting surfaces of ultrafine W_(2)C nanoislands monodispersed on the carbon frameworks for enhanced hydrogen evolution

Controllably mounting foreign atoms on the surfaces of earth-abundant electrocatalysts strongly improve their surface electronic properties for optimizing the catalytic performance of surficial sites to an unusual level,and provides a good platform to gain deep insights into catalytic reactions.The present work describes,employing ultrafine W2C nanoislands(average size:2.3 nm)monodispersed on the N,P dual-doped carbon frameworks as a model system,how to regulate the atomic phosphorous-mounting effect on the surfaces of W_(2)C to derive an active and stable P-mounting W_(2)C(WCP)catalyst for both acidic and alkaline hydrogen evolution reaction(HER).Since in situ phosphorus substitution into carbon sites of preformed W_(2)C nanoislands gradually proceeds from surfaces to solids,so that using a proper amount of phosphorus sources can readily control the surface mounting level to avoid the mass P-doping into the bulk.By this way,the activity per active site of WCP catalyst with robust stability can be optimized to 0.07 and 0.56 H_(2 )s^(-1) at-200 mV overpotential in acid and base,respectively,which reach up to the several-fold of pure-phase W_(2)C(0.01 and 0.05 H_(2) s^(-1)).Theoretical investigations suggest that compared with solid P doping,the P mounting on W_(2)C surface can more remarkably enhance its metallicity and decrease the hydrogen release barrier.This finding disclosed a key correlation between surface foreign atom-mounting and catalytic activity,and suggested a logical extension to other earth-abundant catalysts for various catalytic reactions.

Effects of Formulation Parameters and Process Variables on the Properties of Granules Obtained by Reactive Granulation

In this work, granulation between dodecyl-benzenesulfonic acid and sodium carbonate was investigated in a laboratory-scale high shear mixer. The effects offormulation parameters and process variables, including primary carbonate size, binder content, impeller speed, and operating temperature, were correlated to the properties ofthe product granules. Design ofexperiment and analysis ofvariance were combined to analyze the experimentaldata, and results showed that larger granule sizes with fewer fine particles can be obtained by employing higher binder contents and larger sodium carbonate sizes. The shear force ofthe impeller can extensively break oversized granules. The binder content exerted a contrasting effect on the flowability ofgranules formed with two kinds ofsodium carbonate, likely because ofdifferences in the liquid saturation ofthe solids. The dissolution rate determined by in-line size analysis showed that high binder contents were beneficialto dissolution performance, and the relationships between Hunter color and tested parameters were evaluated. The results ofthis work can be used as a reliable guidance for process controland optimization in powder detergent manufacturing.

N‐doped porous carbon nanofibers inlaid with hollow Co_(3)O_(4) nanoparticles as an efficient bifunctional catalyst for rechargeable Li‐O_(2) batteries

Stable and high‐efficiency bifunctional catalysts for the oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)are desired for the practical application of Li‐O_(2)batteries with excellent rate performance and cycle stability.Herein,a novel hybrid bifunctional catalyst with carbon nanofibers inlaid with hollow Co_(3)O_(4)nanoparticles and separate active sites for ORR and OER were prepared and applied in Li‐O_(2)batteries.Benefiting from the synergistic effect of unique porous structural features and high electrocatalytic activity of hollow Co3O4 intimately bound to N‐doped carbon nanofibers,the assembled Li‐O_(2)batteries with novel catalyst exhibited high specific capacity,excellent rate capability,and cycle stability up to 150 cycles under a capacity limitation of 500 mAh g^(–1)at a current density of 100 mA g^(–1).The facile synthesis and preliminary results in this work show the as‐prepared catalyst as a promising bifunctional electrocatalyst for applications in metal‐air batteries,fuel cells,and electrocatalysis.

Multiple carbon interface engineering to boost oxygen evolution of Ni Fe nanocomposite electrocatalyst

Interface engineering has been widely investigated to regulate the structure and performance of electrodes and photoelectrodes,but the investigation of multiple carbon interface modifications on the electrocatalytic oxygen evolution reaction(OER)is still shortage.Herein,we report remarkable promotion of OER performance on the NiFe‐based nanocomposite electrocatalyst via the synergy of multiple carbon‐based interface engineering.Specifically,carbon nanotubes were in situ grown on carbon fiber paper to improve the interface between CFP and NiFeO_(x)H_(y),and graphite carbon nanoparticles were in situ loaded and partly doped into the NiFeO_(x)H_(y) to modify the intergranular interface charge transfer and electronic structure of NiFeO_(x)H_(y).Consequently,the as‐obtained NiFeO_(x)H_(y)‐C/CNTs/CFP catalyst exhibited significantly enhanced electrocatalytic OER activity with an overpotential of 202 mV at 10 mA cm^(-2) in 1 mol L^(-1) KOH.Our work not only extends application of carbon materials but also provides an alternative strategy to develop highly efficient electrocatalysts.

Fabrication of multifunctional carbon encapsulated Ni@NiO nanocomposites for oxygen reduction,oxygen evolution and lithium-ion battery anode materials

Multifunctional carbon encapsulated Ni@NiO nanocomposites（Ni@NiO@C） were synthesized for applications in oxygen reduction reactions（ORR）,oxygen evolution reactions（OER） and lithium-ion batteries（LIB）. The morphology was investigated via SEM and TEM,suggesting that the Ni@NiO@C nanocomposites have uniform and spherical core-shell structures. When the Ni@NiO@C nanocomposite is used as the catalyst in ORR,90% of the initial current density can be maintained after 15h in O_2-saturated 0.1 mol L^-1 KOH at 0.3 V under a rotation speed of 1600rpm.As a catalyst for OER,the highest activity overpotential of the Ni@NiO@C nanocomposite electrocatalyst is 380 mV（vs.RHE） under the current density of 10 mA cm^（-2）,and the Tafel slope was calculated to be 55 mV dec^-1 by linear fitting. Electrochemical performances of the Ni@NiO@C nanocomposites used as LIB electrodes exhibited a long cycling life with a high capacity of 750 mA h g^-1 after 400 cycles under 200 mA g^-1.

Carbon skeleton doped with Co, N, S and P as efficient electrocatalyst for oxygen evolution reaction

A new strategy for the preparation of highly efficient catalyst used in oxygen evolution reaction （OER） in alkaline media was developed. A Co-containing carbonitride polymer network （CoCN） was selected as a structural-direct- ing template and a hypercross-linked polymer containing S and P, which formed on CoCN skeleton in situ, was used as a cover. After calcination at 450℃ for 2 h, an interconnected nanostructure was obtained and showed excellent activity and high stability for electrochemical water splitting. Trace amount of Co and other heteroatoms including N, S, P and the formed Co-N and Co-O species are essential for the im- pressive catalysis performance. The calcination temperature of 450℃ is optimal to the catalysis performance. These results suggest that Co in addition to heteroatom-doped （S, P） car- bonitride could be used as a supplement and/or an alternative to noble metal oxides for water splitting.

Facile synthesis and excellent electrochemical performance of CoP nanowire on carbon cloth as bifunctional electrode for hydrogen evolution reaction and supercapacitor

In this paper, we report CoP nanowires supported on carbon cloth （CC） （CoP/CC） as a bifunctional electrode for hydrogen evolution reaction （HER） and supercapacitor. CoP/CC possess an excellent electrocatalytic performance for HER, with a Tafel slope of 56 mV/dec and a low overpotential of 68 mV to achieve a current density of 10 mAcm^-2. Remarkably, the bifunctional CoP/CC used as electrode for supercapacitor exhibit a higher specific capacitance of 674 F g^-1 at a scan rate of 5 mV s^-1 and maintains long-life cycling stability, retaining 86% of the initial capacitance after 10,000 cycles. CoP/CC will be a promising candidate as electrode for HER and supercapacitor.

Holey platinum nanotubes for ethanol electrochemical reforming in aqueous solution

The catalytic/electrocatalytic performance of platinum(Pt)nanostructures highly relates to their morphology.Herein,we propose a facile self-template pyrolysis strategy at high temperature to synthesize one-dimensionally holey Pt nanotubes(Pt-hNTs)using Pt^(Ⅱ)-dimethylglyoxime complex(Pt^(Ⅱ)-DMG)nanorods as the reaction precursor.The coordination capability of DMG results in the generation of Pt^(Ⅱ)-DMG nanorods,whereas the reducibility of DMG at high temperature leads to the reduction of Pt^(Ⅱ)species in Pt^(Ⅱ)-DMG nanorods.During the reaction process,the inside-out Ostwald ripening phenomenon leads to the hollow morphology of Pt-hNTs.Benefiting from the physical characteristics of hollow and holey structure,Pt-hNTs with clean surface show superior electroactivity and durability for catalyzing ethanol electrooxidation as well as hydrogen evolution reaction in alkaline media.Under optimized experimental conditions,the constructed symmetric Pt-hNTs||Pt-hNTs ethanol electrolyzer only requires an electrolysis voltage of 0.40 V to achieve the electrochemical hydrogen production,demonstrating a highly energy saving strategy relative to traditional water electrolysis.

Bifunctional catalysts of Co3O4@GCN tubular nanostructured （TNS） hybrids for oxygen and hydrogen evolution reactions

Catalysts for oxygen and hydrogen evolution reactions （OER/HER） are at the heart of renewable green energy sources such as water splitting. Although incredible efforts have been made to develop efficient catalysts for OER and HER, great challenges still remain in the development of bifunctional catalysts. Here, we report a novel hybrid of Co3O4 embedded in tubular nanostructures of graphitic carbon nitride （GCN） and synthesized through a facile, large-scale chemical method at low temperature. Strong synergistic effects between Co3O4 and GCN resulted in excellent performance as a bifunctional catalyst for OER and HER. The high surface area, unique tubular nanostructure, and composition of the hybrid made all redox sites easily available for catalysis and provided faster ionic and electronic conduction. The Co3O4@GCN tubular nanostructured （TNS） hybrid exhibited the lowest overpotential （0.12 V） and excellent current density （147 mA/cm^2） in OER, better than benchmarks IrO2 and RuO2, and with superior durability in alkaline media. Furthermore, the Co3O4@GCN TNS hybrid demonstrated excellent performance in HER, with a much lower onset and overpotential, and a stable current density. It is expected that the Co3O4@GCN TNS hybrid developed in this study will be an attractive alternative to noble metals catalysts in large scale water splitting and fuel cells.

Electrocatalytic evolution of oxygen on NiCu particles modifying conductive alumina/nano-carbon network composite electrode

In this paper, a novel electrically conductive alumina/nano-carbon network (NCN) composite material was used as an electro- catalyst carrier. A NiCu/Al2O3 /NCN composite electrode was prepared by electrodepositing NiCu particles onto the surface of the conductive alumina/NCN composite. Morphology, composition, crystalline structure and electrochemical properties of the NiCu/Al2O3 /NCN composite electrode were investigated. The results showed that NiCu particles can be deposited onto the surface of the alumina/NCN composite by a coelectrodeposition method. NiCu particles in the form of solid solution with face-centered cubic (fcc) structure were relatively uniformly distributed over the carbon layer of the conductive ceramic between alumina grains. As-resulted NiCu/Al2O3 /NCN composite electrode had a remarkably enhanced electrochemical activity and high stabilization for oxygen evolution reaction, which indicated its potential application with enhanced performance to oxygen evolution reaction (OER). Moreover, based on the electrochemical measurement, the mechanism of the OER on the NiCu/Al2O3 /NCN composite electrode was discussed.