Tribological Behaviors of Electroless Nickel-Boron Coating on Titanium Alloy Surface

Titanium alloys are excellent structural materials in engineering fields,but their poor tribological properties limit their further applications.Electroless plating is an effective method to enhance the tribological performance of alloys,but it is difficult to efficiently apply to titanium alloys,due to titanium alloy’s strong chemical activity.In this work,the electroless Nickel-Boron(Ni-B)coating was successfully deposited on the surface of titanium alloy(Ti-6AL-4V)via a new pre-treatment process.Then,linearly reciprocating sliding wear tests were performed to evaluate the tribological behaviors of titanium alloy and its electroless Ni-B coatings.It was found that the Ni-B coatings can decrease the wear rate of the titanium alloy from 19.89×10^(−3)mm^(3)to 0.41×10^(−3)mm^(3),which attributes to the much higher hardness of Ni-B coatings.After heat treatment,the hardness of Ni-B coating further increases corresponding to coating crystallization and hard phase formation.However,heat treatment does not improve the tribological performance of Ni-B coating,due to the fact that higher brittleness and more severe oxidative wear exacerbate the damage of heat-treated coatings.Furthermore,the Ni-B coatings heat-treated both in air and nitrogen almost present the same tribological performance.The finding of this work on electroless coating would further extend the practical applications of titanium alloys in the engineering fields.

Continuous-flow electrosynthesis of urea and oxalic acid by CO_(2)-nitrate reduction and glycerol oxidation

Urea and oxalic acid are critical component in various chemical manufacturing industries.However,achieving simultaneous generation of urea and oxalic acid in a continuous-flow electrolyzer is a challenge.Herein,we report a continuous-flow electrolyzer equipped with 9-square centime-ter-effective area gas diffusion electrodes(GDE)which can simultaneously catalyze the glycerol oxidation reaction in the anode region and the reduction reaction of CO_(2) and nitrate in the cathode region,producing oxalic acid and urea at both the anode and cathode,respectively.The current density at low cell voltage(0.9 V)remained above 18.7 mA cm^(-2) for 10 consecutive electrolysis cycles(120 h in total),and the Faraday efficiency of oxalic acid(67.1%) and urea(70.9%)did not decay.Experimental and theoretical studies show that in terms of the formation of C-N bond at the cathode,Pd-sites can provide protons for the hydrogenation process of CO_(2) and NO_(3)^(-),Cu-sites can promote the generation of *COOH and Bi-sites can stabilize *COOH.In addition,in terms of glycerol oxidation,the introduction of Cu and Bi into Pd metallene promotes the oxidation of hydroxyl groups and the cleavage of C-C bond in glycerol molecules,respectively.

高熵合金金属烯用于酸性条件下全水分解

质子交换膜水电解槽(PEMWE)因其在低温下的高效率和高功率密度,成为新一代电解槽的发展方向.在水的电解过程中,设计高效稳定的析氢反应(HER)和析氧反应(OER)催化剂是进一步提高电解槽应用的前提.根据HER和OER“火山型”分布曲线,贵金属(Ir,Ru等)依然是主要的基准电催化剂.对于酸性条件下全水分解,Ir基和Ru基双功能催化剂仍然是最常见的选择.然而,与Ir基催化剂相比,Ru基催化剂在酸性条件下的高溶解速率易导致催化剂快速失活,大大降低了其实际应用价值.目前,酸性条件下全水分解的Ir基催化剂也取得了一些成果,如合金(如PdCu/Ir,Au@AuIr_(2),IrTe纳米棒和IrNi合金纳米花)、钙钛矿(如AIrO_(3))、硒化物(如Li-IrSe_(2))和团簇(如Ir纳米团簇,IrNi纳米团簇)等.然而,Ir基材料在高电流密度下仍然面临质量活性低和稳定性有限的挑战(100 mA cm^(-2)时的过电位超过420 mV,酸性整体水分解在高电流密度下的长期稳定性差).上述问题使得电催化剂无法满足PEMWE的应用要求.因此,开发具有优异电化学活性和稳定性的新型Ir基电催化剂成为当务之急.近年来,至少由五种元素组成的高熵合金(HEAs)材料具有在极端条件下的硬度、韧性、腐蚀性和热稳定性等的强耐受性,因而引起了研究者的广泛兴趣.同时,不同组分的可控性也赋予了HEAs固有的晶格畸变和可调电子结构的协同效应,在催化领域也发挥着重要作用.目前,尚未见使用HEAs催化剂进行酸性条件下全水分解的相关报道.从形貌上看,金属烯具有表面金属原子体积比大、表面金属缺陷丰富、稳定性较好等优点,从而表现出较好的催化性能.因此,结合HEAs协同效应和金属烯结构优点的电催化剂,有望解决酸性条件下全水分解电催化剂的设计问题.本文成功制备了具有丰富的无定形和晶体结构的IrPdRhMoW HEA金属烯作为一种高效的双功能电催化剂,用于酸性条件下全水分解.在0.5 mol L^(-1)H_(2)SO_(4)溶液中,IrPdRhMoW/C在10 mA cm^(-2)下HER和OER的过电位分别为15和188 mV,远强于商业催化剂(HER:Pt/C,47 mV和OER:RuO_(2),305 mV)和大部分已报道的贵金属基催化剂.使用IrPdRhMoW/C进行全水分解,只需1.48 V的电池电压即可获得10 mA cm^(-2)的电流密度,而实现100 mA cm^(-2)的电流密度所需的电池电压为1.59 V.IrPdRhMoW/C在100 mA cm^(-2)水分解100 h后仍保持较好的电活性和结构稳定性,这也是在高电流密度下实现酸性条件下全水分解的长期稳定性.密度泛函理论计算结果表明,由于晶体和非晶结构的共存,HEA中电子结构的具有自平衡效应.强轨道耦合不仅最大限度地提高了对HER和OER的电活性,而且稳定了金属位点的价态,以实现持久的电催化全水分解.综上,本工作不仅成功制备了HEA金属烯,而且将其应用于酸性条件下全水分解.此外,电荷自平衡效应可以解决酸性条件下全水分解过程中活性与稳定性之间的问题,且有望进一步应用到其他电催化剂的设计和合成中.

局部氧自由基的性质促进电催化乙醇选择性生成CO_(2)

碱性燃料电池可以避免卡诺循环效应的限制,因而被认为是最具有发展潜力的能源转换器件之一.与其它燃料相比,乙醇来源丰富,储存和运输成本较低,更适合作为燃料电池的能量来源.但在乙醇氧化反应(EOR)过程中,通常发生2个或6个电子转移的不完全氧化反应,而不是转移12个电子的完全氧化过程.除催化剂对C-C键裂解能力较低外,中间体对催化剂的毒化也是造成乙醇不能被完全氧化的原因.大量研究表明,增强催化剂对OH*和O*的吸附可以有效促进C-C键的裂解并提高催化剂的抗毒化性能.然而,不同氧物种对C-C键裂解的作用尚不明确.本文将人工氧化酶应用在EOR中,并在此基础上探究了不同氧自由基在乙醇氧化过程中的作用.本文发现一种可以催化氧气原位生成活性氧物种(ROS)的人工氧化酶,并利用该特点,将人工氧化酶应用于EOR中,同时探究了不同ROS在乙醇完全氧化中的作用.当没有ROS时,催化剂的质量活性为7.6 A mg_(Pt)^(-1),二氧化碳的法拉第效率仅为12.4%;而在ROS的作用下,催化剂的质量活性可以达到18.2 A mg_(Pt)^(-1),二氧化碳的法拉第效率达到98.7%.这说明ROS的存在有助于提升催化剂活性和二氧化碳选择性.与PtSn IM/C相比,商业Pt/C只能生成少量的羟基自由基,没有检测到单线态氧和超氧阴离子,表明Sn元素的引入可以优化Pt的电子结构,并改善催化剂的表面配位方式,提高催化剂的氧化酶活性.利用原位红外测试技术研究了反应过程中生成的中间体和催化剂整体性能,结果表明,在ROS作用下催化剂表面没有生成有毒的*CO中间体,说明ROS显著提升了催化剂的抗毒化性能.另外,经过8次电解液的更新,二氧化碳的选择性没有发生明显衰减,表明ROS可以增强催化剂的耐久性.CO剥离实验结果表明,在ROS的作用下,催化剂对CO的氧化电位降低了46mV,进一步证明ROS可以有效避免催化剂被中间产物毒化.为进一步研究反应的机理,对体系中生成的ROS进行了电子顺磁共振测试.结果表明,PtSn IM/C可以催化氧气原位生成大量的·OH,·O_(2)~-和~1O_(2).通过向体系中加入不同的自由基捕获剂探究不同氧物种对EOR活性和C-C键裂解的影响.结果表明,单线态氧可以显著提升催化剂活性和C-C键的裂解能力.理论计算结果表明,*CH_(3)CO的C-C键断裂产生*CH_(3)和*CO是Cl途径的决速步骤.当单线态氧存在于PtSn IM/C表面上时,C-C键的离解能为-0.51 eV,低于羟基自由基的1.07 eV和超氧阴离子的-0.47 eV.综上所述,乙醇燃料电池是未来最具有潜力的能源转换器件之一.本研究为乙醇燃料电池阳极催化剂的设计提供了一种新思路.本研究还为探究氧自由基在乙醇氧化反应中的作用和用于多元醇完全氧化反应的催化剂的制备提供参考.

Scalable synthesis of ultra‐small Ru_(2)P@Ru/CNT for efficient seawater splitting

In this study,an ultra‐fast and simple solvent‐free microwave method was successfully demonstrated using a series of ultra‐small(~2.5 nm)surfactant‐free Ru_(2)P@Ru/CNT heterostructures for the first time.The structure has a high‐density Ru component and Ru_(2)P component interface,which accelerates the hydrogen evolution reaction(HER).The prepared Ru_(2)P@Ru/CNT demonstrated excellent catalytic effects for the HER in alkaline media and real seawater.The experimental results indicate that ratio‐optimized Ru_(2)P@Ru/CNT(Ru_(2)P:Ru=66:34)requires only 23 and 29 mV to reach 10 mA cm^(-2)in 1.0 mol/L KOH and real seawater,respectively.These values are 10 and 24 mV lower than those of commercial Pt/C in 1.0 mol/L KOH(33 mV)and real seawater(53 mV),respectively,making it among the best non‐Pt HER reported in the literature.Additionally,the TOF of Ru_(2)P@Ru/CNT in alkaline freshwater and seawater were 13.1 and 8.5 s^(-1),respectively.These exceed the corresponding values for Pt/C,indicating that the catalyst has excellent intrinsic activity.The high current activity of Ru_(2)P@Ru/CNT in 1.0 mol/L KOH was explored,and only 77 and 104 mV were required to reach 500 and 1000 mA cm^(-2),respectively.After 100 h of durability testing,the catalyst retained excellent catalytic and structural stability in low current density,high current density,and seawater.

Ultra-fast phosphating synthesis of metastable crystalline phase-controllable ultra-small MPX/CNT(M = Pd, Pt, Ru) for polyalcohol electrooxidation

A general approach is reported for ultra-fast phosphating synthesis of a series of ultra-small(<5 nm)noble metal phosphides(MPX/CNT,M=Pd,Pt,Ru)which are successfully produced in just 75 s for the first time.The catalytic performance of the catalysts can be optimized by controlling the nanomaterials as the metastable crystalline phases.By altering the phosphorus source under the same conditions,the hexagonal structured Pd_(7)P_(3)(NaH_(2)PO_(2).H_(2)O as P source)and monoclinic structured Pd_(6)P(Na_(4)P_(2)O_(7) as P source)can be prepared successfully.Both of them exhibit excellent polyol oxidation performance in alkaline media.Monoclinic Pd_(6)P/CNT and hexagonal Pd_(7)P_(3)/CNT have large ECSA which are confirmed as 82.1 m2 g^(-1)and 86.2 m2 g^(-1),respectively.Hexagonal Pd_(7)P_(3)/CNT has the highest mass activity of 6.14 A mgPd^(-1)(3.21 A mgPd^(-1)for Pd_(6)P/CNT)for GOR,which far exceeded Pt/C(2.81 A mgPt^(-1)).Meanwhile,the mass activity of monoclinic Pt_(5)P_(2)/CNT for EGOR achieved 12.4 A mg_(Pt)^(-1),which far exceeded Pt/C(6.8 A mg_(Pt)^(-1)).The stability test proved that the activity decay of these catalysts was negligible after the 12-hour durability test.Meanwhile,they have excellent CO anti-poisoning abilities.

Polysulfide modified PtCu intermetallic nanocatalyst with enrichment realizes efficient electrooxidation ethanol to CO_(2)

The main problem faced by ethanol oxidation reaction(EOR)includes low activity,poor selectivity,and durability.In the study,we found that polysulfide modified on the surface of PtCu intermetallic(IM)/C can simultaneously enrich hydroxyl and ethanol,which could effectively improve the catalytic activity,CO_(2) selectivity,and durability of catalyst.The mass activity and the specific activity of the product in 1 M KOH electrolyte reached 17.83 A·mgPt^(-1) and 24.67 mA·cm^(-2).The CO_(2) selectivity of polysulfide modified product achieved 93.5%,which was 30 folds higher than Pt/C.In addition,the catalyst showed high catalytic stability.The mechanism study demonstrates that the surface modified polysulfide could significantly boost the enrichment effect of ethanol and hydroxyl species,accelerating C–C bond cleavage and CO oxidation.

Acidic electroreduction CO_(2)to formic acid via interfacial modification of Bi nanoparticles at industrial-level current

Electrocatalytic CO_(2)reduction reaction(CO_(2)RR)in acidic media is a promising approach to overcome the unavoidable formation of carbonates in alkaline or neutral electrolytes.However,the proton-rich environment near the catalyst surface favors hydrogen evolution reactions(HER),leading to lower energy efficiency of the desired products,especially in industrial-level current densities.Here,quaternary ammonium cationic surfactant(cetyltrimethylammonium bromide(CTAB))was introduced into acidic electrolyte to modulate the interfacial microenvironment,which greatly enhanced CO_(2)electroreduction to formic acid(HCOOH)at the Bi/C nanoparticles electrode.Using a Bi/C nanoparticles electrode with CTAB added,constant production of formic acid was enabled with a cathodic energy efficiency of>40%and maximum FE_(HCOOH)(FE=Faradaic efficiency)of 86.2%at−400 mA·cm^(−2)over 24 h.Combined with in-situ attenuated total reflection Fourier transform infrared spectroscopy,the concentration of*OCHO intermediates significantly increased after CTAB modification,confirming that the hydrophobic interface microenvironment formed by dynamic adsorption of positively charged long alkyl chains on Bi/C nanoparticle electrodes inhibited HER and improved the selectivity of CO_(2)RR to HCOOH.

Regulate electric double layer for one-step synthesize and modulate the morphology of(oxy)hydroxides

FeOOH have received considerable attention due to their natural abundance and cost-effectiveness.Despite the significant progress achieved,the one-step synthesis of integrated FeOOH is still a major challenge.Meanwhile,the current research on FeOOH catalyst still suffers from the unclear mechanism of controlling morphology.Here,density functional theory(DFT)calculations and X-ray photoelectron spectroscopy(XPS)demonstrated the strong electron-capturing and hydrogen absorption ability of Co in FeOOH,which further promotes the formation and stabilization of FeOOH.We used a one-step electrodeposition method to synthesize Co introduced FeOOH integrated electrocatalyst and propose to introduce ions with different valence states to regulate the morphology of FeOOH by precise modulation of electric double layer(EDL)composition and thickness.The prepared Co-FeOOH-K^(+)has a larger electrochemically active surface area(ECSA)(325 cm^(2))and turnover frequency(TOF)value(0.75 s^(-1)).In the electrochemical experiments of an alkaline anion exchange membrane electrolyzer,Co-FeOOH-K^(+)shows better oxygen evolution performance than commercial RuO_(2) under industrial production conditions and has good industrial application prospects.

Face-to-face engineering of ultrathin Pd nanosheets on amorphous carbon nitride for efficient photocatalytic hydrogen production

Photocatalytic hydrogen production represents a promising strategy for clean, sustainable, and environmentfriendly energy supply. Up to now, great efforts have been devoted to designing the photocatalysts with noble metal as co-catalyst for visible-light-driven hydrogen evolution, while more efficient photocatalytic systems are still a major challenge. Herein, we report a facile strategy for synthesizing faceto-face ultrathin Pd nanosheets-amorphous carbon nitride(Pd NSs-ACN) structure with large contacting interface and short electronic transmission pathway, which can work as an efficient photocatalyst for hydrogen production. The synthesis starts with the growth of ultrathin Pd NSs, followed by assembly with the visible-light-response ACN through a simple stirring and annealing procedure. The resultant two dimensional face-to-face structures deliver an average hydrogen generation rate of 1.45 mmol h-1g-1 at a temperature of 25℃,almost 2.6 times higher than that of Pd Nps-ACN with particle-to-face structural feature. The efficient photocatalytic activity is ascribed to the formation of high-density of active sites between ultrafine face-to-face contacted Pd NSs and the ACN, which cooperate more synergistically towards photocatalytic hydrogen production. The face-to-face engineered Pd NSs-ACN hybrids also offer a good stability revealed by photocatalytic hydrogen production measurements. The extraordinary performance highlights a powerful engineering model for designing other face-to-face contacting co-catalyst/photocatalysts, which will be a great impetus to optimize new catalytic transformations.

Designing noble metal single-atom-loaded two-dimension photocatalyst for N2 and CO2 reduction via anion vacancy engineering

Building highly active and stable noble metal single atom(MSA)catalyst onto photocatalyst materials for nitrogen reduction reaction(NRR)and CO2 reduction reaction(CRR)is a key to future renewable energy conversion and storage technologies.Here we present a design strategy to optimize the stability and electronic property of noble metal single atoms(MSAs,M=Rh,Pd,Ag,Ir,Pt,Au)catalyst supported on g-C3N4 and 2H-MoS2 photocatalysts towards NRR and CRR.Our results indicate that the MSAs tend to be trapped at the anion-vacancy sites of photocatalyst rather than the pristine photocatalyst surface.This anion vacancy can promise the MSAs with an optimized electron-captured ability in the photoexcitation process,thus decreasing the energy barriers of NRR and CRR on MSAs.Especially,it is revealed that the N-vacancy-stabilized Ir SA on g-C3N4 and the S-vacancy-stabilized RhSA on 2H-MoS2 own the lowest energy barrier in NRR.However,for CRR,the HCOOH is the main product on MSAs supported by gC3N4 and 2H-MoS2.The N-vacancy-stabilized PdSA on g-C3N4 and the S-vacancy-stabilized AuSA on 2H-MoS2 show the lowest energy barrier for HCOOH production in CRR.This finding offers an approach to design specific active MSA centres on photocatalysts by the anion vacancy engineering.

Strong High Entropy Alloy-Support Interaction Enables Efficient Electrocatalytic Water Splitting at High Current Density

In electrocatalysis, the stability issue between catalyst and support still needs great attention. Here, a series of highentropy alloy nanoparticles(HEA-NPs) embedded in carbon cloth(CC) were synthesized by using the scalable strategy-microwave heating. Among them, PtRhCoNiCu/CC exhibits outstanding hydrogen evolution reaction(HER) activity(19 and 170 mV overpotential at 10 and 1000 mA cm^(-2)) and stability(150 h), outperforming other recently reported HEAs catalysts. IrRuCoNiCu/CC displays superior oxygen evolution reaction(OER) activity(166 and 354 mV overpotential at 10 and 1000 m A cm^(-2)) and stability(150 h), and shows a lower overpotential than recently reported HEA catalysts. In water splitting, IrRuCoNiCu/CC(+)//Pt Rh Co Ni Cu/CC(-) electrolyzer achieves 500 m A cm^(-2)(1000 m A cm^(-2)) high current density at 1.76 V(1.88 V) and exhibits excellent stability, which is one of the best catalysts currently. Therefore, the novel supported HEA catalyst with high stability is expected to be a promising candidate material for industrialized water splitting.

Reduction-induced interface reconstruction to fabricate MoNi_(4) - based hollow nanorods for hydrazine oxidation assisted energysaving hydrogen production in seawater

Seawater electrolysis could address the water scarcity issue and realize the grid-scale production of carbon-neutral hydrogen,while facing the challenge of high energy consumption and chloride corrosion.Thermodynamically more favorable hydrazine oxidation reaction(HzOR)assisted water electrolysis is efficiency for energy-saving and chlorine-free hydrogen production.Herein,the MoNi alloys supported on MoO_(2) nanorods with enlarged hollow diameter on Ni foam(MoNi@NF)are synthesized,which is constructed by limiting the outward diffusion of Ni via annealing and thermal reduction of NiMoO_(4) nanorods.When coupling HzOR and hydrogen evolution reaction(HER)by employing MoNi@NF as both anode and cathode in two-electrode seawater system,a low cell voltage of 0.54 V is required to achieve 1,000 mA·cm^(−2) and with long-term durability for 100 h to keep above 100 mA·cm^(−2) and nearly 100%Faradaic efficiency.It can save 2.94 W·h to generate per liter H_(2) relative to alkaline seawater electrolysis with 37%lower energy equivalent input.

Coordination engineering of cobalt phthalocyanine by functionalized carbon nanotube for efficient and highly stable carbon dioxide reduction at high current density

Coordination engineering can enhance the activity and stability of the catalyst in heterogeneous catalysis.However,the axial coordination engineering between different groups on the carbon carrier and molecular catalysts in the electrocatalytic carbon dioxide reduction reaction(CO_(2)RR)has been studied rarely.Through coordination engineering strategy,a series of amino(NH_(2)),hydroxyl(OH),and carboxyl(COOH)groups functionalized carbon nanotubes(CNT)immobilized cobalt phthalocyanine(CoPc)catalysts are designed.Compared with no groups,OH groups and COOH groups,NH_(2)groups can effectively change the coordination environment of the central metal Co,thereby significantly increasing the turnover frequency(TOF)(31.4 s^(-1)at-0.6 V vs.RHE,CoPc/NH_(2)-CNT>CoPc/OH-CNT>CoPc/COOH-CN>CoPc/CNT).In the flow cell,the CoPc/NH_(2)-CNT catalyst has high carbon monoxide(CO)selectivity at high current density(~100%at-225 mA·cm^(-2),~96%at-351 mA·cm^(-2)).Importantly,the CoPc/NH_(2)-CNT catalyst can operate stably for 100 h at 225 mA·cm^(-2).Theoretical calculations reveal that CoPc/NH_(2)-CNT catalyst is beneficial to the formation of^(*)COOH and desorption of^(*)CO,thus promoting CO_(2)RR.This work provides an excellent platform for understanding the effect of coordination engineering on electrocatalytic performance and promotes a way to explore efficient and stable catalysts in other applications.

BiOCl/ultrathin polyaniline core/shell nanosheets with a sensitization mechanism for efficient visible-light-driven photocatalysis

Photocatalytic technology holds great promise in renewable energy and environmental protection.Herein,we report the synthesis of a class of polyaniline-sensitized BiOCI core/shell nanosheets with visible-light photocatalytic activity by a one-step oxidative polymerization method and show how the hybrid nanosheet boosts the photocatalytic activity and stability for degradation of Rhodamine B (RhB).In this unique structure,the ultrathin polyaniline (PANI)as a shell with the thickness of about 1-2nm,can widen the response of the catalyst to visible light to boost photocatalysis and the BiOCI core can promote the separation of photogenerated carriers from the PANI.We demonstrate that the optimized BiOCl/ PANI core/shell photocatalyst shows nearly three times higher photocatalytic activity for the degradation of RhB than pure BLOC1and also shows high stability.This work provides a new strategy for the design of a highly efficient hybrid photo- catalyst driven by visible light.

Revealing the relationships between alloy structure,composition and plastic deformation in a ternary alloy system by a combinatorial approach

A high-throughput approach based on magnetron co-sputtering of alloy libraries is employed to investigate mechanical properties of crystalline and amorphous alloys in a ternary palladium(Pd)-tungsten(W)-silicon(Si)system with the aim to reveal the difference in plastic deformation response and extract the relevant structure-property relationships of the alloys in the system.It was found that in contrast to crystalline alloys,the amorphous ones,i.e.,metallic glasses,exhibited a much smaller fluctuation range in the plasticity parameters(Er2/H and Wp/Wt),indicating a significant difference in the plastic deformation mechanism controlling the mechanical properties for the respective alloys.We propose that the inhomogeneous deformation of amorphous alloys localized in thin shear bands is responsible for the weaker compositional dependence of both plasticity parameters,while dislocation gliding in crystalline materials is significantly more dependent on the exact structure,thus resulting in a larger scattering range.Based on the representative efficient cluster packing model,a set of composition-dependent atomic structural models is proposed to figure out the structure-property relationships of amorphous alloys in Pd-W-Si alloy system.

Amorphous/2H-MoS_(2) nanoflowers with P doping and S vacancies to achieve efficient pH-universal hydrogen evolution at high current density

Molybdenum disulfide(MoS_(2))has become a competitive candidate for efficient and economical hydrogen evolution reaction(HER).Compared with 1T-MoS_(2),2H-MoS_(2) possesses exceptional thermodynamic stability but still suffers from low active site density,poor conductivity,and weak hydrogen bonding in the wide pH range.Herein,2H-MoS_(2) nanoflowers with phosphorus doping,sulfur vacancies and crystalline-amorphous heterojunction were synthesized via phosphorus-assisted rapid calcination method.Benefiting from the cooperative interaction of multiple strategies,the prepared 2H-MoS_(2) nanoflowers firstly achieve efficient pH-universal HER at high current densities.Experimental results show that in alkaline,acidic,and neutral media,MoS_(2)-P2 requires only 332,302,and 417 mV to drive the current density of 500 mA cm^(−2) and obtains 932,1100,and 472 mA cm^(−2) at the potential of−0.4 V vs.RHE,respectively.Moreover,MoS_(2)-P2 shows excellent stability of low and high current density in the full pH range.

Noble metal aerogels rapidly synthesized by ultrasound for electrocatalytic reaction

Noble metal aerogels(NMAs), belonging to the porous material, have exhibited excellent catalytic performance. Although the synthesis method continues to improve, it still exists some problems which hindered the experimental process, such as high concentration of noble metal precursors, long synthesis cycle, expensive production cost, and uncontrollable ligament length. In this work, ultrasonic wave and reducing agent Na BH;were simultaneously applied to gelation process. With the cavitation of ultrasound,it can generate huge energy with heating and stirring, thus gelation reaction proceeded quickly, and even completed the process in only a few seconds, that is much faster than the recorded. A wide concentration range was successfully expanded from 0.02 mmol/L to 62.5 mmol/L. Further, we extended this method to a variety of noble metal elements(Au, Ru, Rh, Ag, Pt, Pd), and this method is adaptive for the synthesis of single metal aerogels(Au, Ag, Ru, Rh, Pd), bimetal and trimetal aerogels(Au-Ag, Au-Rh, Au-Ru, Au-Pt,Au-Pd, Au-Pt-Pd). In addition, the ligament size of alloy aerogels are 10 nm or less. Moreover, their brilliant properties were demonstrated in hydrogen evolution reaction(HER) and ethanol oxidation reaction(EOR).

Superfast tellurizing synthesis of unconventional phase-controlled small Pd-Te nanoparticles

Large-scale production of unconventional phase-controlled telluride catalysts in a simple and fast manner still poses a great challenge.Herein,we develop a superfast tellurizing synthesis method that can quickly prepare unconventional phase-controlled palladium telluride nanoparticles(Pd-Te NPs)on carbon nanotubes(CNTs)(i.e.,PdTe/CNT,Pd_(20)Te_(7)/CNT)in 60 s.By merely tuning the mass of the tellurium precursors under the same conditions,fine(about 5.5 nm)and high-yield(about 90%)hexagonal structured PdTe/CNT and rhombohedral structured Pd_(20)Te_(7)/CNT can be precisely synthesized.The hexagonal structured PdTe/CNT exhibits excellent performance for glycerol oxidation reaction(GOR)and ethylene glycol oxidation reaction(EGOR).Specifically,the highest current density for GOR is 2.72 A mgPd^(-1),which is 1.9-fold higher than that of rhombohedral structured Pd_(20)Te_(7)/CNT,and 2.8-fold higher than that of Pd/CNT.It also outperforms most catalysts reported in GOR.Meanwhile,the specific activity for EGOR is 3.65 A mgPd^(-1),which is 2.1 and 3.9 times higher than those of rhombohedral structured Pd_(20)Te_(7)/CNT and Pd/CNT.We hope that this work can provide guidance for the preparation of crystalline phase-controlled telluride catalysts via new tellurization and inspire the application of crystalline phasecontrolled materials.

Boric Acid-Based Dual Modulation Photoluminescent Glucose Sensor Using Thioglycolic Acid-Capped CdTe Quantum Dots

Most luminescent glucose sensors based on the interaction of glucose with organic boric acids or borates.Herein,a new luminescent glucose sensor is designed using thioglycolic acid-capped CdTe quantum dots in the presence of cheap inorganic boric acid.Both peak position and intensities change upon the addition of glucose because of the interaction of boric acid with glucose and thioglycolic acid-capped CdTe quantum dots,which enables glucose detection by either color change or intensity change.The luminescent intensities change linearly with glucose concentrations in the ranges from 0.03 to 1 mM and 1–25 mM with a detection limit of 10μM(S/N=3).Moreover,glucose concentrations can be conveniently detected by color change in the range from 1 mM–25 mM.It displays a highly selective response to glucose over other interfering but biologically important saccharides,amino acids,and common ions.Graphical Abstract A thioglycolic acid-capped CdTe QD-based sensor can detect glucose with wide linear range by change in intensity or color in the presence of cheap inorganic boric acid.