查看更多>>摘要：Tunable behavior in electrocatalysis by external multifields,such as magnetic field,thermal field,and electric field,is the most promising strategy to expand the theory,design,and synthesis of state-of-the-art catalysts and the cell in the near future.Here,a systematic investigation for the effect of external magnetic field and thermal field on methanol oxidation reactions(MOR)in magnetic nanoparticles is reported.For Co42Pt58 truncated octahedral nanoparticles(TONPs),the catalytic performance in MOR is greatly increased to the maximum of 14.1％by applying a magnetic field up to 3000 Oe,and it shows a monotonical increase with increasing working temperature.The magnetic enhanced effect is closely related to the Co content of CoxPt100-x TONPs.Furthermore,the enhancement effect under a magnetic field is more obvious for Co42Pt58 TONPs annealed at 650 ℃.First-principle calculation points out that the magnetic fields can facilitate the dehydrogenation of both methanol and water by suppression of entropy of the electron spin and lowering of the activation barrier,where OHad intermediates on Co sites play a more important role.The application of magnetic fields together with thermal fields in MOR provides a new prospect to manipulate the performance of direct methanol fuel cells,which will accelerate their potential applications.
查看更多>>摘要：LiNi0.8Co0.1Mn0.1O2(NCM811)| SiOx-graphite(SiO-Gr.)battery chemistry is of intensive attention because its achievable practical energy density is approaching impressively 300 Wh Kg-1.However,it still suffers rapid capacity fades during repeated cycles,both chemical,electrochemical and mechanical irreversibility contribute.A comprehensive understanding behind the fading behavior of the cell chemistry is required before fully realize the benefits of this chemistry.Herein,the in-situ thickness variation is introduced as a diagnostic technique and is performed on 5-55 Ah NCM811|SiO-Gr cells.With the help of Li reference electrode and in-situ X-ray diffraction device,the correspondence between thickness variation and the electrode potential is carefully investigated.Firstly,the NCM811|SiO-Gr cell is characterized with the maximum cell thickness at around 80％state-of-charge(SOC)in the discharge process,rather than at 100％SOC.Secondly,the electrochemical behaviors during rate charge/discharge are diagnosed,and a Li platting signal is resolved from thickness variation profile at 2C.This work confirms that the thickness monitoring is a nondestructive and informative complement to conventional diagnostic techniques for failure analysis of pouch cells.
查看更多>>摘要：Understanding the effect of additive on the interfacial charge-carrier transfer dynamics is very crucial to obtaining highly efficient perovskite solar cells(PSCs).Herein,we designed a simple additive,dimethyl oxalate(DO),functioning as an effective defect passivator of perovskite grain boundaries via the coordination interaction between the carbonyl(C=O)and the exposed Pb2+.The modification with DO produces pinhole-free and compact perovskite films,enhancing the transportation capability of carriers.As a consequence,the DO-treated PSCs exhibited a power conversion efficiency(PCE)of 22.19％,which is significantly higher than that of the control device without additive(19.58％).More importantly,detailed transient absorption characterization reveals that the use of additive can decrease the hot-carrier cooling dynamics,improve the carrier transfer,and eliminate nonradiative recombination in PSCs.This present work provides a profound understanding the additives effect on the carrier dynamics in PSCs toward the Shockley-Queisser limit.
查看更多>>摘要：Water splitting is important to the conversion and storage of renewable energy,but slow kinetics of the oxygen evolution reaction(OER)greatly limits its utility.Here,under visible light illumination,the p-n WO3/SnSe2(WS)heterojunction significantly activates OER catalysis of CoFe-layered double hydroxide(CF)/carbon nanotubes(CNTs).Specifically,the catalyst achieves an overpotential of 224 mV at 10 mA cm-2 and a small Tafel slope of 47 mV dec-1,superior to RuO2 and most previously reported transition metal-based OER catalysts.The p-n WS heterojunction shows strong light absorption to produce photogenerated carriers.The photogenerated holes are trapped by CF to suppresses the charge recombination and facilitate charge transfer,which accelerates OER kinetics and boost the activity for the OER.This work highlights the possibility of using heterojunctions to activate OER catalysis and advances the design of energy-efficient catalysts for water oxidation systems using solar energy.
查看更多>>摘要：Herein,a simple synthetic approach is employed for the atomic dispersion of Rh atoms(Rh SAs)over the surface of interconnected Mo2C nanosheets intimately embedded in a three-dimensional NixMoOy nanorod arrays(NixMoOy NRs)framework;we found that the introduction of both isolated Rh SAs and NixMoOy NRs adjusts the electrocatalytic function of the host Mo2C toward the direction of being an advanced and highly stable electrocatalyst for efficient hydrogen evolution at pH-universal conditions.As a result,the proposed catalyst outperforms most recently reported transition metal-based catalysts,and its performance even rivals that of commercial Pt/C,as demonstrated by its ultralow overpotentials of 31.7,109.7,and 95.4 mV at a current density of 10 mA cm-2,along with its small Tafel slopes of 42.4,51.2,and 46.8 mV dec-1 in acidic,neutral,and alkaline conditions,respectively.In addition,the catalyst shows remarkable long-term stability over all pH values with good maintenance of its catalytic activity and structural characteristics after continuous operation.
查看更多>>摘要：Perovskite solar cells(PSCs)have been demonstrated to be one of the most promising technologies in the field of renewable energy.However,the presence of the defects in the perovskite films greatly limits the efficiency and the stability of the PSCs.The additive engineering is one of the most effective approaches to overcome this problem.Most of the successful additives are extracted from the petroleum-based materials,while the research on the biomass-based additives is still lagging behind.In this paper,two ecofriendly hydroxyalkyl cellulose additives,i.e.,hydroxyethyl cellulose(HEC)and hydroxylpropyl cellulose(HPC),are investigated on the performance of the MAPbl3-based inverted PSCs.Due to the strong interaction between the hydroxyl groups of the cellulose and the divalent cations of the perovskite,these additives enhance the crystal grain orientation and significantly repair the defects of the perovskite films.Working as the additives,these two cellulose derivatives show a strong passivation ability,which significantly reduces the trap density and improves the optoelectronic feature of the PSCs.Compared with the average power conversion efficiency(PCE)of the control device(19.19％),an enhancement of～10％is achieved after the addition of HEC.The optimized device(PCE=21.25％)with a long-term stability(10:80 h,PCE=20.93％)is achieved by the incorporation of the HEC additives into the precursor solution.It is the best performance among the PSCs with the cellulose additives up to now.This research provides a novel choice to develop a cost-effective and renewable additive for the PSCs with high efficiency and excellent long-term stability.
查看更多>>摘要：The development of high-performance binders is a simple but effective approach to address the rapid capacity decay of high-capacity anodes caused by large volume change upon lithiation/delithiation.Herein,we demonstrate a unique organic/inorganic hybrid binder system that enables an efficient in situ crosslinking of aqueous binders(e.g.,sodium alginate(SA)and carboxymethyl cellulose(CMC))by reacting with an inorganic crosslinker(sodium metaborate hydrate(SMH))upon vacuum drying.The resultant 3D interconnected networks endow the binders with strong adhesion and outstanding self-healing capability,which effectively improve the electrode integrity by preventing fracturing and exfoliation during cycling and facilitate Li+ion transfer.SiO anodes fabricated from the commercial microsized powders with the SA/0.2SMH binder maintain 1470 mAh g-1 of specific capacity at 100 mA g-1 after 200 cycles,which is 5 times higher than that fabricated with SA binder alone(293 mAh g-1).Nearly,no capacity loss was observed over 500 cycles when limiting discharge capacity at 1500 mAh g-1.The new binders also dramatically improved the performance of Fe2O3,Fe3O4,NiO,and Si electrodes,indicating the excellent applicability.This finding represents a novel strategy in developing high-performance aqueous binders and improves the prospect of using high-capacity anode materials in Li-ion batteries.
查看更多>>摘要：Highly sensitive and uniform three-dimensional(3D)hybrid heterogeneous structures for use in surface-enhanced Raman scattering(SERS)experiments were fabricated by sequentially decorating high-quality,ultra-clean,graphene quantum dots(GQDs)and Ag nanoparticles(Ag-NPs)onto 3D-graphene.Finite-difference time-domain calculations and scanning Kelvin probe microscopy were used to verify that the Ag-NPs/GQDs/3D-graphene system facilitates substantial electromagnetic enhancement(due to the occurrence of two kinds of"gaps"between the Ag-NPs that form 3D"hot spots")and additional chemical enhancement(in detecting some π-conjugated molecules).The SERS mechanism was explored in further detail via experimental analysis and confirmed by performing theoretical calculations.The large surface area of the 3D substrate(due to the large specific surface areas of the GQDs and 3D-graphene)results in a better enrichment effect which helps produce lower detection limits.In particular,the detection limits obtained using the Ag-NPs/GQDs/3D-graphene platform can reach 10-11 M for rhodamine 6G,10-10 M for methylene blue and dopamine,and 10-7 M for tetramethylthiuram disulfide and methyl parathion in apple juice(these are superior to most of the results reported using graphene-based SERS substrates).In summary,the 3D-platform Ag-NPs/GQDs/3D-graphene/Si shows outstanding SERS performance.It therefore has excellent application prospects in biochemical molecular detection and food safety monitoring.
查看更多>>摘要：Implementing high-performance silicon(Si)anode in actual processing and application is highly desirable for next-generation,high-energy Li-ion batteries.However,high content of inactive matrix(including conductive agent and binder)is often indispensable in order to ensure local conductivity and suppress pulverization tendency of Si particles,which thus cause great capacity loss based on the mass of whole electrode.Here,we designed an accordion-structured,high-performance electrode with high Si content up to 95％.Si nanoparticles were well anchored into the interlayer spacings of accordion-like graphene arrays,and free-standing electrode was prepared via a simple filtration process without any binder.Conductive accordion framework ensures strong confinement effect of Si nanoparticles and also provides direct,non-tortuous channels for fast electrochemical reaction kinetics.As a consequence,the accordion Si electrodes exhibit ultrahigh,electrode-based capacities up to 3149 mAh g-1(under Si content of 91％),as well as long-term stability.Also,the accordion electrode can bear extreme condition of over-lithiation and maintains stable in full-cell test.This design provides a significant stride in high Si content toward realistic,high-performance electrodes.
查看更多>>摘要：Rational design and construction of highly efficient nonprecious electrocatalysts for oxygen reduction and alcohols oxidation reactions(ORR,AOR)are extremely vital for the development of direct oxidation alkaline fuel cells,metal-air batteries,and water electrolysis system involving hydrogen and value-added organic products generation,but they remain a great challenge.Herein,a bifunctional electrocatalyst is prepared by anchoring CuS/NiS2 nanoparticles with abundant heterointerfaces and sulfur vacancies on graphene(Cu1Ni2-S/G)for ORR and AOR.Benefiting from the synergistic effects between strong interfacial coupling and regulation of the sulfur vacancies,Cu1Ni2-S/G achieves dramatically enhanced ORR activity with long term stability.Meanwhile,when ethanol is utilized as an oxidant for AOR,an ultralow potential(1.37 V)at a current density of 10 mA cm-2 is achieved,simultaneously delivering a high Faradaic efficiency of 96％for ethyl acetate production.Cu1Ni2-S/G also exhibits catalytic activity for other alcohols electrooxidation process,indicating its multifunctionality.This work not only highlights a viable strategy for tailoring catalytic activity through the synergetic combination of interfacial and vacancies engineering,but also opens up new avenues for the construction of a self-driven biomass electrocatalysis system for the generation of value-added organic products and hydrogen under ambient conditions.
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