The development of highly active nitrogendoped carbon-based transition metal(M-N-C)compounds for the oxygen reduction reaction(ORR)in proton exchange membrane fuel cells(PEMFCs)greatly helps reduce fuel cell cost,thus...
详细信息
The development of highly active nitrogendoped carbon-based transition metal(M-N-C)compounds for the oxygen reduction reaction(ORR)in proton exchange membrane fuel cells(PEMFCs)greatly helps reduce fuel cell cost,thus rapidly promoting their commercial *** different M-N-C electrocatalysts,the series of Fe-N-C materials are highly favored because of their high ORR ***,there remains a debate on the effect of Fe,and rare investigations focus on the influence of Fe addition in the second heat treatment usually performed after acid leaching in the catalyst *** is thus very critical to explore the influences of Fe on the ORR electrocatalytic activity,which will,in turn,guide the design of Fe-N-C materials with enhanced ***,a series of Fe-N-C electrocatalysts are synthesize and the influence of Fe on the ORR activity are speculated both experimentally and *** is deduced that the active site lies in the structure of Fe-N4,accompanied with the addition of appropriate Fe,and the number of active sites increases without the occurrence of agglomeration ***,it is speculated that Fe plays an important role in stabilizing N as well as constituting active sites in the second pyrolyzing process.
Shape-controlled Pt-Ni alloys usually offer an exceptional electrocatalytic activity toward the oxygen reduction reaction(ORR)of polymer electrolyte membrane fuel ceils(PEMFCs),whose tricks lie in welldesigned structu...
详细信息
Shape-controlled Pt-Ni alloys usually offer an exceptional electrocatalytic activity toward the oxygen reduction reaction(ORR)of polymer electrolyte membrane fuel ceils(PEMFCs),whose tricks lie in welldesigned structures and surface *** this paper,a novel synthesis of truncated octahedral PtNi_(3.5) alloy catalysts that consist of homogeneous Pt-Ni alloy cores enclosed by NiO-Pt double shells through thermally annealing defective heterogeneous PtNi35 alloys is *** tracking the evolution of both compositions and morphologies,the outward segregation of both PtOv and NiO are first observed in Pt-Ni *** is speculated that the diffusion of low-coordination atoms results in the formation of an energetically favorable truncated octahedron while the outward segregation of oxides leads to the formation of NiO-Pt double *** is very attractive that after gently removing the NiO outer shell,the dealloyed truncated octahedral core-shell structure demonstrates a greatly enhanced ORR *** asobtained truncated octahedral Pt_(2.1)Ni core-shell alloy presents a 3.4-folds mass-specific activity of that for unannealed sample,and its activity preserves 45.4%after 30000 potential cycles of accelerated degradation test(ADT).The peak power density of the dealloyed truncated octahedral Pt2jNi core-shell alloy catalyst based membrane electrolyte assembly(MEA)reaches 679.8 mW/cm^(2),increased by 138.4 mW/cm^(2) relative to that based on commercial Pt/C.
Thermal management is considered a critical issue in proton exchange membrane fuel cells(PEMFCs),since it not only influences the cell performance but also impacts PEMFC’s reliability and *** the ever-increasing powe...
详细信息
Thermal management is considered a critical issue in proton exchange membrane fuel cells(PEMFCs),since it not only influences the cell performance but also impacts PEMFC’s reliability and *** the ever-increasing power density of PEMFC,traditional cooling approaches including air cooling and water cooling become difficult to meet the demand for highpower heat ***,phase-change cooling is proposed for fuel cell application in this work,and the potential advantages are discussed and demonstrated via a mathematical model incorporating phase-change heat *** thermal management performance is evaluated by temperature uniformity,maximum temperature difference,and the cooling capacity to compare the difference between phase-change cooling and traditional methods,which demonstrates that phase-change cooling owns a greatly improved thermal management *** addition,a simple method to broaden the operating temperature of phase-change cooling based on one certain coolant is offered,which is pressurizing in the coolant channel to regulate the boiling temperature that could further improve the application feasibility of phase-change cooling strategy in fuel cells.
An environment-friendly,water-soluble,and cellulose based binder(lithium carboxymethyl cellulose,CMC-Li)was successfully synthesized by using Li+to replace Na+in the commercial sodium carboxymethyl cellulose(CMC-Na).L...
详细信息
An environment-friendly,water-soluble,and cellulose based binder(lithium carboxymethyl cellulose,CMC-Li)was successfully synthesized by using Li+to replace Na+in the commercial sodium carboxymethyl cellulose(CMC-Na).Li-O2 batteries based on the CMC-Li binder present enhanced discharge specific capacities(11151 mAh/g at 100 mA/g)and a superior cycling stability(100 cycles at 200 mA/g)compared with those based on the CMC-Na *** enhanced performance may originate from the electrochemical stability of the CMC-Li binder and the ion-conductive nature of CMC-Li,which promotes the diffusion of Li+in the cathode and consequently retards the increase of charge transfer resistance of the cathode during *** results show that the water-soluble CMC-Li binder can be a green substitute for poly(vinylidene fluoride)(PVDF)binder based on organic solvent in the lithium oxygen batteries(LOBs).
Undoubtedly, it is imperative to figure out two stubborn issues concerning low electronic conductivity and sluggish lithium ion diffusion to promote the practical application of Li2FeSiO4 materials in lithium-ion batt...
详细信息
Undoubtedly, it is imperative to figure out two stubborn issues concerning low electronic conductivity and sluggish lithium ion diffusion to promote the practical application of Li2FeSiO4 materials in lithium-ion battery (LIB) cathode. Herein, we report an innovative and simple strategy that combines a hydrothermal process with subsequent annealing to synthesize highly uniform Li2FeSiO/C hollow nanospheres. During the hydrothermal process, polystyrenen anospheres are employed not only as the template but also, more tactfully, as carb on source to form amorphous carbon layers, which will function to enhance the electronic conductivity and restrict particle aggregations. The use of the LIB Li2FeSiO4/C hollow nano spheres as a LIB cathode delivers a desired stable capacity at each rate stage, and eve n at a high rate of 10 C, the hollow nano sphere cathode can prese nt a specific discharge capacity as high as 50.5 mAh·g^-1. After 100 cycles, the capacity rete ntions at 1 and 10 C remain as high as 93% and 72%, respectively. The superior electrochemical performance is believed to be related to special architectures of the Li2FeSiO4/C hollow nano sphere cathode.
Un doubtedly,there remai ns an urge nt prerequisite to achieve sign ifica nt adva nces in both the specific capacity and cyclability of Li-O2 batteries for their practical *** this work,a series of unique three-dimens...
详细信息
Un doubtedly,there remai ns an urge nt prerequisite to achieve sign ifica nt adva nces in both the specific capacity and cyclability of Li-O2 batteries for their practical *** this work,a series of unique three-dimensional(3D)α-MnO2/MWCNTs hybrids are successfully prepared using a facile lyophilization method and investigated as the cathode of Li-O2 ***,cross-1 inkedα-MnO2/MWCNTs nano composites are first syn thesized via a modified chemical *** dem on strate that MnO2 nano rods in the nano composites have a length of 100-400 nm and a diameter ranging from 5 to 10 nm,and more attractively,the as-lyophilized 3D MnO2/MWCNTs hybrids is uniquely constructed with large amounts of interconnected macroporous *** U-O2 battery with the 3D macroporous hybrid cathode that has a mass percentage of 50%ofα-MnO2 delivers a high discharge specific capacity of 8,643 mAh·g^-1 at 100 mA·g^-1,and main tains over 90 cycles before the discharge voltage drops to 2.0 V un der a controlled specific capacity of 1,000 mAh·g^-*** is observed that when being recharged,the product of toroidal Li2O2 particles disappears and electrode surfaces are well recovered,thus confirming a good *** excellent performanee of Li-O2 battery with the 3Dα-MnO2/MWCNTs macroporous hybrid cathode is ascribed to a syn ergistic com bination betwee n the unique macroporous architecture and highly efficient bi-fun ctionalα-MnO2/MWCNTs electrocatalyst.
It is highly desired but challenging to develop platinum group metal-free electrocatalysts for oxygen reduction reaction(ORR), which can promote the commercialization of fuel cell technology. To achieve this target, w...
详细信息
It is highly desired but challenging to develop platinum group metal-free electrocatalysts for oxygen reduction reaction(ORR), which can promote the commercialization of fuel cell technology. To achieve this target, we report a one-step doping method to prepare S-doped Fe–N–C catalysts using zeolite imidazole framework(ZIF-8)and iron(III) thiocyanate(Fe(SCN)3) as precursor. Different from conventional doping approach, i.e. physical mixing, Fe(SCN)3is in-situ added during ZIF-8 formation which would encapsulate Fe(SCN)3molecules inside ZIF-8 to avoid structure destruction and create potential replacement of Zn ions by Fe ions to form uniform Fe–N4 complexes. As a result, the prepared S-doped Fe–N–C catalysts own large specific surface areas with a maximum value of 1326 m2g-1and a dual-scale porous structure that benefits mass transport. Significantly, the composition-optimized catalyst exhibits superior ORR activity in both 0.1 M HCl O4electrolyte and 0.1 M KOH electrolyte, in which the half-wave potential reaches 0.81 V and 0.92 V(vs. RHE), respectively. Remarkable stability is also attained, which loses 2 m V only after 10000 potential cycles in O2-saturated 0.1 M HCl O4and remains almost constant in O2-saturated 0.1 M KOH, surpassing commercial Pt/C catalyst in both acidic and alkaline medium.
In this study,we investigated the hydrogen evolution reaction(HER)on the(101)facet of pristine and W-doped CoP using the density functional *** types of Co atoms are identified on the catalyst surface:the Co atoms tha...
详细信息
In this study,we investigated the hydrogen evolution reaction(HER)on the(101)facet of pristine and W-doped CoP using the density functional *** types of Co atoms are identified on the catalyst surface:the Co atoms that present the higher d band center are marked as valid sites,whereas the others are marked as invalid sites owing to their weaker H adsorption *** is further revealed that W-doping can decrease the d band center of the surface Co atoms,which is beneficial for the HER;however the exposure to W weakens the desorption of *** address the strong adsorption effect of W,the doping sites and dopant content are analyzed,and the results indicate that 8.4 wt%W doping at the invalid surface Co sites is preferred;moreover,the optimal W content increases to 16.8 wt%when W is inserted into the *** effect of W doping is weakened when the doping site is far away from the surface.
In this work,highly monodispersed Pt-Ni alloy nanoparticles were directly deposited on carbon substrate through a facile electrodeposition strategy in the solvent system of N,N-dimethylformamide(DMF).A series of carbo...
详细信息
In this work,highly monodispersed Pt-Ni alloy nanoparticles were directly deposited on carbon substrate through a facile electrodeposition strategy in the solvent system of N,N-dimethylformamide(DMF).A series of carbon supported Pt-Ni alloy electrocatalysts were synthesized under different applied electrode *** all as-obtained samples,the Pt-Ni/C electrocatalyst deposited at-1.73 V exhibits the optimal specific activity up to 1.850 mA cm^(-2)at 0.9 V ***,which is 6.85 times higher than that of the commercial Pt/*** physiochemical characterizations and computational evaluations via density functional theory were conducted to unveil the nucleation and growth mechanism of PtNi alloy *** to the aqueous solution,DMF solvent molecule must not be neglected in avoiding particle agglomeration and synthesis of monodispersed *** the alloy co-deposition process,Ni sites produced through the reduction of Ni(Ⅱ)precursor not only facilitates Pt-Ni alloy crystal nucleation but also in favor of further Pt reduction on the Ni-inserted Pt *** for the deposition potential,it adjusts the final particle *** work provides a hopeful extended Pt-based catalyst layer production strategy for proton exchange membrane fuel cells and a new idea for the nucleation and growth mechanism exploration for electrodeposited Pt alloy.
暂无评论