Transition metal–nitrogen–carbon (TM–N–C) catalysts have been intensely investigated to tackle the sluggish oxygen reduction reactions (ORRs), but insufficient accessibility of the active sites ...limits their performance. Here, by using solid ZIF‐L nanorods as self‐sacrifice templates, a ZIF‐phase‐transition strategy is developed to fabricate ZIF‐8 hollow nanorods with open cavities, which can be subsequently converted to atomically dispersed Fe‐N‐C hollow nanorods (denoted as Fe1–N–C HNRs) through rational carbonization and following fixation of iron atoms. The microstructure observation and X‐ray absorption fine structure analysis confirm abundant Fe–N4 active sites are evenly distributed in the carbon skeleton. Thanks to the highly accessible Fe‐N4 active sites provided by the highly porous and open carbon hollow architecture, the Fe1‐N‐C HNRs exhibit superior ORR activity and stability in alkaline and acidic electrolytes with very positive half‐wave potentials of 0.91 and 0.8 V versus RHE, respectively, both of which surpass those of commercial Pt/C. Remarkably, the dynamic current density (JK) of Fe1‐N‐C HNRs at 0.85 V versus RHE in alkaline media delivers a record value of 148 mA cm−2, 21 times higher than that of Pt/C. The assembled Zn‐air battery using Fe1–N–C HNRs as cathode catalyst exhibits a high peak power density of 208 mW cm−2.
By using solid ZIF‐L nanorods as self‐sacrifice templates, a unique ZIF‐phase‐transition strategy is developed to fabricate atomically dispersed Fe–N–C hollow nanorods (Fe1–N–C HNRs) with highly open architecture and abundant exposed Fe–N4 active sites, which can be utilized as efficient oxygen reduction reaction electrocatalysts in both alkaline and acid conditions.
It is challenging yet promising to design highly accessible N‐doped carbon skeletons to fully expose the active sites inside single‐atom catalysts. Herein, mesoporous N‐doped carbon hollow spheres ...with regulatable through‐pore size can be formulated by a simple sequential synthesis procedure, in which the condensed SiO2 is acted as removable dual‐templates to produce both hollow interiors and through‐pores, meanwhile, the co‐condensed polydopamine shell is served as N‐doped carbon precursor. After that, Fe─N─C hollow spheres (HSs) with highly accessible active sites can be obtained after rationally implanting Fe single‐atoms. Microstructural analysis and X‐ray absorption fine structure analysis reveal that high‐density Fe─N4 active sites together with tiny Fe clusters are uniformly distributed on the mesoporous carbon skeleton with abundant through‐pores. Benefitted from the highly accessible Fe─N4 active sites arising from the unique through‐pore architecture, the Fe─N─C HSs demonstrate excellent oxygen reduction reaction (ORR) performance in alkaline media with a half‐wave potential up to 0.90 V versus RHE and remarkable stability, both exceeding the commercial Pt/C. When employing Fe─N─C HSs as the air‐cathode catalysts, the assembled Zn–air batteries deliver a high peak power density of 204 mW cm−2 and stable discharging voltage plateau over 140 h.
Using two types of orthosilicates with different hydrolysis rates as dual‐silica sources and dopamine as the N‐doped carbon sources, a sequential synthesis procedure referred to the classic Stöber method is developed to fabricate N‐doped carbon hollow spheres with abundant unusual through‐pores. The formed N‐doped carbon hollow spheres can act as a favorable host to isolate Fe single‐atoms.
Single‐atom Fe–N–C (Fe1–N–C) materials represent the benchmarked electrocatalysts for oxygen reduction reaction (ORR). However, single Fe atoms in the carbon skeletons cannot be fully utilized due to ...the mass transfer limitation, severely restricting their intrinsic ORR properties. Herein, a self‐sacrificing template strategy is developed to fabricate ultrathin nanosheets assembled Fe1–N–C hollow microspheres (denoted as Fe1/N‐HCMs) by rational carbonization of Fe3+ chelating polydopamine coated melamine cyanuric acid complex. The shell of Fe1/N‐HCMs is constructed by ultrathin nanosheets with thickness of only 2 nm, which is supposed to be an ideal platform to isolate and fully expose single metal atoms. Benefiting from unique hierarchical hollow architecture with highly open porous structure, 2 nm‐thick ultrathin nanosheet subunits and abundant Fe–N4O1 active sites revealed by X‐ray absorption fine structure analysis, the Fe1/N‐HCMs exhibit high ORR performance with a positive half‐wave potential of 0.88 V versus the reversible hydrogen electrode and robust stability. When served as air‐cathode catalysts with ultralow loading mass of 0.25 mg cm−2, Fe1/N‐HCMs based Zn–air batteries present a maximum power density of 187 mW cm−2 and discharge specific capacity of 806 mA h gZn−1 in primary Zn–air batteries, all exceeding those of commercial Pt/C.
A self‐sacrificing template strategy is developed to fabricate 2 nm‐thick nanosheets assembled Fe1–N–C hollow microspheres (Fe1/N‐HCMs) with highly open porous architecture, which is supposed to fully expose the catalytic active sites to boost the oxygen reduction reaction. Unlike the general Fe–N4 configuration in most reported Fe1–N–C catalysts, the active sites in Fe1/N‐HCMs have been identified as Fe–N4O1 configuration.
The low energy efficiency and limited cycling life of rechargeable Zn–air batteries (ZABs) arising from the sluggish oxygen reduction/evolution reactions (ORR/OERs) severely hinder their commercial ...deployment. Herein, a zeolitic imidazolate framework (ZIF)‐derived strategy associated with subsequent thermal fixing treatment is proposed to fabricate dual‐atom CoFe─N─C nanorods (Co1Fe1─N─C NRs) containing atomically dispersed bimetallic Co/Fe sites, which can promote the energy efficiency and cyclability of ZABs simultaneously by introducing the low‐potential oxidation redox reactions. Compared to the mono‐metallic nanorods, Co1Fe1─N─C NRs exhibit remarkable ORR performance including a positive half‐wave potential of 0.933 V versus reversible hydrogen electrode (RHE) in alkaline electrolyte. Surprisingly, after introducing the potassium iodide (KI) additive, the oxidation overpotential of Co1Fe1─N─C NRs to reach 10 mA cm−2 can be significantly reduced by 395 mV compared to the conventional destructive OER. Theoretical calculations show that the markedly decreased overpotential of iodide oxidation can be ascribed to the synergistic effects of neighboring Co─Fe diatomic sites as the unique adsorption sites. Overall, aqueous ZABs assembled with Co1Fe1─N─C NRs and KI as the air–cathode catalyst and electrolyte additive, respectively, can deliver a low charging voltage of 1.76 V and ultralong cycling stability of over 230 h with a high energy efficiency of ≈68%.
A zeolitic imidazolate framework (ZIF)derived strategy associated with subsequent thermal fixing treatment is proposed to fabricate dual‐atom CoFe─N─C nanorods containing atomically dispersed bimetallic Co/Fe sites, which can be used as bifunctional air–cathode catalysts to boost the energy efficiency and cyclability of Zn–air batteries simultaneously by introducing low‐potential oxidation redox reactions.
We propose a robust multispectral transparent plasmonic structure and calculate its transparency response by using the three-dimensional finite-difference time-domain (FDTD) method. The proposed ...structure is composed of a continuous ultrathin metal film sandwiched by double two-dimensional (2D) hexagonal non-close-packed metal-dielectric multilayer core-shell nanoparticle arrays. The top and bottom plasmonic arrays in such a structure, respectively, act as the light input and output couplers to carry out the efficient trapping and release of light. Near-perfect multispectral optical transparency in the visible and near-infrared regions is achieved theoretically. The calculated electric field distribution patterns show that the near-perfect multispectral optical transparency mainly originates from the excitation and hybridization of shell and core plasmon modes, strong near-field coupling of dipole plasmon modes between adjacent nanoparticles as well as the excitation of surface plasmon waves of the metal film. The robust transparency bands can be efficiently tuned in a large range by varying the structural parameters and the surrounding dielectric environment. The proposed structure also shows additional merits such as a deep sub-wavelength size and fully retained electrical and mechanical properties of the natural metal. These features might provide promising applications in highly integrated optoelectronic devices including plasmonic filters, nanoscale multiplexers, and non-linear optics.
The robust multispectral transparency in a continuous ultrathin metal film is demonstrated
via
the hybridization of multiple near-field plasmon coupling in this system.
Single‐atom Fe‐N‐C (denoted as Fe1‐N‐C) catalysts exhibit inadequate bifunctional activities to conquer the sluggish oxygen reduction and evolution reaction (ORR/OER), hindering their practical ...applications in rechargeable Zn‐air batteries (ZABs). Here, by employing Fe1‐N‐C hollow nanorods as ORR‐active support, OER‐active NiFe‐layered double hydroxide (NiFe‐LDH) nanodots are evenly decorated through a spatially confined process to form NiFe‐LDH/Fe1‐N‐C heterostructure hollow nanorods with abundant accessible catalytic sites. The NiFe‐LDH/Fe1‐N‐C heterostructure not only enhances the ORR activity of pristine Fe1‐N‐C but also realizes efficient bifunctional ORR/OER activity in one monolithic catalyst. Theoretical calculations reveal that introducing NiFe‐LDH nanodots results in donation of electrons to the Fe1‐N‐C matrix and thus lowers the Fe‐d band center of the Fe‐N4 sites, dramatically narrowing the energy barriers of the ORR rate‐limiting steps. As a result, NiFe‐LDH/Fe1‐N‐C nanorods deliver remarkable ORR activity with a half‐wave potential of 0.90 V versus reversible hydrogen electrode, surpassing bare Fe1‐N‐C and commercial Pt/C. Impressively, the integrated NiFe‐LDH/Fe1‐N‐C catalysts show outstanding bifunctional performance with a small overpotential gap of only 0.65 V. The liquid‐state ZABs with NiFe‐LDH/Fe1‐N‐C as an air‐cathode catalyst deliver a peak power density of 205 mW cm−2 and long‐term cycling stability of up to 400 h.
Oxygen evolution reaction (OER)‐active NiFe‐layered double hydroxide (LDH) nanodots are evenly decorated on the oxygen reduction reaction (ORR)‐active Fe1‐N‐C hollow nanorods to realize bifunctional ORR/OER activity in one monolithic catalyst with a small overpotential gap of only 0.65 V. NiFe‐LDH regulates the electronic structures of Fe1‐N‐C by transferring electrons to the Fe‐N4‐active sites and thus significantly reduces the energy barrier of the rate‐determining step during the ORR.
Development of bifunctional oxygen electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reactions (OER) is urgently needed for advanced energy storage and conversion devices ...including rechargeable Zn-air batteries. Herein, we put forward the design and synthesis of nitrogen-doped carbon nanotubes binding Co-N-C elongated hexagonal nanoplates (denoted as Co-N-C@NCNTs) through a metastable bimetallic ZnCo-ZIF-L topochemical phase conversion and subsequent pyrolysis strategy. The highly open and conductive architectures with an elongated shape of a carbon nanoplate substrate can not only effectively prevent the agglomeration of catalytically active sites comprised of both Co nanoparticles and atomic Co-N
x
species, but also accelerate the electron and ion transport during the catalytic process to improve the mass transfer efficiency, resulting in enhanced electrocatalytic performance in both electrocatalytic activity and stability. As expected, the Co-N-C@NCNTs showed excellent bifunctional ORR/OER performance with an overpotential gap of 0.748 V and satisfactory stability. Using Co-N-C@NCNTs as air-cathode catalysts for rechargeable Zn-air batteries, the assembled cells exhibit a remarkable peak power density of 237.8 mW cm
−2
and long-term cycling stability of up to 130 h.
A metastable bimetallic ZnCo-ZIF-L topochemical phase conversion and subsequent pyrolysis strategy was developed to fabricate Co-N-C@NCNTs, which exhibit excellent ORR/OER performance with an overpotential gap of 0.748 V.
Abstract
Single‐atom Fe‐N‐C (denoted as Fe
1
‐N‐C) catalysts exhibit inadequate bifunctional activities to conquer the sluggish oxygen reduction and evolution reaction (ORR/OER), hindering their ...practical applications in rechargeable Zn‐air batteries (ZABs). Here, by employing Fe
1
‐N‐C hollow nanorods as ORR‐active support, OER‐active NiFe‐layered double hydroxide (NiFe‐LDH) nanodots are evenly decorated through a spatially confined process to form NiFe‐LDH/Fe
1
‐N‐C heterostructure hollow nanorods with abundant accessible catalytic sites. The NiFe‐LDH/Fe
1
‐N‐C heterostructure not only enhances the ORR activity of pristine Fe
1
‐N‐C but also realizes efficient bifunctional ORR/OER activity in one monolithic catalyst. Theoretical calculations reveal that introducing NiFe‐LDH nanodots results in donation of electrons to the Fe
1
‐N‐C matrix and thus lowers the Fe‐
d
band center of the Fe‐N
4
sites, dramatically narrowing the energy barriers of the ORR rate‐limiting steps. As a result, NiFe‐LDH/Fe
1
‐N‐C nanorods deliver remarkable ORR activity with a half‐wave potential of 0.90 V versus reversible hydrogen electrode, surpassing bare Fe
1
‐N‐C and commercial Pt/C. Impressively, the integrated NiFe‐LDH/Fe
1
‐N‐C catalysts show outstanding bifunctional performance with a small overpotential gap of only 0.65 V. The liquid‐state ZABs with NiFe‐LDH/Fe
1
‐N‐C as an air‐cathode catalyst deliver a peak power density of 205 mW cm
−2
and long‐term cycling stability of up to 400 h.
Objectives
To evaluate the efficacy and safety of adalimumab (ADA) combined with Tripterygium wilfordii Hook F (TwHF) in the treatment of methotrexate (MTX)‐inadequate response patients with ...rheumatoid arthritis (RA).
Methods
In this multicenter, open‐label, randomized controlled clinical trial, 64 RA patients with inadequate response to MTX were 1:1 randomly assigned into treatment or control groups. The treatment group was treated with ADA in combination with TwHF, and the control group was treated with ADA in combination with MTX for 24 weeks. The primary endpoint was the percentage of patients having low disease activity (2.6 ≤ DAS28‐ESR < 3.2) and remission rates (DAS28‐ESR < 2.6) at week 24.
Results
In total, 53 of the 64 patients (82.8%) completed this 24‐week clinical trial. By intent‐to‐treat (ITT) analysis, a comparable outcome was observed between the two groups. The percentage of patients achieving low disease activity in the treatment group and control group were 43.8% and 46.9% (95% CI, 21.28 to 27.48, p = .802). Percentage of patients achieving low disease activity rates were respectively 28.1% and 31.3% in the treatment group and control group (95% CI, 19.18 to 25.58, p = .784). In per‐protocol (PP) analysis, the results were consistent with the ITT model. The incidence of adverse events was comparable between the two groups.
Conclusions
There were no significant differences in efficacy and safety between ADA combined with TwHF versus ADA combined with MTX in the treatment of RA. TwHF might be an alternative treatment for RA patients who are intolerant to MTX.
