The development of metal‐N‐C materials as efficient non‐precious metal (NPM) catalysts for catalysing the oxygen reduction reaction (ORR) as alternatives to platinum is important for the practical ...use of proton exchange membrane fuel cells (PEMFCs). However, metal‐N‐C materials have high structural heterogeneity. As a result of their high‐temperature synthesis they often consist of metal‐Nx sites and graphene‐encapsulated metal nanoparticles. Thus it is hard to identify the active structure of metal‐N‐C catalysts. Herein, we report a low‐temperature NH4Cl‐treatment to etch out graphene‐encapsulated nanoparticles from metal‐N‐C catalysts without destruction of co‐existing atomically dispersed metal‐Nx sites. Catalytic activity is much enhanced by this selective removal of metallic nanoparticles. Accordingly, we can confirm the spectator role of graphene‐encapsulated nanoparticles and the pivotal role of metal‐Nx sites in the metal‐N‐C materials for ORR in the acidic medium.
ORR inspiring: With a low‐temperature NH4Cl treatment graphene‐encapsulated nanoparticles (NPs) are etched out of metal‐N‐C catalysts. Removing these metallic NPs greatly enhances the catalytic oxygen reduction reaction (ORR) activity allowing the real catalytic centres to be identified.
Metal-support interaction is of great significance for catalysis as it can induce charge transfer between metal and support, tame electronic structure of supported metals, impact adsorption energy of ...reaction intermediates, and eventually change the catalytic performance. Here, we report the metal size-dependent charge transfer reversal, that is, electrons transfer from platinum single atoms to sulfur-doped carbons and the carbon supports conversely donate electrons to Pt when their size is expanded to ~1.5 nm cluster. The electron-enriched Pt nanoclusters are far more active than electron-deficient Pt single atoms for catalyzing hydrogen evolution reaction, exhibiting only 11 mV overpotential at 10 mA cm
and a high mass activity of 26.1 A mg
at 20 mV, which is 38 times greater than that of commercial Pt/C. Our work manifests that the manipulation of metal size-dependent charge transfer between metal and support opens new avenues for developing high-active catalysts.
Abstract
Metal single-atom catalysts (M-SACs) have emerged as an attractive concept for promoting heterogeneous reactions, but the synthesis of high-loading M-SACs remains a challenge. Here, we ...report a multilayer stabilization strategy for constructing M-SACs in nitrogen-, sulfur- and fluorine-co-doped graphitized carbons (M = Fe, Co, Ru, Ir and Pt). Metal precursors are embedded into perfluorotetradecanoic acid multilayers and are further coated with polypyrrole prior to pyrolysis. Aggregation of the metals is thus efficiently inhibited to achieve M-SACs with a high metal loading (~16 wt%). Fe-SAC serves as an efficient oxygen reduction catalyst with half-wave potentials of 0.91 and 0.82 V (versus reversible hydrogen electrode) in alkaline and acid solutions, respectively. Moreover, as an air electrode in zinc–air batteries, Fe-SAC demonstrates a large peak power density of 247.7 mW cm
−2
and superior long-term stability
.
Our versatile method paves an effective way to develop high-loading M-SACs for various applications.
Atomically ordered intermetallic nanoparticles are promising for catalytic applications but are difficult to produce because the high-temperature annealing required for atom ordering inevitably ...accelerates metal sintering that leads to larger crystallites. We prepared platinum intermetallics with an average particle size of <5 nanometers on porous sulfur-doped carbon supports, on which the strong interaction between platinum and sulfur suppresses metal sintering up to 1000°C. We synthesized intermetallic libraries of small nanoparticles consisting of 46 combinations of platinum with 16 other metal elements and used them to study the dependence of electrocatalytic oxygen-reduction reaction activity on alloy composition and platinum skin strain. The intermetallic libraries are highly mass efficient in proton-exchange-membrane fuel cells and could achieve high activities of 1.3 to 1.8 amperes per milligram of platinum at 0.9 volts.
Metal‐containing nanoparticles (M‐NPs) in metal/nitrogen‐doped carbon (M‐N‐C) catalysts have been considered hostile to the acidic oxygen reduction reaction (ORR). The relation between M‐NPs and the ...active sites of metal coordinated with nitrogen (MNx) is hard to establish in acid medium owing to the poor stability of M‐NPs. Herein, we develop a strategy to successfully construct a new FeCo‐N‐C catalyst containing highly active M‐NPs and MN4 composite sites (M/FeCo‐SAs‐N‐C). Enhanced catalytic activity and stability of M/FeCo‐SAs‐N‐C is shown experimentally. Calculations reveal that there is a strong interaction between M‐NPs and FeN4 sites, which can favor ORR by activating the O−O bond, thus facilitating a direct 4 e− process. Those findings firstly shed light on the highly active M‐NPs and FeN4 composite sites for catalyzing acid oxygen reduction reaction, and the relevant reaction mechanism is suggested.
Highly active metal‐containing nanoparticles and FeN4 composite sites have been constructed. Experiment and calculation results reveal the enormous potential for activating the O−O bond and promoting the direct 4 e− dissociation pathway in the acidic oxygen reduction reaction (ORR), which could fundamentally improve ORR activity and inhibit the formation of reactive oxygen species.
Heterostructures exhibit considerable potential in the field of energy conversion due to their excellent interfacial charge states in tuning the electronic properties of different components to ...promote catalytic activity. However, the rational preparation of heterostructures with highly active heterosurfaces remains a challenge because of the difficulty in component tuning, morphology control, and active site determination. Herein, a novel heterostructure based on a combination of RuMo nanoalloys and hexagonal N‐doped carbon nanosheets is designed and synthesized. In this protocol, metal‐containing anions and layered double hydroxides are employed to control the components and morphology of heterostructures, respectively. Accordingly, the as‐made RuMo‐nanoalloys‐embedded hexagonal porous carbon nanosheets are promising for the hydrogen evolution reaction (HER), resulting in an extremely small overpotential (18 mV), an ultralow Tafel slope (25 mV dec−1), and a high turnover frequency (3.57 H2 s−1) in alkaline media, outperforming current Ru‐based electrocatalysts. First‐principle calculations based on typical 2D N‐doped carbon/RuMo nanoalloys heterostructures demonstrate that introducing N and Mo atoms into C and Ru lattices, respectively, triggers electron accumulation/depletion regions at the heterosurface and consequently reduces the energy barrier for the HER. This work presents a convenient method for rational fabrication of carbon–metal heterostructures for highly efficient electrocatalysis.
A novel heterostructure based on uniform RuMo nanoalloys and hexagonal N‐doped carbon nanosheets is prepared through a combination of hard template and anion‐exchange methods. The obtained material exhibits excellent electrocatalytic activity for the hydrogen evolution reaction. Theoretical calculation confirms that the heterosurfaces play a crucial role in accelerating the hydrogen evolution activity.
Platinum‐based atomically ordered alloys (i.e., intermetallic compounds) have distinct advantages over disordered solid solution counterparts in boosting the cathodic oxygen‐reduction reaction (ORR) ...in proton‐exchange‐membrane fuel cells. Nevertheless, the pivotal role of ordering degree of intermetallic catalysts in promoting ORR performance has been ignored heavily so far, probably owing to the lack of synthetic routes for controlling the ordering degree, especially for preparing highly ordered intermetallic catalysts. Herein, a family of intermetallic PtFe catalysts with similar particle size of 3–4 nm but varied ordering degree in a wide range of 10–70% are prepared. After constructing the PtFe/Pt core/shell structure with around 3 Pt‐layer skin, a positive correlation between the ordering degree of the intermetallic catalysts and their ORR activity and durability is identified. Notably, the highly ordered PtFe/Pt catalyst exhibits a high mass activity of 0.92 A mgPt−1 at 0.9 ViR‐corrected as cathode catalyst in H2–O2 fuel cell, with only 24% loss after accelerated durability tests. The ordering degree‐dependent performance can be ascribed to the compressive strain effect induced by the intermetallic PtFe core with smaller lattice parameters, and the more thermodynamically stable intermetallic structure compared to disordered alloys.
A strong and positive correlation between the ordering degree of the PtFe/Pt catalysts with their oxygen reduction reaction activity and durability is identified, which can be ascribed to the compressive strain effects and the more thermodynamically stable intermetallic structures compared to disordered alloys.
The development of low‐cost catalysts containing earth‐abundant elements as alternatives to Pt‐based catalysts for the oxygen reduction reaction (ORR) is crucial for the large‐scale commercial ...application of proton exchange membrane fuel cells (PEMFCs). Nonprecious metal–nitrogen–carbon (M‐N‐C) materials represent the most promising candidates to replace Pt‐based catalysts for PEMFCs applications. However, the high‐temperature pyrolysis process for the preparation of M‐N‐C catalysts frequently leads to high structural heterogeneity, that is, the coexistence of various metal‐containing sites and N‐doped carbon structures. Unfortunately, this impedes the identification of the predominant catalytic active structure, and thus, the further development of highly efficient M‐N‐C catalysts for the ORR. This Minireview, after a brief introduction to the development of M‐N‐C ORR catalysts, focuses on the commonly accepted views of predominant catalytic active structures in M‐N‐C catalysts, including atomically dispersed metal–Nx sites, metal nanoparticles encapsulated with nitrogen‐doped carbon structures, synergistic action between metal–Nx sites and encapsulated metal nanoparticles, and metal‐free nitrogen‐doped carbon structures.
Elucidating active sites: As one of the most promising candidates to replace noble metal catalysts for fuel‐cell applications, the active structure in nonprecious metal–nitrogen–carbon (M‐N‐C)‐based materials is still a matter of controversy owing to the high structural heterogeneity. This Minireview provides a summary of commonly accepted views of predominant catalytic active structures in M‐N‐C catalysts.
As a major class of noncoding RNAs, long noncoding RNAs (lncRNAs) have been implicated in various critical biological processes. Accumulating researches have linked dysregulations and mutations of ...lncRNAs to a variety of human disorders and diseases. However, to date, only a few human lncRNAs have been associated with diseases. Therefore, it is very important to develop a computational method to globally predict potential associated diseases for human lncRNAs. In this paper, we developed a computational framework to accomplish this by combining human lncRNA expression profiles, gene expression profiles, and human disease-associated gene data. Applying this framework to available human long intergenic noncoding RNAs (lincRNAs) expression data, we showed that the framework has reliable accuracy. As a result, for non-tissue-specific lincRNAs, the AUC of our algorithm is 0.7645, and the prediction accuracy is about 89%. This study will be helpful for identifying novel lncRNAs for human diseases, which will help in understanding the roles of lncRNAs in human diseases and facilitate treatment. The corresponding codes for our method and the predicted results are all available at http://asdcd.amss.ac.cn/MingXiLiu/lncRNA-disease.html.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Iridium-based electrocatalysts remain the only practical anode catalysts for proton exchange membrane (PEM) water electrolysis, due to their excellent stability under acidic oxygen evolution reaction ...(OER), but are greatly limited by their high cost and low reserves. Here, we report a nickel-stabilized, ruthenium dioxide (Ni-RuO
) catalyst, a promising alternative to iridium, with high activity and durability in acidic OER for PEM water electrolysis. While pristine RuO
showed poor acidic OER stability and degraded within a short period of continuous operation, the incorporation of Ni greatly stabilized the RuO
lattice and extended its durability by more than one order of magnitude. When applied to the anode of a PEM water electrolyser, our Ni-RuO
catalyst demonstrated >1,000 h stability under a water-splitting current of 200 mA cm
, suggesting potential for practical applications. Density functional theory studies, coupled with operando differential electrochemical mass spectroscopy analysis, confirmed the adsorbate-evolving mechanism on Ni-RuO
, as well as the critical role of Ni dopants in stabilization of surface Ru and subsurface oxygen for improved OER durability.
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