Boron doped graphene wrapped silver nanowires as an efficient electrocatalyst for molecular oxygen reduction (original) (raw)
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Metal nanoclusters exhibit unusually high catalytic activity toward oxygen reduction reaction (ORR) due to their small size and unique electronic structures. However, controllable synthesis of stable metal nanoclusters is a challenge, and the durability of metal clusters suffers from the deficiency of dissolution, aggregation, and sintering during catalysis reactions. Herein, silver nanoclusters (AgNCs) (diameter < 2 nm) were controllably electrochemically reduced on nitrogen-doped graphene (NG) using effective single-stranded oligonucleotide sequences (ssDNA) as the performed template in absence of any other reluctant. The ssDNA is significant for providing AgNCs with growth template and anchoring the cluster on graphene surface. The strong interaction between the AgNCs, ssDNA and NG renders the as-synthesized AgNCs/NG composite with high-performance onset potential, half-wave potential and mass activity for ORR approaching to commercial Pt/C catalyst, and remarkably superior ORR performance than NG and Ag nanoparticle/NG. Importantly, the AgNCs/NG composite shows excellent methanol tolerance and accelerated electrochemical stability (8000 cycles), which is vital in high performance fuel cells, batteries and nanodevices.
Electroreduction of oxygen on nitrogen-doped graphene oxide supported silver nanoparticles
Journal of Electroanalytical Chemistry, 2017
Nitrogen-doped graphene oxide supported silver nanoparticles (Ag/NGO) have been synthesised using three different methods. The prepared catalysts were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and electrochemically tested for oxygen reduction reaction (ORR) in alkaline solution. The Ag/NGO catalysts prepared by borohydride reduction showed the least degree of nanoparticle agglomeration and the material which was prepared using ascorbic acid yielded the biggest Ag particles. XPS revealed that the nitrogen to carbon atomic ratio was about 0.07 and EDS mapping showed that it was uniformly distributed over the graphene. The ORR on all the Ag/NGO catalysts
Nanomaterials
Copper-silver and cobalt-silver alloy nanoparticles deposited on reduced graphene oxide (CuAg/rGO and CoAg/rGO) were synthesized and examined as electrocatalysts for oxygen reduction reaction (ORR) and hydrogen peroxide reduction reaction (HPRR) in alkaline media. Characterization of the prepared samples was done by transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction analysis (XRD), and scanning electron microscopy with integrated energy-dispersive X-ray spectroscopy (SEM-EDS). CuAg/rGO and CoAg/rGO nanoparticles diameter ranged from 0.4 to 9.2 nm. The Ag loading was ca. 40 wt.% for both electrocatalysts, with that for Cu and Co being 35 and 17 wt.%, respectively. CoAg/rGO electrocatalyst showed a Tafel slope of 109 mV dec−1, significantly lower than that for CuAg/rGO (184 mV dec−1), suggesting faster ORR kinetics. Additionally, a higher diffusion current density was obtained for CoAg/rGO (−2.63 mA cm−2) than ...
Chemistry of Materials, 2015
We show that nanoribbons of boron-and nitrogensubstituted graphene can be used as efficient electrocatalysts for the oxygen reduction reaction (ORR). Optimally doped graphene nanoribbons made into three-dimensional porous constructs exhibit the highest onset and half-wave potentials among the reported metal-free catalysts for this reaction and show superior performance compared to commercial Pt/C catalyst. Furthermore, this catalyst possesses high kinetic current density and four-electron transfer pathway with low hydrogen peroxide yield during the reaction. First-principles calculations suggest that such excellent electrocatalytic properties originate from the abundant edges of boron-and nitrogen-codoped graphene nanoribbons, which significantly reduce the energy barriers of the rate-determining steps of the ORR reaction.
Langmuir, 2015
We have developed a potentiostatic double-pulse technique for silver nanoparticle (Ag NP) deposition on graphene (GRn) with superior electronic and ionic conductivity. This approach yielded to a 2D electrocatalysts with a homogenous Ag NP spatial distribution with remarkable performance in the oxygen reduction reaction (ORR). GRn sheets were reproducibly prepared by the electrochemical exfoliation of graphite (GRp) at high yield and purity with a low degree of oxidation. Polystyrene sulfonate added during exfoliation enhanced the stability of the GRn solution by preventing the re-stacking of the graphene sheets and increased its ionic conductivity. The potentiostatic double-pulse technique is generally used to electro-depose Pt nanoparticles and remains challenging for silver metal that exhibits nucleation and growth potentials relatively close to each other. We judiciously exploited this narrow margin of potential Corresponding Author
Solid State Sciences, 2014
Chemically modified graphenes (CMGs) show great promise for various applications owing to the feasibility of their low-cost mass production and good solution processability. Recently, hetero-atomdoped CMGs have been suggested as good candidate materials for electrochemical catalysts in oxygen reduction reaction (ORR). In this study, we synthesized B, N co-doped graphene nano-platelets (BN-rG-O) using a two-step solution process with sequential reaction of graphene oxide with borane tetrahydrofuran and hydrazine monohydrate. In the ORR measured in a basic medium (0.1 M KOH), BN-rG-O exhibits an onset potential of 0.81 V (vs. reversible hydrogen electrode), follows near four electron pathway, and shows excellent stability against methanol poisoning and during durability tests.
Oxygen reduction on silver catalysts electrodeposited on various nanocarbon supports
SN Applied Sciences, 2021
In this work, Ag particles were electrodeposited onto nitrogen-doped graphene oxide, graphene, multi-walled carbon nanotube (MWCNT), and Vulcan carbon XC-72R supports by varying the upper potential limit. The surface morphology of the resulting Ag-based catalysts was examined by scanning electron microscopy. The electrochemical oxygen reduction reaction (ORR) was tested in alkaline media employing the rotating disk electrode method. The variation of the upper potential limit influenced the size of silver nanoparticles and their number density on the substrate surface. All the Ag-based electrocatalysts studied in this work showed remarkable ORR activity in terms of half-wave potentials. The ORR results combined with hydrogen peroxide reduction results prove that all Ag catalysts tested are suitable for both reactions. Ag/NGO2 catalyst possesses the highest mass activity for ORR, which indicates a relationship between the Ag loading and electrocatalytic activity. The electroreduction ...
Scientific Reports, 2013
A series of edge-selectively halogenated (X 5 Cl, Br, I) graphene nanoplatelets (XGnPs 5 ClGnP, BrGnP, IGnP) were prepared simply by ball-milling graphite in the presence of Cl 2 , Br 2 and I 2 , respectively. High BET surface areas of 471, 579 and 662 m 2 /g were observed for ClGnP, BrGnP and IGnP, respectively, indicating a significant extent of delamination during the ball-milling and subsequent workup processes. The newly-developed XGnPs can be well dispersed in various solvents, and hence are solution processable. Furthermore, XGnPs showed remarkable electrocatalytic activities toward oxygen reduction reaction (ORR) with a high selectivity, good tolerance to methanol crossover/CO poisoning effects, and excellent long-term cycle stability. First-principle density-functional calculations revealed that halogenated graphene edges could provide decent adsorption sites for oxygen molecules, in a good agreement with the experimental observations. O ne of the major hurdles for commercialization of the fuel cell technology is the sluggish oxygen reduction reaction (ORR) at cathode 1-3. So far, high cost and scarce precious platinum (Pt) and its alloys have been considered to be the most reliable cathodic ORR electrocatalysts in fuel cells 4-8. In addition to the high cost, however, Pt and its alloys are also suffered from methanol crossover/carbon monoxide (CO) poisoning effects and poor operation stability. Therefore, it is essential to search for non-precious metal 9-11 or metal-free 12-17 electrocatalysts with a high catalytic activity and long-term operation stability to reduce or replace Pt-based ORR electrocatalysts in fuel cells. Although extensive efforts have been devoted to the development of non-precious metal-based electrocatalysts, their practical application is still out of sight due largely to their limited electrocatalytic activity, poor cycle stability and sometimes environmental hazard. Recently, carbon-based materials doped with heteroatoms, such as boron (B) 14,18 , halogen (Cl, Br, I) 19,20 , nitrogen (N) 12,15,21-25 , phosphorus (P) 26 , sulfur (S) 27 , and their mixtures 28-30 , have attracted tremendous attentions as metal-free ORR eletrocatalysts. The difference in electronegativity (x) between the heteroatom dopants (B 5 2.04, I 5 2.66, N 5 3.04, P 5 2.19 and S 5 2.58) and carbon atom (2.55) 31 in covalently doped graphitic carbon frameworks can polarize adjacent carbon atoms. Indeed, quantum mechanics calculations revealed that the electron accepting/donating ability of the heteroatom dopants created net positive/negative charges on adjacent carbon atoms in graphitic lattice to facilitate the oxygen reduction process 12. Thus, both the vertically-aligned nitrogen-doped carbon nanotubes (VA-NCNTs) 12 and nitrogen-doped graphene (N-graphene) 25 catalyzed an efficient four-electron ORR process with a higher electrocatalytic activity and better operation stability than the commercially available Pt/C-based electrocatalyst (Pt: 20 wt%, Vulcan XC-72R). Furthermore, the excellent stability over the methanol crossover/CO poisoning effects is additional advantage of these carbon-based metal-free catalysts. Although the basic catalytic mechanism has been established, the full potential of these
Electrochimica Acta, 2015
Here we report the oxygen reduction reaction (ORR) activity of Ag nanoparticles supported on boron doped multi-walled carbon nanotubes (Ag/B-MWCNTs) with different Ag loadings synthesized by a facile chemical method. Transmission electron microscopy (TEM) and X-ray diffraction patterns (XRD) measurements were employed to investigate the morphology and crystal structure of the as-prepared catalysts. The electrochemical results demonstrated that all the Ag/B-MWCNTs samples catalyzed the ORR in alkaline media by an efficient four-electron pathway. Furthermore, Ag/B-MWCNTs with lowest Ag loading (20%) performed the highest mass activity towards ORR mainly due to the synergistic effect of Ag nanoparticles and B-MWCNTs. This work brings insight into the role of supporting materials in reducing the loading of metal catalyst towards low-cost ORR in alkaline media.
Electrocatalysis, 2018
Silver-iron carbon nitride, which has been prepared by pyrolysis (under inert atmosphere) of silver hexacyanoferrate(II) deposited on graphene nanoplatelets, is considered here as electrocatalyst for oxygen reduction in alkaline medium (0.1 M potassium hydroxide electrolyte) in comparison to simple silver nanoparticles and iron carbon nitride (prepared separately in a similar manner on graphene nanoplatelets). The performance of catalytic materials has been examined using such electrochemical diagnostic techniques as cyclic voltammetry and rotating ring-disk electrode voltammetry. Upon application of the graphene nanoplatelet-supported mixed silver-iron carbon nitride catalyst, the reduction of oxygen proceeds at more positive potentials, as well as the amounts of hydrogen peroxide (generated during reduction of oxygen at potentials more positive than 0.3 V) are lower relative to those determined at pristine silver nanoparticles and iron carbon nitride (supported on graphene nanoplatelets), when they have been examined separately. The enhancement effect shall be attributed to high activity of silver toward the reduction/ decomposition of H 2 O 2 in basic medium. Additionally, it has been observed that the systems based on carbon nitrides show considerable stability due to strong fixation of metal complexes to CN shells.