Defective Nitrogen-Doped Graphene Foam: A Metal-Free, Non-Precious Electrocatalyst for the Oxygen Reduction Reaction in Acid

Liu, Jianfeng; Daio, Takeshi; Orejon, Daniel; Sasaki, Kazunari; Lyth, Stephen Matthew

doi:10.1149/2.095404jes

Cited by 44 publications

(38 citation statements)

References 42 publications

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“…This model catalyst study can be extended for uniform FeO layer deposition over porous substrate surfaces, [63][64][65][66] which are technologically desirable for achieving high specific surface areas of reaction in different applications including the water gas shift reaction, H 2 O splitting, and the oxidation of CO. Table S1: The values used for the EAL calculations in NIST SRD-82. 47 Table S2-S4: Comparison of the height of different features.…”

Section: Discussionmentioning

confidence: 99%

Atomic Layer Deposition of FeO on Pt(111) by Ferrocene Adsorption and Oxidation

et al. 2015

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We report the synthesis of a sub-monolayer thick film of FeO(111) on the Pt(111) surface using atomic layer deposition (ALD) under well-defined ultra high vacuum (UHV) conditions. FeO islands were characterized by scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS) and high-resolution electron energy loss spectroscopy (HREELS). FeO(111) on Pt(111) was prepared through adsorption and oxidation of ferrocene. Because ferrocene adsorption is crucial to the overall process, it was studied in detail at different exposures and temperatures. At low exposures and at 300 K, ferrocene was found to adsorb dissociatively mainly as Cp (cyclopentadienyl ring). At high exposures, molecular adsorption dominated, and the dissociation fragments were replaced with ferrocene molecules. The adsorbed ferrocene desorbed from the Pt(111) surface at a temperature between 473 and 573 K. FeO(111) islands were grown by exposing the ferrocene adlayer to 1×10 -6 mbar O 2 at 623 K resulted in islands with the shape of truncated triangles and hexagons. The resulting surface was free of carbon, which presumably oxidized and desorbed as CO 2 . The FeO islands had a uniform height of 0.15 nm as measured by STM, and the FeO coverage could be controlled by the number of ferrocene adsorption/oxidation cycles. Due to rotational and lattice mismatches between FeO(111) and Pt (111), a pattern with approximately 2 nm periodicity was observed. In UHV, FeO began to decompose at a temperature between 673 and 873 K. Annealing in O 2 at 873 K also resulted in a net decrease of FeO amount through iron dissolution in the platinum bulk.

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Section: Discussionmentioning

confidence: 99%

Atomic Layer Deposition of FeO on Pt(111) by Ferrocene Adsorption and Oxidation

et al. 2015

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“…Crystalline materials generally have welldefined XRD peaks, while amorphous materials result in a broad body ground with shallow peaks. The GO has a strong (001) peak at 2h ¼ 9:71 and d-spacing is 0.91 nm, which is the preferred orientation of GO basal planes parallel to the sample plane (Blanton and Majumdar 2012;Liu et al 2014). …”

Section: Characterization Of Nitrogen-doped Graphenementioning

confidence: 99%

“…The NDG peaks are fairly small and broad, reflecting the defective nature of NDG, as well as the highly porous nature. It shows that only a few layers are stacked together, which result in a very low inter-layer spacing signal (Blanton and Majumdar 2012;Liu et al 2014).…”

Section: Characterization Of Nitrogen-doped Graphenementioning

confidence: 99%

Experimental and numerical investigation of the effective electrical conductivity of nitrogen-doped graphene nanofluids

et al. 2015

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Electrical conductivity is an important property for technological applications of nanofluids that have not been widely investigated, and few studies have been concerned about the electrical conductivity. In this study, nitrogen-doped graphene (NDG) nanofluids were prepared using the two-step method in an aqueous solution of 0.025 wt% Triton X-100 as a surfactant at several concentrations (0.01, 0.02, 0.04, 0.06 wt%). The electrical conductivity of the aqueous NDG nanofluids showed a linear dependence on the concentration and increased up to 1814.96 % for a loading of 0.06 wt% NDG nanosheet. From the experimental data, empirical models were developed to express the electrical conductivity as functions of temperature and concentration. It was observed that increasing the temperature has much greater effect on electrical conductivity enhancement than increasing the NDG nanosheet loading. Additionally, by considering the electrophoresis of the NDG nanosheets, a straightforward electrical conductivity model is established to modulate and understand the experimental results.

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“…To avoid the presence of transition metals, our group began synthesis of nitrogen-doped graphene foam via thermal decomposition of sodium alkoxides and subsequent heat-treatment. 30,31 Due to the high surface area and unique structure of these electrocatalysts, the ORR currents achieved were much higher than those previously obtained. Due to the purity of the precursors, and the synthesis in Teflon vessels, such samples are proven to be free of metal contamination.…”

mentioning

confidence: 83%

“…This sample is herein referred to as CN x -1000. 31 The second sample was subjected to the same process, and then graphitized at 1400…”

Section: Methodsmentioning

confidence: 99%

Metal-Free Nitrogen-Doped Carbon Foam Electrocatalysts for the Oxygen Reduction Reaction in Acid Solution

Liu

Yu²,

Daio

et al. 2016

J. Electrochem. Soc.

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Metal-free, nitrogen-doped carbon foam is utilized as a model non-precious electrocatalyst system to investigate the role of nitrogen in the oxygen reduction reaction (ORR) in the absence of iron contamination. This graphene-like foam displays relatively high activity for the ORR in acid, despite being proven free from transition-metal impurities. The onset potential is 0.85 V RHE , the mass activity is 2.8 A/g at 0.6 V RHE , and the current density is −4.0 mA/cm 2 . The maximum electron transfer number is calculated to be 3.6, revealing that a 4-electron pathway is possible in nitrogen-doped carbon, even in the absence of transition-metal coordination sites. The excellent electrochemical activity is attributed to the large surface area (700 m 2 /g), improved conductivity after graphitization, and the relatively high proportion of tertiary (graphite-like) nitrogen. Non-platinum group metal (non-PGM) electrocatalysts for the oxygen reduction reaction (ORR) are desired in order to reduce the cost and improve the durability of proton exchange membrane fuel cells (PEMFCs). Transition metal-based electrocatalysts have long been suggested as alternative electrocatalysts. Starting in the 1970's, early attempts were made to utilize transition metal-containing macrocyclic complexes as biomimetric ORR electrocatalysts, taking inspiration from their usefulness in nature.1 However, soon it was discovered that heat-treatment of these macrocycles resulted in better activity and durability, 2 leading to debate over the precise chemical composition of the active site. Later still, it was realized that the macrocyclic complex was not necessary at all, but that seemingly arbitrary mixtures of Fe (or Co), nitrogen and carbon could lead to very active electrocatalysts. 3Since then, a vast amount of research output has been produced from a number of groups across the world. [4][5][6][7][8] In recent years, such electrocatalysts have become a mainstream research topic, with the DOE setting specific targets for a non-PGM cathode in a H 2 /air PEMFC; namely a volumetric activity of 300 A/cm 3 measured at 800 mV iR-free by 2017. 9 These targets have been all but met, 10 and non-PGM electrocatalysts are now commercially available.The issue of the nature of the active site has never gone away, and is still frequently debated.11 Complicating the issue is the fact that the ORR can proceed via either a 4-or 2-electron pathway to produce water or hydrogen peroxide (which can then further decompose to water), respectively. The 4-electron pathway is most desired in fuel cells, but the 2-electron pathway is significantly present in most non-precious electrocatalysts. The consensus in recent years has drifted toward the active site being comprised of pyridinic nitrogen atoms near a defect or edge, coordinated with a transition metal atom, with strong evidence of this provided by Mossbauer spectroscopy. 12 The clustering of nitrogen atoms in this manner has been observed in graphene in high resolution scanning tunneling microscopy (STM) measuremen...

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Defective Nitrogen-Doped Graphene Foam: A Metal-Free, Non-Precious Electrocatalyst for the Oxygen Reduction Reaction in Acid

Cited by 44 publications

References 42 publications

Atomic Layer Deposition of FeO on Pt(111) by Ferrocene Adsorption and Oxidation

Atomic Layer Deposition of FeO on Pt(111) by Ferrocene Adsorption and Oxidation

Experimental and numerical investigation of the effective electrical conductivity of nitrogen-doped graphene nanofluids

Metal-Free Nitrogen-Doped Carbon Foam Electrocatalysts for the Oxygen Reduction Reaction in Acid Solution

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