High Area Carbon Research Articles

High performance bagasse based iron–nitrogen-carbon catalyst for oxygen reduction reaction

The design and synthesis of highly stable and low-cost for the oxygen reduction reactions (ORR) catalysts to replace non-noble metal catalysts is crucial for their applications in fuel cells. In this work, bagasse activated carbon (BAC) was used as the carbon source to prepare the high specific area and multi-porous carbon. The BAC@FeN catalysts derived from BAC, FeCl2 and melamine were prepared by pre-activation treatment and high-temperature pyrolysis. The BAC@FeN-900–30 catalyst encapsulated with Fe3C and Fe3O4 exhibited an outstanding catalytic activity (Eonset = 1.01 V and E1/2 = 0.87 V) and superior operational stability of 90.50 % compared to Pt/C (20 wt%) catalyst. The results demonstrated that iron, carbon and nitrogen piggybacked BAC could generate abundant Fe-Nx active sites, which greatly improved the catalytic activity of ORR and had a broad application prospect in energy conversion.

Palladium-copper bimetallic surfaces as electrocatalysts for the ethanol oxidation in an alkaline medium

Two types of Cu-modified Pd catalysts supported on high area carbon were prepared: Pd nanoparticles modified with a sub-monolayer of underpotentially deposited Cu (Cu@Pd/C) and Pd-Cu alloy nanoparticles (Pd-Cu/C), and examined for the ethanol oxidation reaction (EOR) in alkaline solution. The catalysts were characterized by energy-dispersive X-ray spectroscopy, X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy, as well as cyclic voltammetry. As reference catalysts, Pd/C and Pt/C were used. The electrochemically active surface area of all samples was determined from COads and Cuupd desorption and Pd oxide reduction, and used to assess their intrinsic activity for EOR. Intimate contact of Pd with Cu atoms enhanced its activity, regardless of the type of bimetal catalyst. The atomic Pd:Cu ratio between 2:1 and 4:1 appears to be optimal for high activity. The most active catalyst under the potentiodynamic conditions was Cu@Pd/C with θ(Cu) = 0.21,although Pd-Cu/C was superior during the potentiostatic test. All bimetallic catalysts surpassed Pd/C in mass activity. The EOR activity of Pt/C was higher compared to Pd-based catalysts at low potentials, both in terms of specific and mass activity, but with a significant decline over a 30-min potentiostatic stability test.

Porous V2O3/C composite electrodes derived from V-MOF with advanced performance for Zn-ion battery

Vanadium oxides are promising cathode materials for Zn-ion batteries. However, they are always suffered from inferior performance because of intrinsic sluggish kinetics, poor conductivity and surface elements dissolution. In this work, porous composite of V2O3 nanoparticles embedded in carbon framework is fabricated by pyrolysis of a Vanadium-base MOF. Attributing to the abundant pores, high specific area and conductive carbon framework, the obtained hierarchical composite delivers a high specific capacity of 240 mAh g−1 at 0.5 A g−1 although the content of carbon is up to 50%, and exhibits a good rate performance with 86.6% retention when the current densities increased from 0.5 to 4 A g−1. Moreover, the cycling performance of the composite is much better than that of commercial V2O3.

Fe- and Co-Containing Nitrogen-Doped Nanocarbon Catalysts from 5-Methylresorcinol for Anion Exchange Membrane Fuel Cells

Replacing fossil fuels with alternative energy sources has a growing scientific and societal interest because of the the environmental concerns related with their utilization. Low-temperature polymer electrolyte fuel cells have become a subject of intense research as the future cornerstone of renewable energy-based economy.Platinum nanoparticles supported on high-area carbon materials (Pt/C) are commonly used as the cathode catalyst in low-temperature fuel cells. However, the high cost of precious metal-based catalysts limits the commercial viability of such fuel cells. Considerable effort has been directed to design efficient and cheap electrocatalysts through the last decades and transition metal-containing nitrogen-doped carbon nanomaterials have shown the most promising results. A simple strategy to prepare these catalyst materials is high-temperature pyrolysis of organic carbon precursors in the presence of nitrogen and metal sources, where carbonization and N-doping occur simultaneously.1 In this work, highly active oxygen reduction reaction (ORR) electrocatalysts from 5-methylresorcinol, dicyandiamide (DCDA) and Fe and/or Co salts were prepared by a simple one-pot synthesis procedure.2 It has been proposed that DCDA polymerizes into graphitic carbon nitride at around 550 °C, which acts as a reactive template during carbonization of organic precursors, decomposing above 750 °C to produce the micro- and macropores necessary for efficient mass transfer and yielding N-doped graphene-like carbon structures.3 The SEM and TEM analysis revealed that the materials are composed of wrinkled carbon structures doped with nitrogen and metals, and also contain metal nanoparticles encapsulated in N-doped carbon layers. According to the XRD analysis, these nanoparticles are mainly composed of Co, Fe/Fe3O4 and FeCo alloy for the CoNC, FeNC and FeCoNC catalysts, respectively. The specific surface area of the materials was between 290 and 410 m2 g−1. The XPS analysis revealed that the catalysts contain metal-coordinated N centers, while pyridinic nitrogen is the most abundant N species in all materials. Electrocatalytic activity for ORR in alkaline media was evaluated via the rotating disk electrode (RDE) method. The ratio of the precursors was optimized and bimetallic catalysts were found to be more active toward ORR than their monometallic counterparts. Acid treatment slightly increased the catalysts’ ORR activity. The acid-treated bimetallic catalyst (FeCoNC-at) showed exceptional ORR performance, comparable to that of commercial Pt/C (20 wt%) (Figure 1a). This can be attributed to the high surface metal and nitrogen contents, which at least partly are present as nitrogen-coordinated metal (M-Nx) centers, as confirmed by inhibition of ORR in the presence of cyanide ions. The catalyst also demonstrated a rather high stability in short-time tests (15000 potential cycles) and good tolerance to methanol. The FeCoNC-at catalyst was further tested in an anion exchange membrane fuel cell (AEMFC) with hexamethyl-p-terphenyl poly(benzimidazolium) (HMP-PMBI) membrane,4 where a high value of peak power density (P max= 415 mW cm–2) was achieved (Figure 1b).2 References Sarapuu, E. Kibena-Põldsepp, M. Borghei, K. Tammeveski, Electrocatalysis of oxygen reduction on heteroatom-doped nanocarbons and transition metal–nitrogen–carbon catalysts for alkaline membrane fuel cells, J. Mater. Chem. A 6, 776–804 (2018).Kisand, A. Sarapuu, D. Danilian, A. Kikas, V. Kisand, M. Rähn, A. Treshchalov, M. Käärik, M. Merisalu, P. Paiste, J. Aruväli, J. Leis, V. Sammelselg, S. Holdcroft, K. Tammeveski, Transition metal-containing nitrogen-doped nanocarbon catalysts derived from 5-methylresorcinol for anion exchange membrane fuel cell application, J. Colloid Interface Sci. 584, 263–274 (2021).-T. Ren, Z.-Y. Yuan, A universal route to N-coordinated metals anchored on porous carbon nanosheets for highly efficient oxygen electrochemistry, J. Mater. Chem. A 7, 13591–13601 (2019).G. Wright, J. Fan, B. Britton, T. Weissbach, H.-F. Lee, E. A. Kitching, T. J. Peckham, S. Holdcroft, Hexamethyl-p-terphenyl poly(benzimidazolium): a universal hydroxide-conducting polymer for energy conversion devices, Energy Environ. Sci. 9, 2130–2142 (2016). Figure 1

ZTIFs derived nitrogen-introduced high specific area and hierarchical porous carbon for oxygen reduction reaction

ZTIFs derived nitrogen-introduced high specific area and hierarchical porous carbon for oxygen reduction reaction

Dispersion effect in formic acid oxidation on PtAu/C nanocatalyst prepared by water-in-oil microemulsion method

Low loading PtAu nanoparticles supported on high area carbon were synthesized by water-in-oil microemulsion method and examined for formic acid and methanol oxidation. Prepared catalyst powder was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). These techniques revealed that the catalyst contains rather agglomerated quasi-spherical particles, ∼4 nm diameter, composed of a solid solution of Pt and Au with only ∼4 at% of Au. In spite of such low Au content, both onset and peak potentials for CO oxidation are shifted some 150 mV to more positive values in comparison to Pt synthesized in the same manner due to stronger binding of CO as a result of notable electronic effect. It is important that this small quantity of Au also significantly influences oxidation of formic acid promoting direct path and suppressing indirect path in formic acid oxidation in a degree as expected by a much larger quantity of Au. Such improvement could be due exclusively by ensemble effect of high number of small Pt domains which formation could be possible only by very fine dispersion of such low Au quantity. High number of small Pt domains is corroborated by lower activity for methanol oxidation in comparison to Pt catalyst synthesized by the same procedure. These results emphasize the importance of the Au dispersion on the surface of Pt over its quantity in PtAu catalyst with regards to both, the ensemble and the electronic effects.

First vs. second rotation of a poplar short rotation coppice: leaf area development, light interception and radiation use efficiency

Given the high expectations for lignocellulosic biomass as one of the potential solutions for energy security and climate change mitigation, commercial scale studies over several rotations are crucial to assess the potential and the sustainability of short rotation coppice (SRC) cultures for bioenergy. The first and the second rotation of the SRC poplar (Populus) plantation of the present study differed significantly in biomass yield and in productivity determinants and their relationships. Coppicing enhanced leaf area development, radiation interception and woody biomass productivity. High total leaf area and radiation use efficiency (RUE) equally contributed to the high biomass yield during the establishment rotation, while RUE became the most important determinant of biomass yield after coppice. The study confirmed the significant genotypic variation in biomass productivity and its underlying determinants, also among more recently selected poplar genotypes. The absence of a correlation between intercepted radiation and RUE suggests the potential of selecting for genotypes combining high total leaf area and photosynthetic carbon uptake in future breeding programs for yield maximization towards sustainable bioenergy cultivation.

The Platinum∕Titanium-Nitride Interface: X-Ray Photoelectron Spectroscopy Studies

Recently published reports suggest that TiN may be a suitable support for Pt and Pt-based electrocatalysts in proton exchange membrane (PEM) fuel cells.[1] In particular, TiN is believed to exhibit higher corrosion resistance compared to high area carbons (HAC). This contribution seeks to gain insight into the nature of the interactions of metallic Pt and TiN using X-ray photoelectron spectroscopy (XPS) to probe the chemical state of the elements involved as the interface is formed.

超高比表面积碳气凝胶常压干燥制备与结构分析

超高比表面积碳气凝胶常压干燥制备与结构分析

Electrochemical instability of Pt nanoparticles probed by formic acid oxidation

A detrimental effect of CO on the stability of Pt nanoparticles, which is important for fuel cells technology, is demonstrated by the change in HCOOH kinetics on Pt nanoparticles caused by the presence of CO in the electrolyte. Pt nanoparticles supported on high area carbon (Pt/C) were applied on gold and glassy carbon substrates (Pt/C@Au and Pt/C@GC) and three different kinds of Pt surface were prepared by potential cycling in the various potential limits in N 2 and CO saturated electrolyte: untreated, OH-annealed and CO-annealed. On untreated Pt/C@Au catalyst HCOOH is oxidized predominantly through indirect mechanism, after OH-annealing direct path is slightly accelerated, but on CO-annealed catalyst the direct path in HCOOH oxidation is predominant. Based on the fact that more contiguous Pt sites are necessary for indirect than for direct path, it was concluded that OH- and especially CO-annealing of Pt/C produces small Pt domains. Since the same pretreatment did not show any effect on HCOOH oxidation on Pt/C@GC electrode, it was postulated that Pt nanoparticles dissolve in the presence of CO on the surface and in the electrolyte, and successively deposit on Au substrate. The results points out pronounced instability of Pt nanoparticles in the presence of CO.

Formic acid oxidation on Pt–Au nanoparticles: Relation between the catalyst activity and the poisoning rate

Pt–Au nanoparticles supported on high area carbon were prepared by simultaneous reduction of Au and Pt precursors and by reduction of Pt precursor on already prepared Au nanoparticles. The first method produced a solid solution of Pt in Au containing ∼5% Pt with the remaining Pt on the nanoparticles’ surface. For the Pt:Au precursor ratio of 1:4 and 1:9, the surface ratio was found to be 0.70:0.30 and 0.55:0.45, respectively. By the second method with the Pt:Au precursors ratio of 1:12, the surface ratio was 0.30:0.70. The voltammetric peaks of Pt–oxide reduction and COads oxidation demonstrated electronic modification of Pt by Au in all catalysts. With decreasing Pt:Au surface ratio the activity for HCOOH oxidation increases and surface coverage by COads decreases. The highest activity under potentiodynamic and quasi steady-state conditions without poisoning by COads was observed for the catalyst with the lowest Pt:Au surface ratio. Chronoamperometic test showed that its high catalytic activity is associated with a high deactivation rate. It was postulated that too strong adsorption of a reactive or non-reactive intermediate caused by electron modification of Pt by underlying Au, is responsible for the deactivation. This result stresses that high Pt dispersion, necessary for promotion of the dehydrogenation path in HCOOH oxidation, can produce too strong adsorption of intermediates causing deactivation of the catalyst.

Oxidation of carbon monoxide and formic acid on bulk and nanosized Pt–Co alloys

Bulk Pt3Co and nanosized Pt3Co and PtCo alloys supported on high area carbon were investigated as the electrocatalysts for the COads and HCOOH oxidation. Pt3Co alloy with Co electrochemically leached from the surface (Pt skeleton) was employed to separate electronic from ensemble and bifunctional effects of Co. Cyclic voltammetry in 0.1 M HClO4 showed reduced amount of adsorbed hydrogen on Pt sites on Pt3Co alloy compared to pure Pt. However, no significant difference in hydrogen adsorption/desorption and Pt-oxide reduction features between Pt3Co with Pt skeleton structure and bulk Pt was observed. The oxidation of COads on Pt3Co alloy commenced earlier than on Pt, but this effect on Pt3Co with Pt skeleton structure was minor indicating that bifunctional mechanism is stronger than the electronic modification of Pt by Co. The HCOOH oxidation rate on Pt3Co alloy was about seven times higher than on bulk Pt when the reaction rates were compared at 0.4 V, i.e., in the middle of the potential range for the HCOOH oxidation. Like in the case of COads oxidation, Pt skeleton showed similar activity as bulk Pt indicating that the ensemble effect is responsible for the enhanced activity of Pt3Co alloy toward HCOOH oxidation. The comparison of COads and HCOOH oxidation on Pt3Co/C and PtCo/C with the same reaction on Pt/C were qualitatively the same as on bulk materials.

Nb-doped TiO2 as a support of Pt and Pt–Ru anode catalyst for PEMFCs

Abstract TiO2 doped by 0.5% Nb was synthesized by the acid-catalyzed sol–gel method. BET surface area was determined to be 72 m2 g−1. XRD measurements showed that TiO2 has structure of anatase with ∼13 nm average crystallite size. Using Nb–TiO2 as a support, Pt/Nb–TiO2 and Pt–Ru/Nb–TiO2 were prepared by borohydride reduction method. TEM imaging of Pt–Ru/Nb–TiO2 revealed rather uniform distribution of the metallic particles on the support with a mean diameter of 3.8 nm. According to XRD analysis, Pt–Ru particles consist of the solid solution of Ru in Pt (40 at.% Ru) and a small amount of RuO2. Cyclic voltammetry of Pt/Nb–TiO2 and Pt–Ru/Nb–TiO2 indicated good conductivity of the supporting material. Oxidation of pre-adsorbed CO and methanol on Pt–Ru/Nb–TiO2 was faster than on Pt/Nb–TiO2. However, when the activities of Pt/Nb–TiO2 and Pt–Ru/Nb–TiO2 for methanol oxidation were compared to those of Pt/XC-72 and Pt–Ru/XC-72, no significant difference was observed. This means that Nb–TiO2 is a promising replacement for high area carbon supports in PEMFC anodes, but without the influence on the reaction kinetics.

Effect of pH and temperature on carbon-supported manganese oxide oxygen reduction electrocatalysts

Abstract Manganese oxides nanoparticles were chemically deposited on a high area (ca. 300 m2 g−1) carbon black substrate to act as electrocatalysts for oxygen reduction. The morphology and chemistry of the carbon-supported MnOx nanoparticles was characterised by Transmission Electron Microscopy), X-ray Diffraction, and chemical analysis. The oxygen reduction reaction (ORR) catalytic activity was studied in the 7–10 pH range using a rotating disk electrode (RDE). High activity towards oxygen reduction and very good stability in neutral and slightly basic solution were obtained. At low current densities, at 25 °C, MnOx/C displayed a reaction order with respect to OH− ions of −0.5 and Tafel slopes of −0.153 and −0.167 V dec−1 at pH 7 and 10 respectively; showing that the ORR mechanism on MnOx/C is unchanged in the 7–10 pH range. From the data, we propose that the first electrochemical step of the 4-electron ORR mechanism, in the 7–10 pH range, is the quasi equilibrium proton insertion process in MnO2 yielding MnOOH (insoluble in neutral or slightly basic solution). The ORR activity of the MnOx/C materials increased with increasing temperatures from 5 to 40 °C. The 2-electron pathway of oxygen reduction, yielding hydrogen peroxides as intermediates, may however be favoured over the 4-electron O2 reduction at higher temperatures.

Mo(VI) and W(VI) removal from water samples by acid-treated high area carbon cloth

Adsorption behavior of molybdate and tungstate from water by acid-treated carbon cloth was investigated. The carbon cloth was treated with sulfuric acid and used for the adsorption of molybdate and tungstate from water samples at nearly neutral solutions. The concentration of ions in the solution was monitored using in situ UV spectroscopy. Acid treatment caused a significant increase in the adsorption rate of ions and the adsorption capacity of the adsorbents. The adsorption isotherm data for the anions were derived at 25 °C and treated according to Langmuir and Freundlich models and was found that both models were almost equally successful. Adsorption capacities determined from Langmuir isotherms of anions showed that molybdate has greater adsorption capacity than tungstate.

Synthesis, characterization and electrocatalytic activity for ethanol oxidation of carbon supported Pt, Pt–Rh, Pt–SnO 2 and Pt–Rh–SnO 2 nanoclusters

Nanoclusters of Pt, Pt–Rh, Pt–SnO 2 and Pt–Rh–SnO 2 were successfully synthesized by polyol method and deposited on high-area carbon. HRTEM and XRD analysis revealed two phases in the ternary Pt–Rh–SnO 2/C catalyst: solid solution of Rh in Pt and SnO 2. The activity of Pt–Rh–SnO 2/C for ethanol oxidation was found to be much higher than Pt/C and Pt–Rh/C and also superior to Pt–SnO 2/C. Quasi steady-state measurements at various temperatures (30–60 °C), ethanol concentrations (0.01–1 M) and H 2SO 4 concentrations (0.02–0.5 M) showed that Pt–Rh–SnO 2/C is about 20 times more active than Pt/C in the potential range of interest for the fuel cell application.

Carbon supported electrocatalysts prepared by the sol–gel method and their utilization for the oxidation of methanol in acid media

One of the key objectives in fuel-cell technology is to improve the performance of the anode catalyst for the alcohol oxidation and reduce Pt loading. Here, we show the use of six different electrocatalysts synthesized by the sol–gel method on carbon powder to promote the oxidation of methanol in acid media. The catalysts Pt–PbOx and Pt–(RuO2–PbOx) with 10% of catalyst load exhibited significantly enhanced catalytic activity toward the methanol oxidation reaction as compared to Pt–(RuO2)/C and Pt/C electrodes. Cyclic voltammetry studies showed that the electrocatalysts Pt–PbOx/C and Pt–(RuO2–PbOx)/C started the oxidation process at extremely low potentials and that they represent a good novelty to oxidize methanol. Furthermore, quasi-stationary polarization experiments and cronoamperometry studies showed the good performance of the Pt–PbOx, Pt–(RuO2–PbOx)/C and Pt–(RuO2–IrO2)/C catalysts during the oxidation process. Thus, the addition of metallic Pt and PbOx onto high-area carbon powder, by the sol–gel route, constitutes an interesting way to prepare anodes with high catalytic activity for further applications in direct methanol fuel cell systems.

Oxygen reduction on high-area carbon cloth-supported oxide nanoparticles/polypyrrole composite electrodes

Composite electrodes on glassy carbon (GC) having the structure GC/CC(Ox)/PPy, with CC representing carbon cloth, PPy polypyrrole and Ox mixed valence spinel oxide nanoparticles of transition metals Cu 1.4Mn 1.6O 4, exhibit high reactivity and stability towards the oxygen reduction reaction (ORR), when the ORR proceeds electrocatalytically on the oxide particles dispersed throughout the carbon cloth. PPy here is electrochemically polymerized and serves as a protective layer to make the oxide sandwiched between PPy and CC fiber backbone. In oxygen saturated 0.15 M KCl solution, the composite electrodes show a good performance with current density up to 10 mA cm − 2 under gentle stirring. The enhancements of the composite electrodes for ORR result from the oxide nanoparticles dispersed on high-area CC. Optimal oxide loadings were encountered at 3.5 mg cm − 2 .

Electrochemical synthesis of hydrogen peroxide: Rotating disk electrode and fuel cell studies

The electrochemical reduction of oxygen on various catalysts was studied using the thin-layer rotating disk electrode (RDE) method. High-surface-area carbon was modified with an anthraquinone derivative and gold nanoparticles. Polytetrafluoroethylene (PTFE) and cationic polyelectrolyte (FAA) were used as binders in the preparation of thin-film electrodes. Our primary goal was to find a good electrocatalyst for the two-electron reduction of oxygen to hydrogen peroxide. All electrochemical measurements were carried out in 0.1 M KOH. Cyclic voltammetry was used in order to characterise the surface processes of the modified electrodes in O2-free electrolyte. The RDE results revealed that the carbon-supported gold nanoparticles are active catalysts for the four-electron reduction of oxygen in alkaline solution. Anthraquinone-modified high-area carbon catalyses the two-electron reduction at low overpotentials, which is advantageous for hydrogen peroxide production.

The Effect of Dynamic and Steady State Voltage Excursions on the Stability of Carbon Supported Pt and PtCo Catalysts

To improve the stability of Pt-based catalysts to meet the targets set for automotive fuel cell operation, a detailed understanding of the mechanisms of corrosion and Pt particle stability is required. The stability of Pt and PtCo on both high-area and low-area carbon supports has been studied using both dynamic and steady state voltage excursion measurements. At 1.2V steady state, the catalysation of carbon did not significantly increase the rate of carbon corrosion. However, corrosion rates of the low area carbon was 1/20th that of the high-area carbon. Under dynamic cycling, the stability of small Pt particles was found to be poor due to dissolution/sintering on the high-area carbon, however the PtCo alloy particles were found to be very stable on both the high-area and low-area carbons. In addition, it has been found that Pt oxide/reduction can catalyse carbon corrosion with both high and low-area carbons.