Showing papers on "Catalyst support published in 2014"

CoSe2 Nanoparticles Grown on Carbon Fiber Paper: An Efficient and Stable Electrocatalyst for Hydrogen Evolution Reaction

Abstract: Development of a non-noble-metal hydrogen-producing catalyst is essential to the development of solar water-splitting devices. Improving both the activity and the stability of the catalyst remains a key challenge. In this Communication, we describe a two-step reaction for preparing three-dimensional electrodes composed of CoSe2 nanoparticles grown on carbon fiber paper. The electrode exhibits excellent catalytic activity for a hydrogen evolution reaction in an acidic electrolyte (100 mA/cm2 at an overpotential of ∼180 mV). Stability tests though long-term potential cycles and extended electrolysis confirm the exceptional durability of the catalyst. This development offers an attractive catalyst material for large-scale water-splitting technology.

Ultrathin Cobalt–Manganese Layered Double Hydroxide Is an Efficient Oxygen Evolution Catalyst

Abstract: Cost-effective production of solar fuels requires robust and earth-abundant oxygen evolution reaction (OER) catalysts. Herein, we report that ultrathin nanoplates of cobalt–manganese layered double hydroxide (CoMn LDH) are a highly active and stable oxygen evolution catalyst. The catalyst was fabricated by a one-pot coprecipitation method at room temperature, and its turnover frequency (TOF) is more than 20 times higher than the TOFs of Co and Mn oxides and hydroxides, and 9 times higher than the TOF of a precious IrO2 catalyst. The activity of the catalyst was promoted by anodic conditioning, which was proposed to form amorphous regions and reactive Co(IV) species on the surface. The stability of the catalyst was demonstrated by continued electrolysis.

Carbon Materials as Catalyst Supports and Catalysts in the Transformation of Biomass to Fuels and Chemicals

Abstract: Carbon plays a dual role as a catalyst or a catalyst support for chemical and enzymatic biomass transformation reactions due to its large specific surface area, high porosity, excellent electron conductivity, and relative chemical inertness. Advantageously, carbon materials can be prepared from residual biomass, an attractive property for decreasing the so-called “carbon-footprint” of a biomass transformation process. Carbon can be chemically functionalized and/or decorated with metallic nanoparticles and enzymes to impart or improve novel catalytic activity. Sulfonated porous carbon materials exhibit high reactivity in diversified catalytic reactions compared to their nonporous counterparts. However, the SO3H groups prevent the incorporation of hydrophobic molecules into the bulk, thereby causing hydrophobic acid-catalyzed reactions to proceed only on the surface. Metal and enzymatic catalysts on carbon supports have significant advantages over other oxide materials for different types of reactions. The ...

Hydrogen evolution from a copper(I) oxide photocathode coated with an amorphous molybdenum sulphide catalyst

Abstract: Photoelectrochemical water splitting may be used to produce hydrogen using abundant solar energy. Here, the authors fabricate layered films of amorphous molybdenum sulphide on copper(I) oxide and demonstrate the catalytic activity and enhanced stability of these devices made from earth-abundant materials.

A Review of Graphene‐Based Nanostructural Materials for Both Catalyst Supports and Metal‐Free Catalysts in PEM Fuel Cell Oxygen Reduction Reactions

Abstract: A comprehensive overview and description of graphene-based nanomaterials explored in recent years for catalyst supports and metal-free catalysts for polymer electrolyte membrane (PEM) fuel cell oxygen reduction reactions (ORR) is presented. The catalyst material structures/morphologies, material selection, and design for synthesis, catalytic performance, catalytic mechanisms, and theoretical approaches for catalyst down-selection and catalyzed ORR mechanisms are emphasized with respect to the performance of ORR catalysts in terms of both activity and stability. When graphene-based materials, including graphene and doped graphene, are used as the supporting materials for both Pt/Pt alloy catalysts and non-precious metal catalyst, the resulting ORR catalysts can give superior catalyst activity and stability compared to those of conventional carbon-supported catalysts; when they are used as metal-free ORR catalysts, significant catalytic activity and stability are observed. The nitrogen-doped graphene materials even show superior performance compared to supported metal catalysts. Challenges including the lack of material mass production, unoptimized catalyst structure/morphology, insufficient fundamental understanding, and testing tools/protocols for performance optimization and validation are identified, and approaches to address these challenges are suggested.

Review on latest developments in biodiesel production using carbon-based catalysts

Abstract: Catalyst plays an important role in biodiesel production. Owing to the advantages of heterogeneous catalysts in terms of separation and reusability over the traditionally used homogeneous catalyst, the research has now been focused on these heterogeneous catalysts in recent years. In order to make the process fully “green”, researchers are trying to prepare catalysts from renewable sources such as biomass. Within this concept the carbon based catalysts have been introduced. Carbon based materials are considered as ideal catalysts due to desirable features such as low material cost, high surface area and thermal stability. They are easily prepared by functionalizing carbon surface with acids or bases; in other cases carbon material was reported to be used as a support. Additionally, the carbon could be produced from most of the waste generated in different industrial processes. Therefore, its utilization as catalyst makes the biodiesel production a “greener” one. Under optimal conditions biodiesel (FAME) yields up to 90–98.3% were reported over various carbon based catalysts.

Titanium Dioxide as a Catalyst Support in Heterogeneous Catalysis

Abstract: The lack of stability is a challenge for most heterogeneous catalysts. During operations, the agglomeration of particles may block the active sites of the catalyst, which is believed to contribute to its instability. Recently, titanium oxide (TiO2) was introduced as an alternative support material for heterogeneous catalyst due to the effect of its high surface area stabilizing the catalysts in its mesoporous structure. TiO2 supported metal catalysts have attracted interest due to TiO2 nanoparticles high activity for various reduction and oxidation reactions at low pressures and temperatures. Furthermore, TiO2 was found to be a good metal oxide catalyst support due to the strong metal support interaction, chemical stability, and acid-base property. The aforementioned properties make heterogeneous TiO2 supported catalysts show a high potential in photocatalyst-related applications, electrodes for wet solar cells, synthesis of fine chemicals, and others. This review focuses on TiO2 as a support material for heterogeneous catalysts and its potential applications.

Quantification of Zinc Atoms in a Surface Alloy on Copper in an Industrial-Type Methanol Synthesis Catalyst

Abstract: Methanol has recently attracted renewed interest because of its potential importance as a solar fuel.1 Methanol is also an important bulk chemical that is most efficiently formed over the industrial Cu/ZnO/Al2O3 catalyst. The identity of the active site and, in particular, the role of ZnO as a promoter for this type of catalyst is still under intense debate.2 Structural changes that are strongly dependent on the pretreatment method have now been observed for an industrial-type methanol synthesis catalyst. A combination of chemisorption, reaction, and spectroscopic techniques provides a consistent picture of surface alloying between copper and zinc. This analysis enables a reinterpretation of the methods that have been used for the determination of the Cu surface area and provides an opportunity to independently quantify the specific Cu and Zn areas. This method may also be applied to other systems where metal–support interactions are important, and this work generally addresses the role of the carrier and the nature of the interactions between carrier and metal in heterogeneous catalysts.

Metal organic framework derived magnetic porous carbon composite supported gold and palladium nanoparticles as highly efficient and recyclable catalysts for reduction of 4-nitrophenol and hydrodechlorination of 4-chlorophenol

Abstract: The development of low cost noble metal nanocatalysts with high activity and selectivity, high catalytic performance, convenient separation, and reusability is a significant challenge. Herein, the magnetic porous carbon (MPC) composite synthesized from metal organic framework (MOF) was used as a catalyst support to fabricate gold (Au) and palladium (Pd) nanoparticle (NP) based nanocatalysts. The MPC not only provided a large surface area and mesopores on which the active centers (Au and Pd NPs) were finely dispersed, but also exhibited superparamagnetic behaviour that enabled the magnetic separation and convenient recovery of the nanocatalysts from the reaction mixture. Thus, the nanocatalysts were repeatedly used without loss of catalytic efficiency. Both the Au/MPC and Pd/MPC nanocatalysts showed excellent catalytic activity for the reduction of 4-nitrophenol. Moreover, the Pd/MPC nanocatalyst exhibited higher efficiency toward hydrodechlorination of 4-chlorophenol compared to the other reported catalysts. This study indicated that the noble metal NPs (NMNPs) supported on MOF-derived MPC materials could act as promising catalysts exhibiting potential applications in numerous NMNP based catalytic reactions.

Graphene–Co3O4 nanocomposite as an efficient bifunctional catalyst for lithium–air batteries

Abstract: A facile hydrothermal route has been developed to prepare graphene–Co3O4 nanocomposites. The graphene–Co3O4 nanocomposite catalyst demonstrates an excellent catalytic activity toward oxygen-reduction reaction including a considerably more positive half-wave potential (−0.23 V) than that of pristine graphene (−0.39 V), as well as higher cathodic currents. More importantly, this catalyst shows better long-term durability than the commercial Pt/C catalyst in an alkaline solution. The preliminary results indicate that the graphene–Co3O4 nanocomposite is an efficient and stable bifunctional catalyst for Li–air batteries and may be an alternative to the high-cost commercial Pt/C catalyst for the ORR/OER in alkaline solutions.

Surface Al leached Ti3AlC2 as a substitute for carbon for use as a catalyst support in a harsh corrosive electrochemical system

Abstract: Surface Al leached Ti3AlC2 particles (e-TAC) with high corrosion resistance and excellent electrical conductivity were developed as an advanced support material for Pt catalysts. Electrochemical measurements confirm that the supported Pt/e-TAC electrocatalyst shows much improved activity and enhanced durability toward the oxygen reduction reaction when compared with the commercial Pt/C catalyst.

Immobilized Transition Metals as Catalysts for Cross‐Couplings in Continuous Flow—A Critical Assessment of the Reaction Mechanism and Metal Leaching

Abstract: In the not too distant future many industrially important chemicals (including pharmaceuticals) will probably be manufactured using continuous flow technology. For a significant number of synthetic steps involved in these protocols transition metal (mostly palladium)-catalyzed carbon–carbon or carbon–heteroatom bond forming reactions (“cross-coupling chemistry”) will play an important role. Designing a process for continuous cross-coupling chemistry involves either the use of a homogeneous or of a heterogeneous (immobilized) catalyst/ligand system. In the latter case, the catalyst/ligand system is typically in the form of a packed-bed reactor, through which the reaction mixture is pumped, employing an appropriate temperature regime and residence time. Although this approach has been widely popular during the past 15 years, there is growing evidence that suggests that the use of immobilized transition metal catalysts for performing cross-coupling chemistry in continuous flow is, in fact, not very practical. As demonstrated in this review, significant leaching of the transition metal out of the packed-bed catalyst will almost inevitably occur, leading to decreased catalyst activity and contamination of the product with transition metal. This is a consequence of the well-known fact that the reaction mechanism for these kinds of transformations is (quasi)homogeneous and involves the transformation of a Pd0 species into a (soluble) PdII species. Using an immobilized catalyst in a batch protocol the transient leaching of palladium will not be immediately obvious, as, after completion of the catalytic cycle, Pd0 will typically redeposit onto the support. In contrast, in continuous flow mode, the palladium metal will progressively be “chromatographed” through the packed-bed catalyst until, ultimately, all palladium will be removed from the support. This effect typically will become only evident when long run experiments are performed. The preferred alternative, in particular for larger scale experiments, is to use a homogeneous (pre)catalyst in combination with an appropriate catalyst recycling technology.

Development of highly stable catalyst for methanol synthesis from carbon dioxide

Abstract: Zr-doped Cu-Zn-Zr-Al (CZZA) catalyst showed excellent performances for the methanol synthesis from carbon dioxide and hydrogen such as activity, selectivity and especially stability under mild conditions (such as 230 °C and 3.0 MPa). The catalyst showed excellent tolerance against water vapor. It was found that added alumina promoted the dispersion of Cu whereas it suppressed the reduction of copper oxide. On the other hand, added Zr promoted the catalytic activity of methanol synthesis from CO 2 and suppressed the inhibitive effect of water for the reaction as well as the catalyst deactivation. It was concluded that the methanol formation from CO 2 proceeds through two routes: one is the direct hydrogenation of CO 2 to methanol and another is the one which pass through the CO formation. The Zr-promoted catalyst gave methanol and CO at the selectivity ratio of 0.4 to 0.6, whereas the un-promoted catalyst gave only CO at the initial stage of the reaction. It was claimed that the doped Zr promote the in-situ reduction of oxidized Cu (which should be caused by the reaction with the co-product H 2 O) by H 2 to increase the content of reduced Cu (active site) and thus the catalyst activity. The promoted reductivity of the Zr-containing catalyst prevents the crystal growth of CuO x which cause the irreversible deactivation of catalyst.

The Role of Ru and RuO2 in the Catalytic Transfer Hydrogenation of 5‐Hydroxymethylfurfural for the Production of 2,5‐Dimethylfuran

Abstract: We have previously shown that 2,5-dimethylfuran (DMF) can be produced selectively from 5-hydroxymethylfurfural in up to 80 % yield via catalytic transfer hydrogenation with 2-propanol as a hydrogen donor and Ru/C as a catalyst. Herein, we investigate the active phase of the Ru/C catalyst by using extended X-ray absorption fine structure, X-ray photoelectron spectroscopy, and high-resolution TEM analyses. The results reveal that RuO2 is the dominant phase in the fresh (active) catalyst and is reduced to metallic Ru during the reaction with the hydrogen produced in situ from 2-propanol. The deactivation of the catalyst is correlated with the reduction of the surface of RuO2. Reactivity studies of individual phases (bulk RuO2 and reduced Ru/C catalysts) indicate that RuO2 mainly catalyzes the Meerwein–Ponndorf–Verley reaction of 5-hydroxymethylfurfural that produces 2,5-bis(hydroxymethyl)furan and the etherification of 2,5-bis(hydroxymethyl)furan or other intermediates with 2-propanol and that the reduced Ru/C catalyst has moderate hydrogenolysis activity for the production of DMF (30 % selectivity) and other intermediates (20 %). In contrast, a physical mixture of the two phases increases the DMF selectivity up to 70 %, which suggests that both metallic Ru and RuO2 are active phases for the selective production of DMF. The oxidation of the reduced Ru/C catalyst at different temperatures and the in situ hydrogen titration of the oxidized Ru/C catalysts were performed to quantify the bifunctional role of Ru and RuO2 phases. The mild oxidation treatment of the Ru/C catalyst at 403 K could activate the catalyst for the selective production of DMF in up to 72 % yield by generating a partially oxidized Ru catalyst.

Perovskite LaxM1−xNi0.8Fe0.2O3 catalyst for steam reforming of toluene: Crucial role of alkaline earth metal at low steam condition

Abstract: The effect of alkaline earth metal (Mg, Ca, and Sr) substitution to LaNi 0.8 Fe 0.2 O 3 perovskite catalyst was investigated for steam reforming of toluene as a model compound of tar at various steam amounts. Catalytic performance of La 0.8 Sr 0.2 Ni 0.8 Fe 0.2 O 3 (LSNFO) catalyst at high steam condition (S/C = 3.4) is higher than the activity of La 0.8 Mg 0.2 Ni 0.8 Fe 0.2 O 3 (LMNFO) and La 0.8 Ca 0.2 Ni 0.8 Fe 0.2 O 3 (LCNFO) catalysts due to higher amount of active sites and higher amount of lattice oxygen on LSNFO catalyst. However, the activity of LSNFO catalyst is still lower than the activity of LaNi 0.8 Fe 0.2 O 3 (LNFO) catalyst even though carbon deposition on spent LSNFO catalyst is the lowest among other catalysts. Interestingly, the activity of LSNFO catalyst is comparable with the activity of LNFO catalyst at S/C of 2 and outperforms LNFO catalyst at S/C of 1. Moreover, the carbon deposition on LNFO catalyst increases with increasing temperature while it decreases with increasing temperature on LSNFO catalyst due to lattice oxygen desorbed at 700–800 °C. Further characterization shows that water is adsorbed strongly on LSNFO catalyst and is only able to desorb at higher temperature near the reaction temperature. This strongly adsorbed water property of LSNFO catalyst enables this catalyst to have better catalytic performance at low steam condition.

Catalyst Enhancement and Recyclability by Immobilization of Metal Complexes onto Graphene Surface by Noncovalent Interactions

Abstract: The immobilization of a homogeneous catalyst onto a solid surface is one of the major challenges in catalysis, because it may facilitate the separation of the catalyst and the reaction products and may also give rise to the reutilization of the catalyst in multiple subsequent cycles. Noncovalent interactions between the catalyst and the support are arising as interesting alternatives to the more widely used covalent interactions, because they avoid the functionalization of both the catalyst and the surface, which may in turn lead to the modification of the inherent properties of the catalyst. However, some other problems may arise, such as leaching. In this work, we have obtained two complexes containing an N-heterocyclic carbene ligand with a pyrene tag, which we immobilized onto the surface of reduced graphene oxide (rGO), by π-stacking. The catalytic properties of the parent molecular complexes and hybrid materials have been studied in the palladium-catalyzed hydrogenation of alkenes and the ruthenium-...

Chemically Exfoliated MoS2 Nanosheets as an Efficient Catalyst for Reduction Reactions in the Aqueous Phase

Abstract: Chemically exfoliated MoS2 (ce-MoS2) nanosheets that incorporate a large fraction of metallic 1T phase have been recently shown to possess a high electrocatalytic activity in the hydrogen evolution reaction, but the potential of this two-dimensional material as a catalyst has otherwise remained mostly uncharted. Here, we demonstrate that ce-MoS2 nanosheets are efficient catalysts for a number of model reduction reactions (namely, those of 4-nitrophenol, 4-nitroaniline, methyl orange, and [Fe(CN)6]3–) carried out in aqueous medium using NaBH4 as a reductant. The performance of the nanosheets in these reactions is found to be comparable to that of many noble metal-based catalysts. The possible reaction pathways involving ce-MoS2 as a catalyst are also discussed and investigated. Overall, the present results expand the scope of this two-dimensional material as a competitive, inexpensive, and earth-abundant catalyst.

Comparative study of bimetallic Pt-Sn catalysts supported on different supports for propane dehydrogenation

Abstract: Bimetallic PtSn catalysts supported on different supports (ZSM-5, γ-Al 2 O 3 , mesoporous alumina, SBA-15) were prepared and several techniques were employed to study the influence of different supports on the catalytic structure and reaction performances. According to the results of XRD, textual properties and acid measurements for the as-prepared catalysts, the selected support is the main factor to determine the porous character and the acidic properties of the corresponding catalyst. In our experiments, when the used support is mesoporous alumina, most uniform and narrow distribution of metallic particles can be obtained. Furthermore, the presence of this support promotes the occurrence of spillover hydrogen and strengthens the interaction between Sn species and the support. As a result, the oxidative state of Sn can be stabilized and the transformation of active sites is promoted, thus improving the catalytic stability and reaction selectivity. Compared with this, the existence of the strong acid sites in ZSM-5 induces more cracking reaction and the porous character of γ-Al 2 O 3 increases the accumulation of the coke. Meanwhile, the use of SBA-15 support leads to the agglomeration of metallic particles and the easy reduction of tin species, which is disadvantageous to the reaction.

Ni/H-ZSM-5 as a promising catalyst for vapour phase hydrogenation of levulinic acid at atmospheric pressure

Abstract: Among Ni supported on H-ZSM-5 catalysts with various loadings of Ni, a catalyst with 30 weight% Ni has been identified as an effective catalyst for the hydrogenation of levulinic acid to γ-valerolactone in vapour phase at atmospheric pressure. The catalysts have been characterized by different techniques such as XRD, BET surface area, pore size distribution, TPR, AAS, pulse chemisorption, FE-SEM-EDS, TEM, XPS and pyridine-adsorbed IR. XRD patterns suggest that the structure of H-ZSM-5 is intact even after incorporation of Ni. Pyridine-adsorbed IR patterns reveal the presence of both Lewis and Bronsted acid sites, which are responsible for the dehydration and cleavage of γ-valerolactone. The superior activity exhibited by the 30 wt% Ni/H-ZSM-5 catalyst (demonstrating the highest productivity of 0.9090 kgGVL kgcatalyst−1 h−1 at 250 °C) is due to the presence of a greater number of surface Ni species. Non-noble metal Ni-based catalysts offer advantages over the present processes involving Ru-based catalysts, which have certain constraints, some of which are unavoidable such as cost ineffectiveness, the use of volatile organic solvents and high pressure operation. The 30 wt% Ni/H-ZSM-5 catalyst can be seen as an alternative and promising catalyst which could be of great importance to the chemical industry.

Highly active PdCeOx composite catalysts for low-temperature CO oxidation, prepared by plasma-arc synthesis

Abstract: The plasma-arc method was adapted for the synthesis of composite palladium–ceria catalysts, which were utilized for the low-temperature oxidation of carbon monoxide. The Pd/CeO2 catalysts were synthesized in two steps: step 1 – direct synthesis of palladium–cerium–carbon composite PdCeC in the plasma-arc chamber, and step 2 – calcination of the composite with carbon burnout in air at 600, 700, and 800 °C. Catalytic testing using temperature-programmed reaction demonstrated the high efficiency of the synthesized catalysts during the oxidation of carbon monoxide and their ability to oxidize CO at temperatures as low as room temperature. In comparison with a catalyst that had similar morphology and palladium content but was prepared by coprecipitation, the synthesized catalyst showed that the calculated TOF value for the composite catalyst was two–three times higher than that of the catalyst prepared by chemical methods. A variety of physical methods (HRTEM, XRD, XPS, Raman spectroscopy and others) were used to examine the microstructure, composition and electronic state of the composite components in detail after the high-temperature calcination stage of catalyst synthesis. It was shown that high catalytic activity was provided by the formation of a high-defect fluorite structure of PdCeOx solid solution and highly dispersed PdOx nanoparticles. The XPS data suggest that carbon nanostructures mixed with palladium and cerium in the initial PdCeC composite prevent sintering during high-temperature calcination and play a key role in the formation of a high-defect solid solution of palladium in the CeO2 structure, which has a high concentration of Ce3+ and oxygen vacancies.

Enhanced Cyclability of Li–O2 Batteries Based on TiO2 Supported Cathodes with No Carbon or Binder

Abstract: The decomposition of carbon materials and organic binders in Li–air batteries has been reported repeatedly in recent literature. The decomposition of carbon can harm the batteries’ cyclability further by catalyzing electrolyte degrading. Therefore, there is a critical need to exploit a new catalyst support substituting carbon and develop a binder free cathode preparation strategy for Li–air batteries. Herein, TiO2 nanotube arrays growing on Ti foam are used as the catalyst support to construct carbon and binder free oxygen diffusion electrodes. After being coated with Pt nanoparticles by a cool sputtering approach, the TiO2 nanotube arrays are used as cathodes of Li–O2 batteries. Benefiting from the stability of TiO2 in the discharge/charge processes, the Li–O2 batteries realize enhanced cyclability at high current densities (for instance, more than 140 cycles at 1 or 5 A g–1), within wide discharge/charge voltage windows (for instance, 1.5–4.5 V). X-ray photoelectron spectra and a scanning electron micro...

Cobalt and nitrogen co-embedded onion-like mesoporous carbon vesicles as efficient catalysts for oxygen reduction reaction

Abstract: A series of cobalt and nitrogen co-embedded onion-like mesoporous carbon vesicles (Co–NMCVs) were synthesized as non-noble metal catalysts for the first time. Physical characterization indicated that the Co–NMCVs samples all retain the lamellar porous shell structure (accompanying considerable surface areas and pore volumes), except the Co20–NMCV sample. Electrochemical measurements demonstrate that most of the Co–NMCV catalysts exhibit remarkable oxygen reduction reaction (ORR) activity in both acidic and alkaline media. Particularly, the Co10–NMCV catalyst exhibits a more positive onset voltage of −0.13 V (only 50 mV deviation from Pt/C), a higher half-wave potential of −0.18 V (only 20 mV deviation from Pt/C), and better selectivity (electron-transfer number >3.92) for the ORR in alkaline medium. Meanwhile, the Co10–NMCV catalyst also shows higher durability of the ORR catalytic activity and better methanol tolerance than the commercial Pt/C catalyst. The unprecedented performance of the Co10–NMCV catalyst in ORR is attributed to the homogeneous distribution of abundant Co–N active sites (having the dominant effect for the ORR catalytic activity) on the surface of the MCV matrix (which has the onion-like lamellar structure, high specific surface area, and large pore volume), which observably enhance the active site density of the Co10–NMCV catalyst. All experimental results demonstrate that the Co10–NMCV catalyst may be exploited as the potentially efficient and inexpensive non-noble metal ORR catalyst to replace Pt-based catalysts.

Extraordinary Hydrogen Evolution and Oxidation Reaction Activity from Carbon Nanotubes and Graphitic Carbons

Abstract: The hydrogen evolution reaction, 2H(+) + 2e(–) → H2, and its converse, the hydrogen oxidation reaction, H2 → 2H(+) + 2e(–), are central to any realization of a hydrogen economy. Various forms of carbon have been used for decades as the precious metal catalyst support in these reactions. Here we report the unexpected result that single-wall carbon nanotubes and some graphitic carbons, activated by brief exposure to electrochemical potentials that induce hydrogen evolution in intercalating acids combined with extended soak times in such acids, acquire an activity for these reactions that exceeds that of known nonprecious metal catalysts.