Noble metal

About: Noble metal is a research topic. Over the lifetime, 15113 publications have been published within this topic receiving 337947 citations.

Molybdenum-Carbide-Modified Nitrogen-Doped Carbon Vesicle Encapsulating Nickel Nanoparticles: A Highly Efficient, Low-Cost Catalyst for Hydrogen Evolution Reaction

Abstract: Despite being promising substitutes for noble metal catalysts used in hydrogen evolution reaction (HER), the nonprecious metal catalysts (NPMCs) based on inexpensive and earth-abundant 3d transition metals (TMs) are still practically unfeasible due mainly to unsatisfactory activity and durability. Herein, a highly active and stable catalyst for HER has been developed on the basis of molybdenum-carbide-modified N-doped carbon vesicle encapsulating Ni nanoparticles (MoxC-Ni@NCV). This MoxC-Ni@NCV material was synthesized simply by the solid-state thermolysis of melamine-related composites of oxalate and molybdate with uniform Ni ions doping (Ni@MOM-com). Notably, the prepared MoxC-Ni@NCV was almost the most efficient NPMCs for HER in acidic electrolyte to date. Besides good long-term stability, MoxC-Ni@NCV exhibited a quiet low overpotential that was comparable to Pt/C. Thus, this work opens a new avenue toward the development of highly efficient, inexpensive HER catalysts.

Efficient noble metal-free (electro)catalysis of water and alcohol oxidations by zinc-cobalt layered double hydroxide.

Abstract: Replacing rare and expensive noble metal catalysts with inexpensive and earth-abundant ones for various renewable energy-related chemical processes as well as for production of high value chemicals is one of the major goals of sustainable chemistry Herein we show that a bimetallic Zn–Co layered double hydroxide (Zn–Co–LDH) can serve as an efficient electrocatalyst and catalyst for water and alcohol oxidation, respectively In the electrochemical water oxidation, the material exhibits a lower overpotential, by ∼100 mV, than monometallic Co-based solid-state materials (eg, Co(OH)2 and Co3O4)-catalytic systems that were recently reported to be effective for this reaction Moreover, the material’s turnover frequency (TOF) per Co atoms is >10 times as high as those of the latter at the same applied potentials The Zn–Co–LDH also catalyzes oxidation of alcohols to the corresponding aldehydes or ketones at relatively low temperature, with moderate to high conversion and excellent selectivity

Single-atom catalysts for CO2 electroreduction with significant activity and selectivity improvements

Abstract: A single-atom catalyst (SAC) has an electronic structure that is very different from its bulk counterparts, and has shown an unexpectedly high specific activity with a significant reduction in noble metal usage for CO oxidation, fuel cell and hydrogen evolution applications, although physical origins of such performance enhancements are still poorly understood. Herein, by means of density functional theory (DFT) calculations, we for the first time investigate the great potential of single atom catalysts for CO2 electroreduction applications. In particular, we study a single transition metal atom anchored on defective graphene with single or double vacancies, denoted M@sv-Gr or M@dv-Gr, where M = Ag, Au, Co, Cu, Fe, Ir, Ni, Os, Pd, Pt, Rh or Ru, as a CO2 reduction catalyst. Many SACs are indeed shown to be highly selective for the CO2 reduction reaction over a competitive H2 evolution reaction due to favorable adsorption of carboxyl (*COOH) or formate (*OCHO) over hydrogen (*H) on the catalysts. On the basis of free energy profiles, we identified several promising candidate materials for different products; Ni@dv-Gr (limiting potential UL = −0.41 V) and Pt@dv-Gr (−0.27 V) for CH3OH production, and Os@dv-Gr (−0.52 V) and Ru@dv-Gr (−0.52 V) for CH4 production. In particular, the Pt@dv-Gr catalyst shows remarkable reduction in the limiting potential for CH3OH production compared to any existing catalysts, synthesized or predicted. To understand the origin of the activity enhancement of SACs, we find that the lack of an atomic ensemble for adsorbate binding and the unique electronic structure of the single atom catalysts as well as orbital interaction play an important role, contributing to binding energies of SACs that deviate considerably from the conventional scaling relation of bulk transition metals.

Influence of particle agglomeration on the catalytic activity of carbon-supported Pt nanoparticles in CO monolayer oxidation

Abstract: Fuel cell electrocatalysts usually feature high noble metal contents, and these favour particle agglomeration. In this paper a variety of synthetic approaches (wet chemical deposition, electrodeposition and electrodeposition on chemically preformed Pt nuclei) is employed to shed light on the influence of nanoparticle agglomeration on their electrocatalytic properties. Pt loading on model glassy carbon (GC) support is increased systematically from 1.8 to 10.6 μg Pt cm−2 and changes in the catalyst structure are followed by transmission electron microscopy. At low metal loadings (≤5.4 μg Pt cm−2) isolated single crystalline Pt nanoparticles are formed on the support surface by wet chemical deposition from H2PtCl4 precursor. An increase in the metal loading results, first, in a systematic increase of the average diameter of isolated Pt nanoparticles and, second, in coalescence of nanoparticles and formation of particle agglomerates. This behaviour is in line with the previous observations on carbon-supported noble metal fuel cell electrocatalysts. The catalytic activity of Pt/GC electrodes is tested in CO monolayer oxidation. In agreement with the previous studies (F. Maillard, M. Eikerling, O. V. Cherstiouk, S. Schreier, E. Savinova and U. Stimming, Faraday Discuss., 2004, 125, 357), we find that the reaction is strongly size sensitive, exhibiting an increase of the reaction overpotential as the particle size decreases below ca. 3 nm. At larger particle sizes the dependence levels off, the catalytic activity of particles with diameters above 3 nm approaching that of polycrystalline Pt. Meanwhile, Pt agglomerates show remarkably enhanced catalytic activity in comparison to either isolated Pt nanopraticles or polycrystalline Pt foil, catalysing CO monolayer oxidation at ca. 90 mV lower overpotential. Enhanced catalytic activity of Pt agglomerates is ascribed to high concentration of surface defects. CO stripping voltammograms from Pt/GC electrodes, comprising Pt agglomerates along with isolated single crystalline Pt nanoparticles from 2 to 6 nm size, feature double voltammetric peaks, the more negative corresponding to CO oxidation on Pt agglomerates, while the more positive to CO oxidation on isolated Pt nanoparticles. It is shown that CO stripping voltammetry provides a fingerprint of the particle size distribution and the extent of particle agglomeration in carbon-supported Pt catalysts.