Structure and Reactivity of Model CeO2surfaces

As a key component in many industrial heterogeneous catalysts, the surface structure and reactivity of ceria, CeO2, has attracted a lot of attention. In this topical review we discuss some of the approaches taken to form a deeper understanding of the surface physics and chemistry of this important and interesting material. In particular, we focus on the preparation of ultrathin ceria films, nanostructures and supported metal nanoparticles. Cutting-edge microscopic and spectroscopic experimental techniques are highlighted which can probe the behaviour of oxygen species and atomic defects on these model surfaces

Role of salt concentration in stabilizing charged Ni-rich cathode interfaces in Li-ion batteries

The cathode–electrolyte interphase (CEI) in Li-ion batteries plays a key role in suppressing undesired side reactions while facilitating Li-ion transport. Ni-rich layered cathode materials offer improved energy densities, but their high interfacial reactivities can negatively impact the cycle life and rate performance. Here we investigate the role of electrolyte salt concentration, specifically LiPF6 (0.5–5 m), in altering the interfacial reactivity of charged LiN0.8Mn0.1Co0.1O2 (NMC811) cathodes in standard carbonate-based electrolytes (EC/EMC vol %/vol % 3:7). Extended potential holds of NMC811/Li4Ti5O12 (LTO) cells reveal that the parasitic electrolyte oxidation currents observed are strongly dependent on the electrolyte salt concentration. X-ray photoelectron and absorption spectroscopy (XPS/XAS) reveal that a thicker LixPOyFz-/LiF-rich CEI is formed in the higher concentration electrolytes. This suppresses reactions with solvent molecules resulting in a thinner, or less-dense, reduced surface layer (RSL) with lower charge transfer resistance and lower oxidation currents at high potentials. The thicker CEI also limits access of acidic species to the RSL suppressing transition-metal dissolution into the electrolyte, as confirmed by nuclear magnetic resonance (NMR) spectroscopy and inductively coupled plasma optical emission spectroscopy (ICP-OES). This provides insight into the main degradation processes occurring at Ni-rich cathode interfaces in contact with carbonate-based electrolytes and how electrolyte formulation can help to mitigate these

Direct Conversion of Methane to Methanol on Ni-Ceria Surfaces: Metal-Support Interactions and Water-Enabled Catalytic Conversion by Site Blocking

[EN] The transformation of methane into methanol or higher alcohols at moderate temperature and pressure conditions is of great environmental interest and remains a challenge despite many efforts. Extended surfaces of metallic nickel are inactive for a direct CH → CHOH conversion. This experimental and computational study provides clear evidence that low Ni loadings on a CeO(111) support can perform a direct catalytic cycle for the generation of methanol at low temperature using oxygen and water as reactants, with a higher selectivity than ever reported for ceria-based catalysts. On the basis of ambient pressure X-ray photoemission spectroscopy and density functional theory calculations, we demonstrate that water plays a crucial role in blocking catalyst sites where methyl species could fully decompose, an essential factor for diminishing the production of CO and CO, and in generating sites on which methoxy species and ultimately methanol can form. In addition to water-site blocking, one needs the effects of metal-support interactions to bind and activate methane and water. These findings should be considered when designing metal/oxide catalysts for converting methane to value-added chemicals and fuels.The work carried out at Brookhaven National Laboratory was supported by the U.S. Department of Energy (Chemical Sciences Division, DE-SC0012704). S.D.S. is supported by a U.S. Department of Energy Early Career Award. This research used resources of the Advanced Light Source (Beamline 9.3.2),which is a DOE Office of Science User Facility under contract no. DE-AC02-05CH11231. Authors acknowledge contribution of Dr. Ethan Crumlin for assistance with AP-XPS measurements. M.V.G.-P. acknowledges the financial support of the /Ministry of Economy and Competitiveness MINECO-Spain (Grant No. CTQ2015-78823-R) and P.G.L. that of the Agencia Nacional de Promocion Científiica y Tecnologica-Argentina (Grant No. PICT-2016-2750). Computer time provided by the BIFI-ZCAM, RES at the Marenostrum and La Palma nodes, SNCAD (Sistema Nacional de Computación de Alto Desempeño, Argentina), and the DECI resources BEM based in Poland at WCSS and Archer at EPCC with support from the PRACE aislb, is acknowledged. M.V. thanks the Ministry of Education, Youth and Sports of the Czech Republic for financial support under Project LH15277. R.M.P. was partially funded by the AGEP-T (Alliance for Graduate Education and the Professoriate−Transformation) which is funded by the National Science Foundation, award #131131

The relationship between sensory sensitivity and autistic traits in the general population.

Individuals with Autism Spectrum Disorders (ASDs) tend to have sensory processing difficulties (Baranek et al. in J Child Psychol Psychiatry 47:591–601, 2006). These difficulties include over- and under-responsiveness to sensory stimuli, and problems modulating sensory input (Ben-Sasson et al. in J Autism Dev Disorders 39:1–11, 2009). As those with ASD exist at the extreme end of a continuum of autistic traits that is also evident in the general population, we investigated the link between ASD and sensory sensitivity in the general population by administering two questionnaires online to 212 adult participants. Results showed a highly significant positive correlation (r = .775, p < .001) between number of autistic traits and the frequency of sensory processing problems. These data suggest a strong link between sensory processing and autistic traits in the general population, which in turn potentially implicates sensory processing problems in social interaction difficulties

Fabrication of Isolated Iron Nanowires

Nanoscale interconnects are an important component of molecular electronics. Here we use X-ray spectromicroscopy techniques as well as scanning probe methods to explore the self-assembled growth of insulated iron nanowires as a potential means of supplying an earth abundant solution. The intrinsic anisotropy of a TiO2(110) substrate directs the growth of micron length iron wires at elevated temperatures, with a strong metal-support interaction giving rise to ilmenite (FeTiO3) encapsulation. Iron nanoparticles that decorate the nanowires display magnetic properties that suggest other possible applications

Adsorption structure of iron phthalocyanine and titanyl phthalocyanine on Cu(1 1 1)

The adsorption structure of iron phthalocyanine (FePc) and titanyl phthalocyanine (TiOPc) was studied by a combination of near edge X-ray absorption fine structure (NEXAFS) spectroscopy and normal incidence X-ray standing waves (NIXSW) technique. The FePc results demonstrate that the molecule adsorbs with the Fe metal centre at an adsorption height of 2.44 ± 0.09 Å, its macrocycle plane mostly parallel with the underlying surface and a single adsorption configuration. However, a small distortion of the isoindole groups, with respect to one another, is required to rationalise the results. The TiOPc results similarly indicate that the macrocycle plane is mostly parallel with the underlying surface up to thick multilayer films, yet, in the monolayer regime, the molecule must adsorb in multiple configurations. These configurations are nominally assigned to a mixture of adsorption configurations with some Ti=O bonds pointing towards the surface, and some pointing away. We determine that, in both configurations, the Ti metal centre sits at a similar adsorption height above the surface of 3.00 ± 0.20 Å

Spectroscopic identification of active sites of oxygen-doped carbon for selective oxygen reduction to hydrogen peroxide

The electrochemical synthesis of hydrogen peroxide (H2O2) via a two-electron (2 e−) oxygen reduction reaction (ORR) process provides a promising alternative to replace the energy-intensive anthraquinone process. Herein, we develop a facile template-protected strategy to synthesize a highly active quinone-rich porous carbon catalyst for H2O2 electrochemical production. The optimized PCC900 material exhibits remarkable activity and selectivity, of which the onset potential reaches 0.83 V vs. reversible hydrogen electrode in 0.1 M KOH and the H2O2 selectivity is over 95 % in a wide potential range. Comprehensive synchrotron-based near-edge X-ray absorption fine structure (NEXAFS) spectroscopy combined with electrocatalytic characterizations reveals the positive correlation between quinone content and 2 e− ORR performance. The effectiveness of chair-form quinone groups as the most efficient active sites is highlighted by the molecule-mimic strategy and theoretical analysis

Spectroscopic Identification of Active Sites of Oxygen-Doped Carbon for Selective Oxygen Reduction to Hydrogen Peroxide

The electrochemical synthesis of hydrogen peroxide (H2O2) via a two-electron (2 e−) oxygen reduction reaction (ORR) process provides a promising alternative to replace the energy-intensive anthraquinone process. Herein, we develop a facile template-protected strategy to synthesize a highly active quinone-rich porous carbon catalyst for H2O2 electrochemical production. The optimized PCC900 material exhibits remarkable activity and selectivity, of which the onset potential reaches 0.83 V vs. reversible hydrogen electrode in 0.1 M KOH and the H2O2 selectivity is over 95 % in a wide potential range. Comprehensive synchrotron-based near-edge X-ray absorption fine structure (NEXAFS) spectroscopy combined with electrocatalytic characterizations reveals the positive correlation between quinone content and 2 e− ORR performance. The effectiveness of chair-form quinone groups as the most efficient active sites is highlighted by the molecule-mimic strategy and theoretical analysis

Fabrication of isolated iron nanowires

Nanoscale interconnects are an important component of molecular electronics. Here we use X-ray spectromicroscopy techniques as well as scanning probe methods to explore the self-assembled growth of insulated iron nanowires as a potential means of supplying an earth abundant solution. The intrinsic anisotropy of a TiO2(110) substrate directs the growth of micron length iron wires at elevated temperatures, with a strong metal–support interaction giving rise to ilmenite (FeTiO3) encapsulation. Iron nanoparticles that decorate the nanowires display magnetic properties that suggest other possible applications