Prospects of Heterogeneous Hydroformylation with Supported Single Atom Catalysts

[EN] The potential of oxide-supported rhodium single atom catalysts (SACs) for heterogeneous hydroformylation was investigated both theoretically and experimentally. Using high-level domain-based local-pair natural orbital coupled cluster singles doubles with perturbative triples contribution (DLPNO-CCSD(T)) calculations, both stability and catalytic activity were investigated for Rh single atoms on different oxide surfaces. Atomically dispersed, supported Rh catalysts were synthesized on MgO and CeO2. While the CeO2-supported rhodium catalyst is found to be highly active, this is not the case for MgO, most likely due to increased confinement, as determined by extended X-ray absorption fine structure spectroscopy (EXAFS), that diminishes the reactivity of Rh complexes on MgO. This agrees well with our computational investigation, where we find that rhodium carbonyl hydride complexes on flat oxide surfaces such as CeO2(111) have catalytic activities comparable to those of molecular complexes. For a step edge on a MgO(301) surface, however, calculations show a significantly reduced catalytic activity. At the same time, calculations predict that stronger adsorption at the higher coordinated adsorption site leads to a more stable catalyst. Keeping the balance between stability and activity appears to be the main challenge for oxide supported Rh hydroformylation catalysts. In addition to the chemical bonding between rhodium complex and support, the confinement experienced by the active site plays an important role for the catalytic activity.X-ray absorption experiments were performed at the ALBA Synchrotron Light Source (Spain), experiment 2019023278. Beamline scientists L. Simonelli and C. Marini are gratefully acknowledged for their contribution to beam setup. E. Andrés, E. Martínez-Monje, I. López, and M. García-Farpón (ITQ) are acknowledged for their assistance with XAS data acquisition. J. Ternedien (MPI-KOFO) is acknowledged for the performance of XRD experiments. N. Pfänder (MPI-CEC) is acknowledged for his contribution to STEM characterization. The authors acknowledge support by the state of Baden-Württemberg through bwHPC (bwUnicluster and JUSTUS, RV bw17D01). The authors gratefully acknowledge support by the GRK 2450. Financial support from the Helmholtz Association is also gratefully acknowledged. The experimental work received funding from the Max Planck Society and the Spanish Ministry of Science, Innovation and Universities (projects SEV-2016-0683 and RTI2018-096399-A-I00). B.B.S. acknowledges the Alexander von Humboldt Foundation for a postdoctoral scholarship.Amsler, J.; Sarma, BB.; Agostini, G.; Prieto González, G.; Plessow, P.; Studt, F. (2020). 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Metal-Specific Reactivity in Single-Atom Catalysts: CO Oxidation on 4d and 5d Transition Metals Atomically Dispersed on MgO

Understanding and tuning the catalytic properties of metals atomically dispersed on oxides are major stepping-stones toward a rational development of single-atom catalysts (SACs). Beyond individual showcase studies, the design and synthesis of structurally regular series of SACs opens the door to systematic experimental investigations of performance as a function of metal identity. Herein, a series of single-atom catalysts based on various 4d (Ru, Rh, Pd) and 5d (Ir, Pt) transition metals has been synthesized on a common MgO carrier. Complementary experimental (X-ray absorption spectroscopy) and theoretical (Density Functional Theory) studies reveal that, regardless of the metal identity, metal cations occupy preferably octahedral coordination MgO lattice positions under step-edges, hence highly confined by the oxide support. Upon exposure to O2-lean CO oxidation conditions, FTIR spectroscopy indicates the partial deconfinement of the monatomic metal centers driven by CO at precatalysis temperatures, followed by the development of surface carbonate species under steady-state conditions. These findings are supported by DFT calculations, which show the driving force and final structure for the surface metal protrusion to be metal-dependent, but point to an equivalent octahedral-coordinated M4+ carbonate species as the resting state in all cases. Experimentally, apparent reaction activation energies in the range of 96 ± 19 kJ/mol are determined, with Pt leading to the lowest energy barrier. The results indicate that, for monatomic sites in SACs, differences in CO oxidation reactivity enforceable via metal selection are of lower magnitude than those evidenced previously through the mechanistic involvement of adjacent redox centers on the oxide carrier, suggesting that tuning of the oxide surface chemistry is as relevant as the selection of the supported metal

Overlapping and dissociable brain activations for fluid intelligence and executive functions

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It is debated whether cognitive training of specific executive functions leads to far transfer effects, such as improvements in fluid intelligence (Gf). Within this context, transcranial direct current stimulation and recently also novel protocols such as transcranial random noise and alternating current stimulation are being investigated with regards to their ability to enhance cognitive training outcomes. We compared the effects of four different transcranial electrical brain stimulation protocols in combination with nine daily computerized training sessions on Gf. 82 participants were randomly assigned to receive transcranial direct current stimulation (tDCS), random noise stimulation (tRNS), multifocal alternating current stimulation at 40 Hz (mftACS), or multifocal tDCS (mftDCS) in combination with an adaptive and synergistic executive function (EF) training, or to a no-contact control group. EF training consisted of gamified tasks drawing on isolated as well as integrated executive functions (working memory, inhibition, cognitive flexibility). Transfer was assessed with a combined measure of Gf including three established tests (Bochumer Matrizentest - BOMAT, Raven's Advanced Progressive Matrices - RAPM, and Sandia Matrices). We found significant improvements in Gf for the tDCS, mftDCS, and tRNS groups when compared with the no-contact group. In contrast, the mftACS group did not improve significantly and showed a similar pattern as the no-contact group. Mediation analyses indicated that the improvement in Gf was mediated through game progression in the mftDCS and tRNS group. Electrical brain stimulation in combination with sustained EF training can lead to transfer effects in Gf, which are mediated by training progression

Ginseng and ginkgo biloba effects on cognition as modulated by cardiovascular reactivity: a randomised trial

Background There is some evidence to suggest that ginseng and Ginkgo biloba can improve cognitive performance, however, very little is known about the mechanisms associated with such improvement. Here, we tested whether cardiovascular reactivity to a task is associated with cognitive improvement. Methodology/Principal findings Using a double-blind, placebo controlled, crossover design, participants (N = 24) received two doses of Panax Ginseng (500, 1000 mg) or Ginkgo Biloba (120, 240 mg) (N = 24), and underwent a series of cognitive tests while systolic, diastolic, and heart rate readings were taken. Ginkgo Biloba improved aspects of executive functioning (Stroop and Berg tasks) in females but not in males. Ginseng had no effect on cognition. Ginkgo biloba in females reversed the initial (i.e. placebo) increase in cardiovascular reactivity (systolic and diastolic readings increased compared to baseline) to cognitive tasks. This effect (reversal) was most notable after those tasks (Stroop and Iowa) that elicited the greatest cardiovascular reactivity during placebo. In males, although ginkgo also decreased cardiovascular readings, it did so from an initial (placebo) blunted response (i.e. decrease or no change from baseline) to cognitive tasks. Ginseng, on the contrary, increased cardiovascular readings compared to placebo. Conclusions/Significance These results suggest that cardiovascular reactivity may be a mechanism by which ginkgo but not ginseng, in females is associated with certain forms of cognitive improvement

GRDC-Caravan: extending Caravan with data from the Global Runoff Data Centre

Large-sample datasets are essential in hydrological science to support modelling studies and advance process understanding. Here, we present the GRDC-Caravan dataset, an extension to the large-sample hydrology project Caravan. Caravan is a community initiative which aims to combine large-sample hydrology datasets of meteorological forcing data, catchment attributes and discharge data for catchments around the world. The GRDC-Caravan extension is based on a subset of hydrological discharge data and station-based watersheds from the Global Runoff Data Centre (GRDC), which are covered by an open data policy. The GRDC is an international data centre operating under the auspices of the World Meteorological Organization (WMO), which collects quality-controlled river discharge data and associated metadata from the National Meteorological and Hydrological Services (NMHS) of WMO member states. The extension contains discharge data and catchment boundaries from GRDC, which can be released under a permissive license (CC-BY-4.0). In addition, the extension contains meteorological forcing data and catchment attributes from the global datasets ERA5-Land and HydroATLAS in a standardized format. The dataset covers stations from 5356 catchments and 25 countries and spans the years 1950–2023. Compared to the core version of Caravan, the extension takes the total number of Caravan catchments to be 22 372 (of which 1589 catchments are duplicates between the core and extensions). While in the core Caravan dataset mostly stations from North America, central Europe and South America were included, the new extension significantly improves the global coverage of the dataset with new stations across Europe, South America, South Africa, Australia and Aotearoa New Zealand. In addition, the temporal extension of the time series could be significantly increased from 40–70 years. The extension strongly improves the global and temporal coverage of Caravan and represents a valuable dataset for global hydrological and climatological modelling studies. The dataset is released under a CC-BY-4.0 license that allows for redistribution and is publicly available on Zenodo: https://doi.org/10.5281/zenodo.15349031 (Färber et al., 2025).</p

Sustainable land-use alternatives in tropical rainforests? Evidence from natural and social sciences.

The Amazon rainforest, formerly pristine and highly biodiverse, is increasingly under threat from deforestation for cattle grazing, other forms of agriculture, mining and development. To better understand which land management type best serves sustainability aims, we compare soil gas exchange (CO2, CH4, N2O) and soil chemistry for forested land with post-forest land at 13 locations and 29 sites within the state of Amazonas, Brazil. We find that forest soils show distinctively different signals and signatures compared to soils in post-forest land use cases. Crucial answers emerge regarding the limits of system resilience as well as sustainable alternatives to deforestation and current land-use practices. We carry out a socioeconomic evaluation and discuss the likely reasons for inaction and how to overcome them