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Instruments / Technical Area	Publication Details	Published
I20-Scanning-X-ray spectroscopy (XAS/XES)	Impact of single-pulse, low-intensity laser post-processing on structure and activity of mesostructured cobalt oxide for the oxygen evolution reaction Eko Budiyanto , Swen Zerebecki , Claudia Weidenthaler , Tim Kox , Stephane Kenmoe , Eckhard Spohr , Serena Debeer , Olaf Rudiger , Sven Reichenberger , Stephan Barcikowski , Harun Tuysuz Acs Applied Materials & Interfaces DOI: 10.1021/acsami.1c08034 Diamond Proposal Number(s): [25636] Open Access Show Abstract ▼ Abstract: Herein, we report nanosecond, single-pulse laser post-processing (PLPP) in a liquid flat jet with precise control of the applied laser intensity to tune structure, defect sites, and the oxygen evolution reaction (OER) activity of mesostructured Co3O4. High-resolution X-ray diffraction (XRD), Raman, and X-ray photoelectron spectroscopy (XPS) are consistent with the formation of cobalt vacancies at tetrahedral sites and an increase in the lattice parameter of Co3O4 after the laser treatment. X-ray absorption spectroscopy (XAS) and X-ray emission spectroscopy (XES) further reveal increased disorder in the structure and a slight decrease in the average oxidation state of the cobalt oxide. Molecular dynamics simulation confirms the surface restructuring upon laser post-treatment on Co3O4. Importantly, the defect-induced PLPP was shown to lower the charge transfer resistance and boost the oxygen evolution activity of Co3O4. For the optimized sample, a 2-fold increment of current density at 1.7 V vs RHE is obtained and the overpotential at 10 mA/cm2 decreases remarkably from 405 to 357 mV compared to pristine Co3O4. Post-mortem characterization reveals that the material retains its activity, morphology, and phase structure after a prolonged stability test.	Jul 2021
I15-1-X-ray Pair Distribution Function (XPDF)	Monitoring the structure evolution of titanium oxide photocatalysts: From the molecular form via the amorphous state to the crystalline phase Ezgi Onur Sahin , Yitao Dai , Candace Chan , Harun Tuysuz , Wolfgang Schmidt , Joohyun Lim , Siyuan Zhang , Cristina Scheu , Claudia Weidenthaler Chemistry – A European Journal DOI: 10.1002/chem.202101117 Diamond Proposal Number(s): [12102] Show Abstract ▼ Abstract: Amorphous TixOy with high surface area has attracted significant interest as photocatalyst with higher activity in ultraviolet (UV) light-induced water splitting applications compared to commercial nanocrystalline TiO2. Under photocatalytic operation conditions, the structure of the molecular titanium alkoxide precursor rearranges upon hydrolysis and leads to higher connectivity of the structure-building units. Structurally ordered domains with sizes smaller than 7 Å form larger aggregates. The experimental scattering data can be explained best with a structure model consisting of an anatase-like core and a distorted shell. Upon exposure with UV light, the white TixOy suspension turns dark corresponding to the reduction of Ti 4+ to Ti 3+ as confirmed by electron energy loss spectroscopy (EELS). Heat-induced crystallisation was followed by in situ temperature-dependent total scattering experiments. First, ordering in the Ti-O environment takes place upon to 350 °C. Above this temperature, the distorted anatase core starts to grow but the structure obtained at 400 °C is still not fully ordered.	Jun 2021
I15-1-X-ray Pair Distribution Function (XPDF)	In situ total scattering experiments of nucleation and crystallisation of tantalum-based oxides: from highly dilute solutions via cluster formation to nanoparticles Ezgi Onur Sahin , Harun Tueysuez , Candace K. Chan , Gun-Hee Moon , Yitao Dai , Wolfgang Schmidt , Joohun Lim , Christina Scheu , Claudia Weidenthaler Nanoscale DOI: 10.1039/D0NR07871A Diamond Proposal Number(s): [16372] Open Access Show Abstract ▼ Abstract: The exact formation mechanism of tantalum oxides (and in general, metal/mixed metal oxides) from alkoxide precursors is still not fully understood, particularly when forming cluster-like or amorphous materials. The structural evolution of Ta-based oxides was studied in detail using X-ray total scattering experiments along with subsequent pair distribution function (PDF) analyses. Starting from a tantalum alkoxide precursor (Ta2(OEt)10), the formation of hydrolysed TaxOyHz clusters in highly diluted aqueous solution was analysed. From the PDF data, the connectivity and arrangement of TaxOy octahedra in the cluster could be deduced as well as the approximate size of the clusters (<1 nm). Construction of cluster models allowed for identification of common structural motifs in the TaxOyHz clusters, ruling out the formation of chain- or ring-like clusters. More likely, bulky clusters with a high number of corner-sharing octahedra are formed. After separation of the amorphous solid from the liquid, temperature-induced crystallisation processes were monitored via in situ total scattering experiments. Between room temperature and 600 °C, only small rearrangements of the amorphous structure are observed. At about 610 °C, amorphous TaxOyHz transforms directly into crystalline orthorhombic L-Ta2O5 without formation of any crystalline intermediate structures.	Nov 2020
I15-Extreme Conditions	Monitoring the formation of PtNi nanoalloys supported on hollow graphitic spheres using in situ pair distribution function analysis S. Ortatatli , J. Knossalla , F. Schüth , C. Weidenthaler Physical Chemistry Chemical Physics 14 DOI: 10.1039/C7CP07840D Diamond Proposal Number(s): [14028] Open Access Show Abstract ▼ Abstract: This article aims to address the formation and the structural disordering/ordering phenomena of PtNi nanoalloys supported on hollow graphitic spheres (HGSs) using pair distribution function (PDF) analysis under ex situ/in situ data collection conditions. Starting from small nanoparticles (10–15 Å in diameter) embedded in HGSs, structural changes were monitored during stepwise heating and cooling of the sample using in situ PDF analysis. In order to evaluate the conventional synthesis route for the production of PtNi nanoalloys supported on HGSs, ex situ PDF experiments were performed before and after heat treatment in a furnace. The studies demonstrate that the local structure of the in situ synthesised PtNi nanoalloy differs from its ex situ synthesised counterpart. A partially ordered PtNi nanoalloy was obtained during the stepwise in situ cooling of the precursor, whereas the conventional ex situ synthesis route did not lead to the formation of an ordered crystal structure. In this study we could show that rapid heating and cooling results in a disordered PtNi alloy whereas slow heating and cooling leads to disorder–order transitions in PtNi.	Jan 2018

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