Demonstration of an AI-driven workflow for dynamic x-ray spectroscopy (supporting data)
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Du, Ming (ORCID:0000000316026646)↗
Engineering topics
Kelly, Shelly D.
Publications and source records attributed to Kelly, Shelly D..
Modifikation eines Cu‐Pd‐Schaufelrad‐Metall‐Organischen Gerüsts für die selektive CO 2 ‐Elektroreduktion
Abstract Die Optimierung der Bindungsenergie zwischen dem Intermediat und dem aktiven Zentrum ist ein entscheidender Faktor, um die katalytische Produktselektivität und Aktivität bei der elektrochemischen Kohlendioxidreduktion (CO 2 RR) zu steuern. Es ist bekannt, dass Kupferatome als aktive Zentren CO 2 zu Kohlenwasserstoffen und Sauerstoffverbindungen reduzieren, jedoch unter schlechter Produktselektivität leiden, da mehrere Intermediate nur moderate Bindungsenergien aufweisen. Hier berichten wir über eine Ionenaustauschstrategie zur Konstruktion von Cu−Pd‐Schaufelrad‐Dimeren innerhalb von Cu‐basierten metallorganischen Gerüsten (MOFs), [Cu 3‐x Pdx(BTC) 2 ] (BTC=1,3,5‐Benzoltricarbonsäure), ohne die strukturellen Eigenschaften des MOFs zu verändern. Im Vergleich zum reinen Cu‐MOF ([Cu 3 (BTC) 2 ], HKUST‐1) verlagert der Cu−Pd‐MOF die Produkte der CO 2 ‐Elektroreduktion von einer Vielzahl chemischer Spezies hin zu einer selektiven CO‐Erzeugung. Eine in situ‐Röntgenabsorptions‐Feinstrukturanalyse der Oxidationsstufe des Katalysators und der lokalen Geometrie, kombiniert mit theoretischen Berechnungen, zeigt, dass die Einfügung von Pd in die Knotenpunkte der Cu‐Schaufelradstruktur des MOFs die Adsorption des Schlüsselintermediats COOH* am Cu‐Zentrum fördert. Dies ermöglicht CO‐selektive katalytische Mechanismen und verbessert somit unser Verständnis über das Zusammenspiel von Struktur und Aktivität bei der elektrochemischen CO 2 ‐Reduktion unter Verwendung molekularer Katalysatoren.
Zhang, Ruirui↗
Engineering a Cu‐Pd Paddle‐Wheel Metal–Organic Framework for Selective CO 2 Electroreduction
Optimizing the binding energy between the intermediate and the active site is a key factor for tuning catalytic product selectivity and activity in the electrochemical carbon dioxide reduction reaction. Copper active sites are known to reduce CO 2 to hydrocarbons and oxygenates, but suffer from poor product selectivity due to the moderate binding energies of several of the reaction intermediates. Here, we report an ion exchange strategy to construct Cu−Pd paddle wheel dimers within Cu-based metal–organic frameworks (MOFs), [Cu 3-x Pd x (BTC) 2 ] (BTC=benzentricarboxylate), without altering the overall MOF structural properties. Compared to the pristine Cu MOF ([Cu 3 (BTC) 2 ], HKUST-1), the Cu−Pd MOF shifts CO 2 electroreduction products from diverse chemical species to selective CO generation. In situ X-ray absorption fine structure analysis of the catalyst oxidation state and local geometry, combined with theoretical calculations, reveal that the incorporation of Pd within the Cu−Pd paddle wheel node structure of the MOF promotes adsorption of the key intermediate COOH* at the Cu site. This permits CO-selective catalytic mechanisms and thus advances our understanding of the interplay between structure and activity toward electrochemical CO 2 reduction using molecular catalysts.
CO2 electroreduction reaction↗
Smaller Is Better: The Case for Lower-Order Iodoplumbate Species Dominating MAPbI 3 /Dimethylformamide Solutions
Here, using complementary experimental measurements and computational predictions of spectroscopic measurements (EXAFS, XANES, and UV–vis), we have determined the identity of the most stable iodoplumbate species in dilute lead halide perovskite precursor solutions. We have determined which species are most likely to be thermodynamically stable compared to others that are unstable or metastable. Condensed phase ab initio models were constructed, and the resulting ensembles were used to directly compare the computed signals to the experimental results of the EXAFS, XANES, and UV–vis spectra of PbI 2 :MAI in DMF. The results of this study suggest that only Pb 2+ , PbI + , and PbI 2 are dominant in the dilute lead perovskite precursor solutions as thermodynamically stable entities. Our interpretation of the relative stability of iodoplumbate species in solution, based on an analysis of EXAFS and XANES spectra, provides critically important new insight into the species most likely to be responsible for crystal nucleation and growth in these materials. This insight will have a significant consequence on the broad scientific community and will necessitate the reinterpretation of peaks in the UV–vis spectra of lead halide perovskite precursor solutions.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Recommendations to standardize reporting, execution, and interpretation of X-ray Absorption Spectroscopy measurements
In July of 2022, a National Science Foundation (NSF)- and US Department of Energy (DOE)-sponsored workshop was held on the topic of rigor and reproducibility (R&R) in thermal, heterogeneous catalysis. As a result of the workshop, a report has been published entitled "Addressing Rigor and Reproducibility in Thermal, Heterogeneous Catalysis"[1]. This manuscript summarizes one section of the report: "Recommendations for catalyst characterization by X-ray absorption spectroscopy". Here, the section focuses exclusively on X-ray absorption spectroscopy (XAS) and is narrowly focused on recommendations for the collection and interpretation of XAS data for routine experiments. Therefore, one should not expect a detailed guide for each different experiment that one may perform nor are the recommendations designed to be overly prescriptive. However, the report is designed to draw attention to key pitfalls and common problems in the collection, reporting, analysis and interpretation of XAS studies.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Advanced X-ray emission spectrometers
Spectroscopy systems require a crystal having specific properties for analyzing a spectrum of a sample, which is typically performed for measuring the presence of one element at a time. A two-dimensional (2D) crystal mount for performing simultaneous spectroscopy measurements includes a crystal holder having multiple rows of crystal mounts. Each crystal mount is positioned and orientated to physically support a crystal at a fixed position and fixed orientation relative to an optical axis. A sample provides radiation to analyzer crystals disposed in the crystal mounts, and a detector may detect radiation reflected from the analyzer crystals, for performing multiple simultaneous spectroscopy measurements.
Sun, Chengjun↗
The AXEAP2 program for K β X-ray emission spectra analysis using artificial intelligence
The processing and analysis of synchrotron data can be a complex task, requiring specialized expertise and knowledge. Our previous work addressed the challenge of X-ray emission spectrum (XES) data processing by developing a standalone application using unsupervised machine learning. However, the task of analyzing the processed spectra remains another challenge. Although the non-resonant K β XES of 3 d transition metals are known to provide electronic structure information such as oxidation and spin state, finding appropriate parameters to match experimental data is a time-consuming and labor-intensive process. Here, a new XES data analysis method based on the genetic algorithm is demonstrated, applying it to Mn, Co and Ni oxides. This approach is also implemented as a standalone application, Argonne X-ray Emission Analysis 2 ( AXEAP2 ), which finds a set of parameters that result in a high-quality fit of the experimental spectrum with minimal intervention. AXEAP2 is able to find a set of parameters that reproduce the experimental spectrum, and provide insights into the 3 d electron spin state, 3 d –3 p electron exchange force and K β emission core-hole lifetime.
36 MATERIALS SCIENCE↗