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Schuhmann, Wolfgang

Publications and source records attributed to Schuhmann, Wolfgang.

7 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

A single-Pt-atom-on-Ru-nanoparticle electrocatalyst for CO-resilient methanol oxidation

Single Pt atom catalysts are key targets because a high exposure of Pt substantially enhances electrocatalytic activity. In addition, PtRu alloy nanoparticles are the most active catalysts for the methanol oxidation reaction. To combine the exceptional activity of single Pt atom catalysts with an active Ru support we must overcome the synthetic challenge of forming single Pt atoms on noble metal nanoparticles. In this report we demonstrate a process that grows and spreads Pt islands on Ru branched nanoparticles to create single-Pt-atom-on-Ru catalysts. By following the spreading process by in situ TEM, we found that the formation of a stable single atom structure is thermodynamically driven by the formation of strong Pt–Ru bonds and the lowering of the surface energy of the Pt islands. The stability of the single-Pt-atom-on-Ru structure and its resilience to CO poisoning result in a high current density and mass activity for the methanol oxidation reaction over time.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Elektroenzymatische Stickstofffixierung unter Verwendung eines MoFe‐Proteinsystems immobilisiert in einem organischen Redoxpolymer

Abstract Wir berichten über ein auf einem Polymer basierendes, elektroenzymatisches Stickstofffixierungssystem unter Verwendung eines metallfreien Redoxpolymers – mit Neutralrot modifiziertes Poly(glycidylmethacrylat‐ co ‐methylmethacrylat‐ co ‐poly(ethylenglycol)methacrylat), das ein niedriges Redoxpotential von −0.58 V vs. SCE besitzt. Die stabile und effiziente elektrische Kontaktierung der Nitrogenase innerhalb der Redoxpolymermatrix ermöglicht eine mediierte Bioelektrokatalyse von N 3 − , NO 2 − und N 2 zu NH 3 , die durch das MoFe‐Protein über die polymergebundenen Redoxeinheiten, die in der Polymermatrix verteilt sind, katalysiert wird. Elektrolyse produzierte 209±30 nmol NH 3 nmol MoFe −1 h −1 durch N 2 ‐Reduktion. Die biosynthetische N 2 ‐Reduktion zu NH 3 wurde durch 15 N 2 ‐Markierungsexperimente und NMR‐Analysen bestätigt.

Lee, Yoo Seok↗
DOE OSTI2020

Electroenzymatic Nitrogen Fixation Using a MoFe Protein System Immobilized in an Organic Redox Polymer

Abstract We report an organic redox‐polymer‐based electroenzymatic nitrogen fixation system using a metal‐free redox polymer, namely neutral‐red‐modified poly(glycidyl methacrylate‐ co ‐methylmethacrylate‐ co‐ poly(ethyleneglycol)methacrylate) with a low redox potential of −0.58 V vs. SCE. The stable and efficient electric wiring of nitrogenase within the redox polymer matrix enables mediated bioelectrocatalysis of N 3 − , NO 2 − and N 2 to NH 3 catalyzed by the MoFe protein via the polymer‐bound redox moieties distributed in the polymer matrix in the absence of the Fe protein. Bulk bioelectrosynthetic experiments produced 209±30 nmol NH 3 nmol MoFe −1 h −1 from N 2 reduction. 15 N 2 labeling experiments and NMR analysis were performed to confirm biosynthetic N 2 reduction to NH 3 .

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2020

Facettierte verzweigte Nickel‐Nanopartikel mit variierbarer Verzweigungslänge für die hochaktive elektrokatalytische Oxidation von Biomasse

Abstract Die Kontrolle der Bildung von verzweigten Nanopartikeln mit hoher Homogenität ist eine der größten Herausforderungen bei der Herstellung von Nanokatalysatoren mit verbesserter Aktivität und Stabilität. Mithilfe eines Mechanismus unter Nutzung eines kubischen Kerns und hexagonaler Verzweigung zur Bildung hochgradig monodisperser verzweigter Nanopartikel wurde die Länge der Nickelverzweigungen variiert. Es hat sich gezeigt, dass die Verlängerung der Nickelzweige mit ihrer hohen Bedeckung der aktiven Facetten die Aktivität für die elektrokatalytische Oxidation von 5‐Hydroxymethylfurfural (HMF) als Beispiel für die Umwandlung von Biomasse verbessert.

Poerwoprajitno, Agus R.↗
DOE OSTI2020

Structural and photoelectrochemical properties in the thin film system Cu–Fe–V–O and its ternary subsystems Fe–V–O and Cu–V–O

Thin-film material libraries in the ternary and quaternary metal oxide systems Fe–V–O, Cu–V–O, and Cu–Fe–V–O were synthesized using combinatorial reactive co-sputtering with subsequent annealing in air. Their compositional, structural, and functional properties were assessed using high-throughput characterization methods. Prior to the investigation of the quaternary system Cu–Fe–V–O, the compositions (Fe 61 V 39 )O x and (Cu 52 V 48 )O x with promising photoactivity were identified from their ternary subsystems Fe–V–O and Cu–V–O, respectively. Two Cu–Fe–V–O material libraries with (Cu 29-72 Fe 4-27 V 22-57 )O x and (Cu 11-55 Fe 27-73 V 12-34 )O x composition spread were investigated. Seven mixed ternary and quaternary phase regions were identified: I (α-Cu 3 FeV 6 O 26 /FeVO 4 ), II (Cu 5 V 2 O 10 /FeVO 4 /α-Cu 3 Fe 4 V 6 O 26 ), III (Cu 5 V 2 O 10 ), IV (Cu 5 V 2 O 10 /FeVO 4 , V (FeVO 4 /γ-Cu 2 V 2 O 7 /α-Cu 3 Fe 4 V 6 O 26 ), VI (β-Cu 2 V 2 O 7 /α-Cu 3 Fe 4 V 6 O 26 /FeVO 4 ), and VII (β-Cu 3 Fe 4 V 6 O 26 /FeVO 4 ). Furthermore, in the investigated composition range, two photoactive regions, (Cu 53 Fe 7 V 40 )O x and (Cu 45 Fe 21 V 34 )O x , were identified, exhibiting 103 μ A/cm 2 and 108 μ A/cm 2 photocurrent density for the oxygen evolution reaction at 1.63 V vs reversible hydrogen electrode, respectively. The highest photoactive region (Cu 45 Fe 21 V 34 )O x comprises the dominant α-Cu 3 Fe 4 V 6 O 24 phase and minor FeVO 4 phase. This photoactive region corresponds to having an indirect bandgap of 1.87 eV and a direct bandgap of 2.58 eV with an incident photon-to-current efficiency of 30% at a wavelength of 310 nm.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

High-throughput characterization of Ag–V–O nanostructured thin-film materials libraries for photoelectrochemical solar water splitting

Ag–V–O thin-film materials libraries, with both composition (Ag 22-77 V 23-78 O x ) and thickness (123–714 nm) gradients were fabricated using combinatorial reactive magnetron co-sputtering aiming on establishing relations between composition, structure, and functional properties. As-deposited libraries were annealed in air at 300 °C for 10 h. High-throughput characterization methods of composition, structure and functional properties were used to identify photoelectrochemically active regions. The phases AgV 6 O 15 , Ag 2 V 4 O 11 , AgVO 3 , and Ag 4 V 2 O 7 were observed throughout the composition gradient. The photoelectrochemical properties of Ag–V–O films are dependent on composition and morphology. An enhanced photocurrent density (~300–554 μA/cm 2 ) was obtained at 30 to 45 at.% Ag along the thickness gradient. Thin films of these compositions show a nanowire morphology, which is an important factor for the enhancement of photoelectrochemical performance. The photoelectrochemically active regions were further investigated by high-throughput synchrotron-X-ray diffraction and transmission electron microscopy (Ag 32 V 68 O x ) which confirmed the presence of Ag 2 V 4 O 11 as the dominating phase along with the minor phases AgV 6 O 15 and AgVO 3 . This enhanced photoactive region shows bandgap values of ~2.30 eV for the direct and ~1.87 eV for the indirect bandgap energies. Finally, the porous nanostructured films improve charge transport and are hence of interest for photoelectrochemical water splitting.

36 MATERIALS SCIENCE↗