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Results for “Cuprous oxide”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Cryogenic Carbon Monoxide Oxidation on Cuprous Oxide

Performing oxidation reactions at low temperatures using earth-abundant materials is crucial for advancing solutions for sustainable chemistry. CO oxidation serves as a benchmark reaction to characterize oxidation and to advance fundamental concepts in surface chemistry. While there are several examples of CO oxidation occurring on metal oxides at low temperatures, from 300 K to ∼200 K, reactivity in the cryogenic temperature regime typically requires a metal nanoparticle on a metal oxide. Here, we show oxygen atoms on the (111) facet of Cu 2 O react with CO to form CO 2 at temperatures below 100 K. Combining spectroscopic experimental evidence with calculations, we propose a low barrier path for CO oxidation at reconstructed surface sites on Cu 2 O(111). This finding is a rare example of an earth-abundant metal oxide, in this case copper, that can provide highly reactive multifunctional sites, enabling both adsorption and reaction fundamental steps toward the efficient heterogeneous oxidation of chemicals.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Photoelectrochemical Nitrogen Reduction to Ammonia on Cupric and Cuprous Oxide Photocathodes

Photoelectrochemical N 2 reduction enables the production of NH 3 under ambient conditions using water as the hydrogen source. Furthermore, by utilizing solar energy, photoelectrochemical N 2 reduction can significantly reduce the energy input required for N 2 reduction. In this study, photoelectrochemical N 2 production was investigated using CuO and Cu 2 O photocathodes that are known to be poorly catalytic for water reduction, the major reaction competing with N 2 reduction. When tested under simulated solar illumination with isotopically labeled 15 N 2 in 0.1 M KOH solution, the CuO and Cu 2 O photocathodes produced 15 NH 3 with a Faradaic efficiency of 17% and 20% at 0.6 V and 0.4 V vs. RHE, respectively. These potentials are significantly more positive than the thermodynamic reduction potential of N 2 , which demonstrates how the use of photoexcited electrons in the CuO and Cu 2 O photocathodes can reduce the energy input required for NH 3 production. Here, the use of photoexcited electrons in these photocathodes for N 2 reduction, water reduction, and photocorrosion was carefully examined.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Enhanced Oxide Reduction by Hydrogen at Cuprous Oxide–Copper Interfaces near Ascending Step Edges

We report that understanding the dynamic processes involved in the interaction of hydrogen with oxides is of fundamental importance in catalysis. This paper probes the reduction of Cu 2 O-‘29’ surfaces by hydrogen at room temperature combining in situ ambient pressure scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations. Reduction of the atomic layer thin Cu 2 O film is observed to be preferentially initiated2 at step edges and terrace defects, where perfect Cu 2 O(111) terraces are found to be stable towards hydrogenation under the same conditions. After a long induction period, regions of partially reduced Cu 2 O-‘29’ and metallic Cu co-exist before the surface is fully reduced to Cu(111). The reduction rate strongly depends on the nature of nearby Cu step edges. We propose a mechanism for the reduction of Cu 2 O-‘29’ by hydrogen where free copper atoms from ascending metallic step edges facilitate the formation of active ensembles for H 2 dissociation and transfer H to the edges of Cu2O regions

08 HYDROGEN↗
DOE OSTI2025

Bottom-up fabrication of 2D Rydberg exciton arrays in cuprous oxide

Solid-state platforms provide exceptional opportunities for advancing on-chip quantum technologies by enhancing interaction strengths through coupling, scalability, and robustness. Cuprous oxide (Cu 2 O) has recently emerged as a promising medium for scalable quantum technology due to its high-lying Rydberg excitonic states, akin to those in hydrogen atoms. To harness these nonlinearities for quantum applications, the confinement dimensions must match the Rydberg blockade size, which can reach several microns in Cu 2 O. Using a CMOS-compatible growth technique, this study demonstrates the bottom-up fabrication of site-selective arrays of Cu 2 O microparticles. We observed Rydberg excitons up to the principal quantum number n = 5 within these Cu 2 O arrays on a quartz substrate and analyzed the spatial variation of their spectrum across the array, showing robustness and reproducibility on a large chip. These results lay the groundwork for the deterministic growth of Cu 2 O around photonic structures, enabling substantial light-matter interaction on integrated photonic platforms and paving the way for scalable, on-chip quantum devices.

36 MATERIALS SCIENCE↗
DOE OSTI2024

The surface chemistry of cuprous oxide

The chemical and electronic properties of copper combined with its large natural abundance lend this material to impact a wide range of technological applications, including heterogeneous catalysis. The reactivity of copper in its Cu 1+ oxidation state makes this specific configuration relevant in various chemical reactions, but the facile redox properties of copper make the isolation of individual states for fundamental studies difficult. Here, in this study, we review three Cu 2 O model systems used to study the interaction of Cu 1+ with small molecules making use of surface science techniques: Cu 2 O/Cu(111), thin polycrystalline Cu 2 O films on Cu foil, and bulk Cu 2 O crystals. Advantages and disadvantages of each system are discussed and exemplified through case studies of chemical adsorption and reactivity studies.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Vapor–Fed Electrolyzers for Carbon Dioxide Reduction Using Tandem Electrocatalysts: Cuprous Oxide Coupled with Nickel–Coordinated Nitrogen–Doped Carbon

We report ethylene is particularly attractive due to its major importance as a feedstock for various applications including the polymer industry. As such, catalyst and electrolyzer developments are crucial to achieve industrially relevant ethylene production and efficiency levels. In this work, a tandem electrocatalyst composed of copper nanocubes and nickel-coordinated nitrogen-doped carbon (NiNC) is presented, which is integrated into gas diffusion electrodes (GDEs) for direct conversion of vapor-fed CO 2 into ethylene. Evaluation of tandem GDEs in the vapor-fed flow electrolyzer shows significantly increased ethylene selectivity in terms of faradaic efficiency and C 2 H 4 /CO ratio compared to a non-tandem copper GDE. The enhancements are attributed to the increased local CO availability near the copper surface via effective CO 2 to CO conversion on neighboring NiNC. The experimental results are validated by 3D resolved continuum simulations, which show increased flux of higher-order prod-ucts with the added CO flux from NiNC. The practical viability of Cu/NiNC catalyst is further evaluated in a membrane electrode assembly electrolyzer, achieving 40% FE toward ethylene at 150 mA cm -2 and 3.2 V. These find-ings highlight the high selectivity and formation rate of ethylene achieved by successful device integration of the Cu/NiNC catalyst, demonstrating the potential for implementation in large-scale sustainable CO 2 electrolyzers.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Surface modification induced cuprous oxide nanoparticle toxicity to duckweed at sub-toxic metal concentrations

Nanoparticle capping agents are critical for controlling the growth, oxidation state, and final particle size during aqueous synthesis. However, despite the known phytotoxicity of cetyltrimethylammonium bromide (CTAB) to plants, it is used to synthesize metal oxide nanoparticles of uniform size and with mesoporous structure. Among the few studies that have investigated how CTAB influences nanoparticle toxicity, CTAB has never been identified as the primary cause of nanoparticle toxicity in environmental systems; rather nanoparticle surface charge or morphology was identified as the driver of toxicity in environmentally relevant systems. In the current study, CTAB release from CTAB surface modified Cu 2 O nanoparticles (SM-Cu 2 O NPs) inhibited duckweed (Landoltia punctata) growth, even when administered at subtoxic Cu concentrations. Organic ligands, such as humic acid (HA) and ethylenediaminetetraacetic acid (EDTA), lessened growth inhibition associated with exposure to SM-Cu 2 O NPs, likely through electrostatic and hydrophobic interactions with CTAB. Finally, such results highlight the need for a more holistic approach to nanoparticle surface modification and improved communication between toxicologists and synthetic chemists to develop green alternatives for nanoparticle synthesis.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Effect of ZnO and PEDOT:PSS charge selective layers on photovoltage of cuprous oxide (Cu 2 O) heterojunction solar cells

Electrochemical deposition (ECD) of Cu 2 O provides a scalable and low temperature pathway to solar cells with a theoretical high energy conversion efficiency of 23%, based on the 2.0–2.2 eV band gap of Cu 2 O. However, existing ECD-Cu 2 O devices are plagued by poor crystallinity and low selectivity of the electron and hole transport layers. Here we use Vibrating Kelvin Probe Surface Photovoltage Spectroscopy (VKP-SPV) to probe the charge transfer selectivity in FTO/ZnO/Cu 2 O/PEDOT:PSS/Ni heterojunction solar cells. Selective electron extraction is achieved at the ZnO back contact to Cu 2 O, as confirmed by a negative surface photovoltage signal. While the uncoated Cu 2 O surface is electron-selective due to the formation of a hole depletion layer, spin coating of a PEDOT:PSS film turns it into a hole-selective interface. After adding nickel metal ink top electrodes, functional 1.0 cm 2 solar cells with power conversion efficiency (PCE) of up to 0.07%, 195 mV open-circuit voltage, and 1.28 mA cm –2 short-circuit photocurrent are achieved. The photovoltaic performance is higher for aluminum doped zinc oxide (AZO) substrates than for fluorine doped tin oxide (FTO) due to the presence of a n-/p-junction that further increases the electron selectivity of the AZO/ZnO/Cu 2 O contacts. Overall, this work demonstrates the first application of PEDOT:PSS as a hole transport layer (HTL) for Cu 2 O and the use of VKP-SPV to measure the photovoltage contributions of the Cu 2 O interfaces. Furthermore, the ability to fabricate Cu 2 O solar cells at near room temperature without the use of vacuum methods or rare elements is an important step towards a scalable Cu 2 O PV technology.

14 SOLAR ENERGY↗
DOE OSTI2022

Stability of Polyethylene Glycol-Coated Copper Nanoparticles and Their Optical Properties

Oxidation is a corrosion reaction where the corroded metal forms an oxide. Prevention of oxidation at the nanoscale is critically important to retain the physicochemical properties of metal nanoparticles. In this work, we studied the stability of polyethylene glycol (PEG) coated copper nanoparticles (PEGylated CuNPs) against oxidation. The freshly-prepared PEGylated CuNPs mainly consist of metallic Cu which are quite stable in air although their surfaces are typically covered with a few monolayers of cuprous oxide. However, they are quickly oxidized in water due to the presence of protons that facilitate oxidation of the cuprous oxide to cupric oxide. PEG with carboxylic acid terminus could slightly delay the oxidation process compared to that with thiol terminus. It was found that a solvent with reducing power such as ethanol could greatly enhance the stability of PEGylated CuNPs by preventing further oxidation of the cuprous oxide to cupric oxide and thus retain the optical properties of CuNPs. The reducing environment also assists the galvanic replacement of these PEGylated CuNPs to form hollow nanoshells; however, they consist of ultra-small particle assemblies due to the co-reduction of gold precursor during the replacement reaction. As a result, these nanoshells do not exhibit strong optical properties in the near-infrared region. This study highlights the importance of solvent effects on PEGylated nonprecious metal nanoparticles against oxidation corrosion and its applications in preserving physicochemical properties of metallic nanostructures.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2022

Experimental and theoretical study of hole scattering in RF sputtered p-type Cu 2 O thin films

One of the key materials of interest for p-type oxide semiconductor thin film electronics is cuprous oxide (Cu 2 O), due to its relatively high hole mobility. Here, in this work, we use experiments, analytical models, and density functional theory calculations to study the scattering mechanisms that determine Hall mobility in two Cu 2 O samples. First, we examine a polycrystalline Cu 2 O thin film deposited by RF magnetron sputtering, and second, a single-crystalline Cu2O bulk substrate. Temperature-dependent Hall measurements indicate that neutral impurity and grain boundary scattering are dominant for the polycrystalline Cu 2 O thin film, while phonon scattering is dominant for single-crystalline Cu 2 O. Our first-principles calculations show that the room-temperature intrinsic hole mobility of Cu 2 O is 106 cm 2 V –1 s –1 , indicating the great promise of the material for p-type electronic devices. This intrinsic mobility is limited by phonon scattering, with the most dominant scattering modes having phonon energies of 88.4 and 17.1 meV. These results indicate that the key pathways to increase the hole mobility in Cu 2 O thin films are by reducing the impurity concentration and by increasing grain size. Our work thus sets the stage for the future development of high performance Cu 2 O-based p-type thin film transistors.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Developing single-site Pt catalysts for the preferential oxidation of CO: A surface science and first principles-guided approach

Here, we report a comprehensive study combining surface science, Density Functional Theory (DFT) calculations, and catalyst synthesis, characterization, and testing to investigate the preferential oxidation of CO in the presence of H 2 over single-site Pt 1 /Cu x O catalysts. Surface science studies show that while Pt 1 /Cu x O model surfaces enable low-temperature CO oxidation via a Mars-van Krevelen mechanism, there was no evidence for H 2 activation or oxidation. DFT-based calculations explain these results and demonstrate that the H 2 oxidation barrier is high as compared to H 2 desorption from Pt 1 /Cu x O. Inspired by these model catalyst studies, nanoporous Pt 1 /Cu x O catalysts were synthesized and demonstrated to be active and highly selective for the preferential oxidation of CO. This work highlights the potential of combined surface science, theory, and catalyst studies for identifying new catalytic materials, which in this case led to the development of a promising single-site Pt 1 /Cu x O catalyst for the preferential oxidation of CO.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Elucidating facet dependent electronic and electrochemical properties of Cu 2 O nanocrystals using AFM/SCEM and DFT

Cuprous oxide (Cu 2 O) has extensively been studied owing to its excellent optical, magnetic, and catalytic properties. Many of these properties are facet-dependent and have not been well elucidated. This work synthesized cubic, cuboctahedral, octahedral, and rhombic dodecahedral shaped Cu 2 O nanocrystals of ~300 nm in size to evaluate the facet-dependent electrochemical activities. Here, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were firstly used to reveal the average electrochemical activities at the ensemble level. Atomic force microscopy-scanning electrochemical microscopy (AFM-SECM) was further used to assess the electrochemical activities of different Cu 2 O nanocrystals at the facet level. Hexaammineruthenium (III) chloride ({Ru(NH 3 ) 6 }Cl 3 ) was employed as the probe molecules that reacted with four different Cu 2 O nanocrystals under —400mV and yielded ~300 pA current between the probing tip and the nanocrystal surface. The tip-current mapping results indicate that rhombic dodecahedral Cu 2 O exhibits higher electrocatalytic activity than other shaped Cu 2 O, due to the presence of dominant exposed facet of {110} as indicated by the relatively high tip current. Density-functional theory (DFT) calculations confirmed the facet dependence of local surface energy and electronic structure of Cu 2 O nanocrystals. Besides electrochemical activity, the surface work function and adsorptive properties were both observed to vary with the shape and dominant exposed facets of Cu 2 O. This study presented a unique experimental and computational chemistry approach to analyze surface electrochemical properties of Cu 2 O crystals at a crystalline facet level.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Snowflake relocated Cu 2 O electrocatalyst on an Ag backbone template for the production of liquid C 2+ chemicals from CO 2

In this study, we performed the CO 2 reduction reaction (CO 2 RR) using a structural composite catalyst of cuprous oxide (Cu 2 O) and silver (Ag) that was simultaneously electrodeposited. While the underneath Ag electrodeposits maintained their spiky backbone structures even after the CO 2 RR, the Cu 2 O deposits were reduced to Cu(111) and relocated on the backbone template. Here, the structural changes in Cu 2 O to Cu increase the active area of the Cu–Ag interface, resulting in a remarkable production rate of 125.01 μmol h -1 of liquid C 2+ chemicals via the stabilization of the C–C coupling of the key intermediate species of acetaldehyde. This study provides new insights into designing a bimetallic catalyst for producing sustainable C 2+ products from CO 2 without any selectivity towards the production of methane.

36 MATERIALS SCIENCE↗