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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Robust Oxygen‐Vacancy‐Engineered Co(OH) 2 /Cu Heterostructures Boost Nitrate Electroreduction to Ammonia beyond 2 A cm −2

Electrocatalytic nitrate reduction reaction (NO 3 RR) presents a sustainable paradigm for green NH 3 synthesis and NO 3 − wastewater valorization. However, overcoming sluggish NO 3 RR kinetics under industrial-current operation persists as a critical challenge. Herein, robust oxygen vacancy-enriched heterostructures (O v -Co(OH) 2 /Cu) are engineered through in situ electrochemical reconstruction. By coupling Cu-mediated NO 3 − -to-NO 2 − conversion with O v -Co(OH) 2 -accelerated NO 2 − -to-NH 3 transformation, this heterostructured system delivers an unprecedented NH 3 yield rate of 167.8 mg h −1 cm −2 and 97.7% Faradaic efficiency at >2 A cm −2 , while maintaining exceptional current tolerance over 25 h. Operando spectroscopic characterizations and theoretical calculations reveal that the introduction of O v in Co(OH) 2 synergistically accelerates water dissociation to ensure continuous hydrogen supply and optimizes *NOOH adsorption, reducing the energy barrier for the rate-limiting step (*NO 2 to *NOOH). To demonstrate practical viability, a membrane-electrode-assembly electrolyzer integrating NO 3 RR with glycerol oxidation reaction achieves highly effective co-production of NH 3 and formate alongside wastewater treatment. In conclusion, this work offers new insights into the rational design of electrocatalysts through in situ reconstruction-induced vacancy engineering for scalable and practical NO 3 RR applications.

ammonia synthesis↗
DOE OSTI2024

Sustainedly High-Rate Electroreduction of CO 2 to Multi-Carbon Products on Nickel Oxygenate/Copper Interfacial Catalysts

Copper (Cu) is the most attractive electrocatalyst for CO 2 reduction to multi-carbon (C 2+ ) products with high economic value in considerable amounts. However, the rational design of a structurally stable Cu-based catalyst that can achieve high activity and stability towards C 2+ products remain a grand challenge. Here, in this study, a highly stable nickel oxygenate/Cu electrocatalyst is developed with abundant NiOOH/Cu interfaces by in situ electrochemical reconstruction. The nickel oxygenate/Cu electrocatalyst achieves a superior Faradaic efficiency of 86.3 ± 3.0% and a record partial current density of 2085 A g -1 for C 2+ products with long-term stability. In situ experimental and theoretical studies demonstrates that the exceptional performance in generating C 2+ products is attributed to the presence of the NiOOH/Cu interfaces which increase *CO coverage, lower energy barrier for *CO coupling and stabilize *OCCO simultaneously. This work provides new insights into the rational design of electrocatalysts to achieve stable and efficient electrocatalytic CO 2 reduction capabilities.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Facet‐Selective Deposition of Ultrathin Al 2 O 3 on Copper Nanocrystals for Highly Stable CO 2 Electroreduction to Ethylene

Abstract Catalysts based on Cu nanocrystals (NCs) for electrochemical CO 2 ‐to‐C 2+ conversion with high activity have been a subject of considerable interest, but poor stability and low selectivity for a single C 2+ product remain obstacles for realizing sustainable carbon‐neutral cycles. Here, we used the facet‐selective atomic layer deposition (FS‐ALD) technique to selectively cover the (111) surface of Cu NCs with ultrathin Al 2 O 3 to increase the exposed facet ratio of (100)/(111), resulting in a faradaic efficiency ratio of C 2 H 4 /CH 4 for overcoated Cu NCs 22 times higher than that for pure Cu NCs. Peak performance of the overcoated catalyst (Cu NCs/Al 2 O 3 ‐10C) reaches a C 2 H 4 faradaic efficiency of 60.4 % at a current density of 300 mA cm −2 in 5 M KOH electrolyte, when using a gas diffusion electrode flow cell. Moreover, the Al 2 O 3 overcoating effectively suppresses the dynamic mobility and the aggregation of Cu NCs, which explains the negligible activity loss and selectivity degradations of Cu NCs/Al 2 O 3 ‐10C shown in stability tests.

Li, Hui↗
DOE OSTI2021

Facet-Selective Deposition of Ultrathin Al 2 O 3 on Copper Nanocrystals for Highly Stable CO 2 Electroreduction to Ethylene.

Catalysts based on Cu nanocrystals (NCs) for electrochemical CO 2 -to- 2+ conversion with high activity have been a subject of considerable interest, but poor stability and low selectivity for a single C 2+ product remain obstacles for realizing sustainable carbon-neutral cycles. In this study, we used the facet-selective atomic layer deposition (FS-ALD) technique to selectively cover the (111) surface of Cu NCs with ultrathin Al 2 O 3 to increase the exposed facet ratio of (100)/(111), resulting in a faradaic efficiency ratio of C 2 H 4 /CH 4 for overcoated Cu NCs 22 times higher than that for pure Cu NCs. Peak performance of the overcoated catalyst (Cu NCs/Al 2 O 3 -10C) reaches a C 2 H 4 faradaic efficiency of 60.4 % at a current density of 300 mA cm -2 in 5 M KOH electrolyte, when using a gas diffusion electrode flow cell. Moreover, the Al 2 O 3 overcoating effectively suppresses the dynamic mobility and the aggregation of Cu NCs, which explains the negligible activity loss and selectivity degradations of Cu NCs/Al 2 O 3 -10C shown in stability tests.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Hollow-structured Ni-N-C catalysts for highly selective CO 2 electroreduction

Atomically dispersed single-atom catalysts have emerged as promising non-precious catalyst alternatives to expensive Ag and Au catalysts for electrochemical CO 2 reduction reaction (CO 2 RR). In particular, nickel-nitrogen-carbon (Ni-N-C) catalysts have demonstrated a high faradaic efficiency (FE) toward CO formation at low overpotentials. Nonetheless, the exact nature of Ni active sites under CO 2 RR remains elusive and conventional Ni-N-C catalysts are limited by microporosity and low density of Ni single atoms, hindering performance in CO 2 electrolyzers. Here, we report the synthesis of hollow-structured Ni-N-C ( hs -Ni-N-C) catalysts via a post-synthesis modification (PSM) strategy using partial ligand exchange of 2-methylimidazole with 3-amino-1,2,4-triazole. This approach enables the formation of a hollow structure, resulting in more than a twofold increase in Ni atom density compared to regular Ni-N-C (r-Ni-N-C). In a zero-gap CO 2 electrolyzer, the optimized hs -Ni-N-C allows for achieving an FE CO of 97% at a current density of > 100 mA cm⁻ 2 , while maintaining high CO selectivity with stable performance over 100 h at 2.5 V. hs-Ni-N-C shows a more than sevenfold increase in the CO partial current density relative to r-Ni-N-C resulting from the combined effects of a higher density of Ni single-atom sites, improved kinetics, and lower transport resistance under the operating conditions, as indicated by electrochemical impedance spectra and distribution of relaxation times analysis. Operando high energy-resolution X-ray absorption spectroscopy (XAS) reveals that atop-bonded CO on Ni single sites induces dynamic transformations of the Ni–N coordination environment, leading to a symmetric coordination structure of hs -Ni-N-C. Under CO 2 RR, the catalysts undergo a more pronounced structural change and form a minor fraction of Ni nanoparticles. Density functional theory calculations are consistent with the XAS results and provide molecular insights showing that the interplay between protonation and CO adsorption leads to adsorbate-induced restructuring of the Ni single atom. This work demonstrates the synergistic role of hollow structure and high-density Ni atoms in governing CO 2 RR selectivity and provides mechanistic insights into the structural dynamics of single-atom catalysts under operating conditions.

36 MATERIALS SCIENCE↗
DOE OSTI2022

The effect of catholyte and catalyst layer binders on CO 2 electroreduction selectivity

Electrochemical reduction of carbon dioxide (CO 2 ) is an attractive technology for converting CO 2 to value-added chemicals by using renewably generated electricity. This work combines both experimental and theoretical analyses to investigate the role of different catalysts (Ag/Vu and SnO 2 /Vu), binder materials, and catholyte compositions on the selectivity of a CO 2 electrolysis cell to the two-electron CO 2 reduction products CO and formate. As a complementary effort, a 2D multi-physics transport model was developed to elucidate the fundamental processes and species concentrations in the cathode components. It was shown that the selectivity of CO 2 reduction to CO can change significantly when different catholyte compositions and binder materials are used, whereas the selectivity of CO 2 to formate is relatively stable across the conditions studied. These insights can be used to inform decisions regarding the electrode development and system design in CO 2 electrolyzers and ultimately contribute to scaling energy-efficient electrochemical CO 2 -reduction systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Large-scale synthesis of metal/nitrogen Co-doped carbon catalysts for CO 2 electroreduction

In this work, we report a facile approach for synthesizing M–N–C catalysts (M = Co, Fe, Ni) at a commercial scale without employing organic solvents. Our characterization efforts indicate that single atomic catalysts with high surface areas were successfully obtained. Electrochemical measurements demonstrate that, among the three synthesized catalysts, Ni–N–C exhibits the highest performance in the electrochemical CO2 reduction reaction (CO 2 RR) to carbon monoxide (CO), affording 80% Faradaic efficiency (FE) of CO production at –0.49 V RHE with a turnover frequency (TOF) of 57,379 h –1 . Large-scale synthesis coupled with high performance allows moving forward with the practical implementation of M–N–C catalysts for industrially relevant CO 2 RR.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

A channel flow cell with double disk electrodes for oxygen electroreduction study at elevated temperatures and pressures: Theory

We report a new double-disk-electrode channel flow cell has been designed, constructed and tested. A theoretical treatment and implicit finite difference numerical simulations are presented, which permit the computation of the hydrodynamic behavior of this cell under steady state conditions, i.e., the diffusion limited current at the working electrode and the collection efficiency of the detector. The simulated results are consistent with those measured experimentally, indicating that our simulations appropriately describe the hydrodynamic behavior of this cell. The oxygen reduction reaction (ORR) on a carbon-supported nanoparticle Pt catalyst at both room temperature and 110 °C were preliminarily studied with this cell.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Trace level of atomic copper in N-doped graphene quantum dots switching the selectivity from C 1 to C 2 products in CO electroreduction

To unravel the relationship between trace Cu on the metal-free catalysts toward CO/CO 2 reduction reaction (CO/CO 2 RR), we investigated the effect of trace Cu loading in N-doped graphene quantum dots (NGQDs) on CO/CO 2 RR. A general trend is that increasing the Cu loading in NGQDs switches the selectivity from C 1 (CH 4 ) to C 2 products in CORR. When 2.5 μg/cm 2 Cu with the atomic size is loaded on NGQDs, the selectivity shifts from 62% Faradaic efficiency (FE) of CH 4 to 52% FE of C 2 products in CORR. Further increasing the atomic Cu loading to 3.8 μg/cm 2 promotes the FE of C 2 products to 78%. CO 2 RR requires one order of magnitude higher Cu loading than CORR to switch the selectivity from C 1 to C 2 products due to the low partial pressure of CO. Finally, this study clarifies the distinct impact of trace (ppm level) Cu on the activity/selectivity between CORR and CO 2 RR.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Engineering bimetallic interfaces and revealing the mechanism for carbon dioxide electroreduction to C 3+ liquid chemicals

Reduction reaction of CO 2 (CO 2 RR) to liquid C 3+ chemicals is a net-zero-carbon process and can increase local resiliency to power outages and fuel consumption. The mechanism and the catalyst design rules of CO 2 RR-to-C 3+ are unknown. Engineering bimetallic interface (e.g., Pd/Au) to tune the intermediate adsorption is promising for promoting C 3+ formation. Our density functional theory (DFT) calculations find that *CH 2 could be the key intermediate and C 1 -CH 2 coupling could be the rate-limiting step to generate C 3+ . High CO surface coverages can promote the bimetallic interfacial sites, lower the energetics of the C 1 -CH 2 coupling step, and enhance the C 3+ formation. We further construct a volcano plot of C 1 -CH 2 kinetics as a function of the binding strength of key intermediate *CH 2 via engineering the d-band center of the interfacial site. Our findings could guide the rational design of bimetallic interfaces and their near-surface microenvironment for enhancing CO 2 RR-to-C 3+ .

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2023

A Dicationic fac -Re(bpy)(CO) 3 Cl for CO 2 Electroreduction at a Reduced Overpotential

Here, a dicationic Re bipyridine-type complex, fac-Re(6,6'-(2-((trimethylammonio)-methyl)phenyl)-2,2'-bipyridine)(CO) 3 Cl hexafluorophosphate (1 2+ ), has been synthesized and its electrochemical behavior under Ar and CO 2 has been investigated. The presence of pendent tetra-alkylammonium cations induces an anodic shift in the electrocatalytic potential for CO 2 reduction relative to structurally similar model complexes. The electrochemical mechanisms in anhydrous CH 3 CN and in the presence of weak acids (water or trifluoroethanol) have been analyzed using cyclic voltammetry assisted by infrared spectroelectrochemistry and theoretical calculations. The dication enables catalysis at a diminished potential through coulombic stabilization of the doubly reduced pentacoordinate species, its CO 2 adduct, the hydroxide anion, and the conjugate base formed during acid-assisted C-OH bond cleavage of the metallocarboxylic acid to the metallocarbonyl and H 2 O. The major reduction product is CO, but in the presence of trifluoroethanol, formate is also produced with 14% Faradaic efficiency.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Electroreduction-Driven Formation and Connectivity of Polyoxometalate Coordination Networks

We present the synthesis of metal oxide coordination networks based on Preyssler-type polyoxoanions ([NaP 5 W 30 O 110 ] 14– and [NaP 5 MoW 29 O 110 ] 14– ) bridged with metal–aquo complexes ([M(H 2 O) n ] m+ , M m+ = Co 2+ , Ni 2+ , Zn 2+ , Y 3+ ), induced by electrochemical reduction. Networks bridged with first-row transition metals are isostructural with a previously reported Co-bridged structure, while the Y 3+ -bridged structure is new. All networks feature an uncommon binding motif of the metal cation to the oxygen atoms at cap positions, which we hypothesize is due to increased electron density at the cap upon reduction. Oxidation of a Zn 2+ -bridged network resulted in a new structure in which Zn 2+ –O cap bonds are lost, indicating the importance of reduction in the connectivity of these polyoxometalate-based coordination networks.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗