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Results for “urea oxidation”

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

Single-Phase Spinel NiCo 2 O 4 as Highly Active and Stable Electrocatalysts for Urea Oxidation Reaction in Urea Electrolysis

Exploring and designing a stable and active catalyst for the urea electro-oxidation reaction (UOR, CO(NH 2 ) 2 + 6OH – → CO 2 + N 2 + 5H 2 O + 6e – ) is crucial for the long-term sustainability of ecological systems and clean energy production. We found that spinel NiCo 2 O 4 is a stable and active electrocatalyst for UOR at a relatively low anodic potential without triggering the competing oxygen evolution reaction (OER). A urea electrolysis cell (CO(NH 2 )2 + H 2 O → CO 2 + N 2 + 2H 2 ) utilizing a spinel NiCo 2 O 4 anode and a commercial Pt cathode was further characterized through galvanostatic polarization tests, demonstrating excellent structural stability at various current densities. Post-mortem analysis of long-term urea electrolysis measurements suggested that NiCo 2 O 4 electrocatalysts maintained a stable spinel structure. However, redistribution of Ni 3+ to Ni 2+ valence on the catalyst surface was observed, in contrast to the intact Co valence, indicating that (i) Ni sites are active toward urea adsorption and sequential electro-oxidation; (ii) while urea oxidation proceeds primarily through the direct electro-oxidation mechanism, chemical reactions between the Ni 3+ site and urea occur during long-term electrochemical UOR operation. Density functional theory (DFT) simulations were used to calculate the adsorption energies of urea molecules on NiO, Co 3 O 4 , and NiCo 2 O 4 , revealing the importance of regulating the configuration of adsorbed urea molecules on the NiCo 2 O 4 surface.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Density Functional Theory Investigation of the NiO@Graphene Composite as a Urea Oxidation Catalyst in the Alkaline Electrolyte

Developing efficient and low-cost urea oxidation reaction (UOR) catalysts is a promising but still challenging task for environment and energy conversion technologies such as wastewater remediation and urea electrolysis. In this work, NiO nanoparticles that incorporated graphene as the NiO@Graphene composite were constructed to study the UOR process in terms of density functional theory. The single-atom model, which differed from the previous heterojunction model, was employed for the adsorption/desorption of urea and CO 2 in the alkaline media. As demonstrated from the calculated results, NiO@Graphene prefers to adsorb the hydroxyl group than urea in the initial stage due to the stronger adsorption energy of the hydroxyl group. After NiOOH@Graphene was formed in the alkaline electrolyte, it presents excellent desorption energy of CO 2 in the rate-determining step. Electronic density difference and the d band center diagram further confirmed that the Ni(III) species is the most favorable site for urea oxidation while facilitating charge transfer between urea and NiO@Graphene. Moreover, graphene provides a large surface for the incorporation of NiO nanoparticles, enhancing the electron transfer between NiOOH and graphene and promoting the mass transport in the alkaline electrolyte. Notably, this work provides theoretical guidance for the electrochemical urea oxidation work.

25 ENERGY STORAGE↗
DOE OSTI2023

Enhanced Urea Oxidation Electrocatalytic Activity by Synergistic Cobalt and Nickel Mixed Oxides

In this study, exploring reactive and selective Ni-based electrocatalysts for the urea oxidation reaction (UOR) is crucial for developing urea-related energy conversion technologies. Herein, synergistic interactions in Ni/Co mixed oxides/hydroxides enhanced the UOR with low onset potential, fast reaction kinetics, and good selectivity against oxygen evolution reaction (OER). Our electrochemical measurements and theoretical calculations signified the collaborative interaction of Ni/Co mixed oxide/hydroxide heterostructures to enhance UOR activity. Our results showed that Ni 3+ species, formed at high anodic potential, produced a high anodic current primarily from unwanted OER. Instead, the Ni/Co heterostructures with dominant Ni 2+ and Co 3+ species remained stable at low anodic potential and exhibited anodic current exclusively attributed to UOR. This work highlights the importance of tuning valence charges for designing high-performance and selective UOR electrocatalysts to benefit the environmental remediation of urea runoff and enable urea electrolysis for hydrogen production by replacing conventional OER with UOR at the anode.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Highly Efficient Urea Oxidation via Nesting Nano-Nickel Oxide in Eggshell Membrane-Derived Carbon

Here, we reported a strategy of using an eggshell membrane to produce hierarchically porous carbon as a low-cost substrate for synthesizing a nano-nickel oxide catalyst (C@NiO), which can effectively turn biowaste—urea—into energy through an electrochemical approach. Here, the interwoven carbon networks within NiO led to highly efficient urea oxidation due to the strong synergistic effect. The as-prepared electrode only needed 1.36 V versus reversible hydrogen electrode to realize a high efficiency of 10 mA cm –2 in 1.0 M KOH with 0.33 M urea and delivered an even higher current density of 25 mA cm –2 at 1.46 V, which is smaller than that of the porous carbon and commercial Pt/C catalyst. Benefiting from theoretical calculations, Ni(III) active species and the porous carbon further enabled the electrocatalyst to effectively inhibit the “CO 2 poisoning” of electrocatalysts, as well as ensuring its superior performance for urea oxidation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1989

Selective removal of organics for water reclamation

Electrolysis has been investigated as a means of purifying waste water. The feasibility of the direct electrochemical oxidation of urea has been demonstrated. Urea levels were reduced from 1200 ppm to 1 ppm forming the basis for a new approach to urine purification where the only consumable is electrical energy. Preliminary estimates of the energy requirements are 270 W/hr per liter of urine. Urea oxidation rates of around 350 mg urea/hr/m2 were observed. It is anticipated that a 1 m2 geometric area of electrode could treat urine for a crew of several persons. The low levels of organic contaminants resulting from this treatment indicate that the approach may have an impact as a post treatment process. Experiments are planned to investigate this later possibility.

Murphy, Oliver J.↗
DOE OSTI2023

Atomically dispersed Pt single sites and nanoengineered structural defects enable a high electrocatalytic activity and durability for hydrogen evolution reaction and overall urea electrolysis

The scarcity and high cost of PGM electrocatalysts are the key bottleneck in the mass-scale commercialization of many electrolysis technologies. Bifunctional single-atom electrocatalysts (SACs) are promising alternatives for PGM electrocatalysts in next-generation electrolysis technologies because of their superior intrinsic activity and perfect atom utilization. Regulating the coordination environment of platinum atomic sites identifies their electrocatalytic performance. Therefore, exploring more appropriate supports could facilitate the construction of active and durable electrocatalysts with ultralow noble metal content. Herein, we report on a reliable approach for producing a novel type of SACs composed of atomically dispersed Pt active sites stabilized on defective NiCo layered double hydroxide (Pt/D-NiCo LDH) nanosheets as an ultralow-Pt hybrid electrocatalyst for hydrogen evolution reaction (HER), urea oxidation reaction (UOR), and full urea-water electrolysis. The optimized Pt 1 /D NiCo LDH-24 SAC displays a remarkable HER and UOR performance where it yields a current density of 10 mA cm -2 at 37 mV and 1.25 V vs. RHE for HER and UOR, respectively. Finally, symmetrical urea electrolyzer constructed of Pt 1 /D-NiCo LDH-24 electrodes attains 10 mA cm -2 at a cell voltage of 1.32 V vs. RHE, demonstrating superior activity and durability over 60 h operation when compared to commercial Pt/C( + )||RuO 2 ( - ) system.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Impact of a Novel Nickel-Based Catalyst and Phenyl-Acrylate-Based Anion-Exchange Membrane in a Direct Urea Fuel Cell

Developing target-specific catalysts and anion-exchange membranes (AEMs) is crucial for direct urea fuel cell (DUFC) performance. To advance the DUFC system, we developed an anode catalyst with a nickel–iron oxyhydroxide/carbon (NiFeOOH/C) nanofibrous structure for the urea oxidation reaction (UOR), where we optimized the Ni/Fe molar ratio as 6:4. The enhanced electrocatalytic activity of the anode (Ni 6 Fe 4 OOH/C) is attributed to the hydroxide group, which responds with urea molecules to enhance the UOR in a pH-neutral system. Here, we employed a recently developed cross-linked phenyl-acrylate-based AEM (PA/M). A DUFC prepared with the anode and PA/M generates a maximum power density of 11.1 mW/cm 2 and 0.92 V open-circuit voltage under 3 M urea as fuel at 25 °C. We further analyzed the applicability of PA/M in a DUFC system by measuring the urea partition coefficients and permeabilities over a range of concentrations.

10 SYNTHETIC FUELS↗
DOE OSTI2024

Double Hydroxide Nanocatalysts for Urea Electrooxidation Engineered toward Environmentally Benign Products

Abstract Recent advancements in the electrochemical urea oxidation reaction (UOR) present promising avenues for wastewater remediation and energy recovery. Despite progress toward optimized efficiency, hurdles persist in steering oxidation products away from environmentally unfriendly products, mostly due to a lack of understanding of structure‐selectivity relationships. In this study, the UOR performance of Ni and Cu double hydroxides, which show marked differences in their reactivity and selectivity is evaluated. CuCo hydroxides predominantly produce N 2 , reaching a current density of 20 mA cm geo −2 at 1.04 V – 250 mV less than NiCo hydroxides that generate nitrogen oxides. A collection of in‐situ spectroscopies and scattering experiments reveal a unique in situ generated Cu (2‐x)+ ‐OO −• active sites in CuCo, which initiates nucleophilic substitution of NH 2 from the amide, leading to N‐N coupling between * NH on Co and Cu. In contrast, the formation of nitrogen oxides on NiCo is primarily attributed to the presence of high‐valence Ni 3+ and Ni 4+ , which facilitates N‐H activation. This process, in conjunction with the excessive accumulation of OH − ions on Jahn‐Teller (JT) distorted Co sites, leads to the generation of NO 2 − as the primary product. This work underscores the importance of catalyst composition and structural engineering in tailoring innocuous UOR products.

36 MATERIALS SCIENCE↗
NASA NTRS2018

Effect of Additives: Gamma-Ray Sensors Based on Ionizing Organic Nanocomposites

We have developed ionizing organic-based composites which have demonstrated great promise for radiation sensing. Nickel oxide has been proven as an active material for detecting high energy radiation. The oxidation state of unusual oxides such as nickel oxide in nanocomposites of ionizing organics changes much faster than thin film or bulk, and hence increases the sensitivity for radiation sensing. The resistivity of the oxide composite increases following sequential irradiation processes because of the decrease in holes' concentration. In this paper, we will present the effect of additional oxidizing agent on the morphology, processing and sensing of gamma-rays by oxides - urea based nanocomposites. It was observed that addition of MnO2 decreases the sensitivity. However, it recovers to original properties after irradiation much faster than undoped composites.

Vishall Dayal↗
NASA NTRS1982

Supercritical water oxidation for wastewater treatment Preliminary study of urea destruction

Supercritical water oxidation is being investigated as a method of treating spacecraft wastewater for recycle. In this process, oxidation is conducted in an aqueous phase maintained above the critical temperature (374 C) and pressure (215 bar) of water. Organic materials are oxidized with efficiencies greater than 99.99 percent in residence times of less than 1 minute. This paper presents preliminary results for urea destruction. Above 650 C, urea can be completely broken down to nitrogen gas, carbon dioxide and water by supercritical water oxidation, without the use of a specific catalyst.

Timberlake, S. H.↗
DOE OSTI2026

Urea-to-Ammonia Conversion at Proteus mirabilis Modified Pt–Ni/BDD Electrodes

Efficient wastewater recycling technologies are essential for long-duration space missions and sustainable water management on Earth. Here, a bioelectrochemical system integrating Proteus mirabilis with a platinum–nickel-modified boron-doped diamond electrode (Pt–Ni/BDDE) for urea-to-ammonia conversion in synthetic urine is presented. Immobilized P. mirabilis catalyzes enzymatic ureolysis, converting urea into ammonia, which is subsequently oxidized electrochemically, and no direct electrochemical urea oxidation is observed. Cyclic voltammetry (CV) of P. mirabilis on Pt–Ni/BDDE in 0.1 M urea and synthetic urine revealed a broad anodic oxidation peak at approximately 0.55–0.75 V vs Ag/AgCl (sat. KCl), corresponding to ammonia oxidation. Control experiments using bare BDDE and Pt–Ni/BDDE in synthetic urine showed no oxidation peak, establishing that the bioelectrocatalytic response originates exclusively from the bioelectrode interface. Chronoamperometry studies revealed that immobilization potential and time critically influenced bacterial adhesion and electrochemical response, with optimal conditions yielding a maximum current density of 0.0055 mA·cm –2 . These quantitative results establish that microbial ureolysis can be efficiently coupled with advanced electrode materials for urea-to-ammonia conversion, offering a promising self-sustaining strategy for urine processing and water recovery in closed-loop life support systems.

Ammonia↗
NASA NTRS1977

Electrolytic pretreatment of urine

Electrolysis has been under evaluation for several years as a process to pretreat urine for ultimate recovery of potable water in manned spacecraft applications. The conclusions that were drawn from this investigation are the following: (1) A platinum alloy containing 10 percent rhodium has been shown to be an effective, corrosion-resistant anode material for the electrolytic pretreatment of urine. Black platinum has been found to be suitable as a cathode material. (2) The mechanism of the reactions occurring during the electrolysis of urine is two-stage: (a) a total Kjeldahl nitrogen and total organic carbon (TOC) removal in the first stage is the result of electrochemical oxidation of urea to CO2, H2O, and ammonia followed by chloride interaction to produce N2 from ammonia, (b) after the urea has been essentially removed and the chloride ions have no more ammonia to interact with, the chloride ions start to oxidize to higher valence states, thus producing perchlorates. (3) Formation of perchlorates can be suppressed by high/low current operation, elevated temperature, and pH adjustment. (4) UV-radiation showed promise in assisting electrolytic TOC removal in beaker tests, but was not substantiated in limited single cell testing. This may have been due to non-optimum configurations of the single cell test rig and the light source.

Source record↗
DOE OSTI2021

Use of microbial carbonation process to enable self‑carbonation of reactive MgO cement mixes

The low hydration and carbonation of reactive MgO cement (RMC) under ambient conditions causes prolonged setting and low compressive strengths (~4 MPa). This study proposed a unique technique which led to the enhancement of the hydration and carbonation processes via the synergistic combination of microbial carbonation process (MCP) with a hydration agent (HA) that enabled the self‑carbonation of RMC-based mixes without using of any special curing environments. Through hydrolysing urea (CO(NH{sub 2}){sub 2}) using ureolytic bacteria, CO{sub 3}{sup 2−} ions were produced to facilitate the carbonation of dissolved Mg{sup 2+} ions to form hydrated magnesium hydroxy carbonates (HMHCs). The self‑carbonation of RMC enabled by the MCP resulted in formation of brucite with a poor crystallinity and its rapid conversion into HMHCs, which improved the setting time and compressive strength of RMC-based samples. The simultaneous use of MCP with 2 M urea and HA revealed HMHCs with improved morphologies, resulting in the highest compressive strength (~15 MPa).

36 MATERIALS SCIENCE↗
DOE OSTI2023

Minimum conditions for accurate modeling of urea production via co-electrolysis

Co-electrolysis of carbon oxides and nitrogen oxides promise to simultaneously help restore the balance of the C and N cycles while producing valuable chemicals such as urea. However, co-electrolysis processes are still largely inefficient and numerous knowledge voids persist. Here, we provide a solid thermodynamic basis for modelling urea production via co-electrolysis. First, we determine the energetics of aqueous urea produced under electrochemical conditions based on experimental data, which enables an accurate assessment of equilibrium potentials and overpotentials. Next, we use density functional theory (DFT) calculations to model various co-electrolysis reactions producing urea. The calculated reaction free energies deviate significantly from experimental values for well-known GGA, meta-GGA and hybrid functionals. These deviations stem from errors in the DFT-calculated energies of molecular reactants and products. In particular, the error for urea is approximately -0.25 ± 0.10 eV. Finally, we show that all these errors introduce large inconsistencies in the calculated free-energy diagrams of urea production via co-electrolysis, such that gas-phase corrections are strongly advised.

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

Proposed synthesis of a linear poly-ethylenimine with hydroxyl pendants substituents at the adjacent carbon

The synthesis of a linear poly-ethylenimine with pendant hydroxyl groups bonded to backbone carbons adjacent to the backbone amine groups is investigated and compared to the conventional method of functionalizing branched poly-ethylenimine using epoxides for use in direct air capture of carbon dioxide. The addition of hydroxyl groups imparts stability against both oxidative degradation and the formation of urea by reducing the number of primary amines, while the novel method of bonding to the adjacent backbone carbon rather than directly to the amine is hypothesized to retain the higher capacity for carbon dioxide of secondary amines when compared to tertiary amines. We also expect that the hydroxyl substituents will impart stronger hydrogen bonding capabilities, resulting in stronger interactions between adjacent polymer chains and a subsequent decrease in mobility.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Discovery of an ultraspecific triuret hydrolase (TrtA) establishes the triuret biodegradation pathway

Triuret (carbonyldiurea) is an impurity found in industrial urea fertilizer (<0.1% w/w) that is applied, worldwide, around 300 million pounds each year on agricultural lands. In addition to anthropogenic sources, endogenous triuret has been identified in amoeba and human urine, the latter being diagnostic for hypokalemia. The present study is the first to describe the metabolic breakdown of triuret, which funnels into biuret metabolism. We identified the gene responsible for triuret decomposition ( trtA ) in bacterial genomes, clustered with biuH , which encodes biuret hydrolase and has close protein sequence homology. TrtA is a member of the isochorismatase-like hydrolase (IHL) protein family, similarly to BiuH, and has a catalytic efficiency (k cat/ K M ) of 6 x 10 5 M –1 s –1 , a K M for triuret of 20 μM, and exquisite substrate specificity. Indeed, TrtA has four orders of magnitude less activity with biuret. Crystal structures of TrtA in apo and holo form were solved and compared with the BiuH structure. The high substrate selectivity was found to be conveyed by second shell residues around each active site. Mutagenesis of residues conserved in TrtA to the alternate consensus found in BiuHs revealed residues critical to triuret hydrolase activity but no single mutant evolved more biuret activity, and likely a combination of mutations is required to interconvert between TrtA, BiuH functions. TrtA-mediated triuret metabolism is relatively rare in recorded genomes (1–2%), but is largely found in plant-associated, nodulating, and endophytic bacteria. This study suggests functions for triuret hydrolase in certain eukaryotic intermediary processes and prokaryotic intermediary or biodegradative metabolism.

36 MATERIALS SCIENCE↗