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Nguyen-Phan TD, Hu L, Howard BH, Xu W, Stavitski E, Leshchev D, Rothenberger A, Neyerlin KC, Kauffman DR. High current density electroreduction of CO 2 into formate with tin oxide nanospheres. Sci Rep 2022; 12:8420. [PMID: 35589777 PMCID: PMC9120473 DOI: 10.1038/s41598-022-11890-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Accepted: 04/29/2022] [Indexed: 11/20/2022] Open
Abstract
In this study, we demonstrate three-dimensional (3D) hollow nanosphere electrocatalysts for CO2 conversion into formate with excellent H-Cell performance and industrially-relevant current density in a 25 cm2 membrane electrode assembly electrolyzer device. Varying calcination temperature maximized formate production via optimizing the crystallinity and particle size of the constituent SnO2 nanoparticles. The best performing SnO2 nanosphere catalysts contained ~ 7.5 nm nanocrystals and produced 71–81% formate Faradaic efficiency (FE) between −0.9 V and −1.3 V vs. the reversible hydrogen electrode (RHE) at a maximum formate partial current density of 73 ± 2 mA cmgeo−2 at −1.3 V vs. RHE. The higher performance of nanosphere catalysts over SnO2 nanoparticles and commercially-available catalyst could be ascribed to their initial structure providing higher electrochemical surface area and preventing extensive nanocrystal growth during CO2 reduction. Our results are among the highest performance reported for SnO2 electrocatalysts in aqueous H-cells. We observed an average 68 ± 8% FE over 35 h of operation with multiple on/off cycles. In situ Raman and time-dependent X-ray diffraction measurements identified metallic Sn as electrocatalytic active sites during long-term operation. Further evaluation in a 25 cm2 electrolyzer cell demonstrated impressive performance with a sustained current density of 500 mA cmgeo−2 and an average 75 ± 6% formate FE over 24 h of operation. Our results provide additional design concepts for boosting the performance of formate-producing catalysts.
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Affiliation(s)
- Thuy-Duong Nguyen-Phan
- National Energy Technology Laboratory, 626 Cochrans Mill Road, P.O. Box 10940, Pittsburgh, PA, 15236-0940, USA. .,NETL Support Contractor, 626 Cochrans Mill Road, P.O. Box 10940, Pittsburgh, PA, 15236-0940, USA.
| | - Leiming Hu
- National Renewable Energy Laboratory, Golden, CO, 80401, USA
| | - Bret H Howard
- National Energy Technology Laboratory, 626 Cochrans Mill Road, P.O. Box 10940, Pittsburgh, PA, 15236-0940, USA
| | - Wenqian Xu
- X-Ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, IL, 60439, USA
| | - Eli Stavitski
- Photon Sciences Division, National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - Denis Leshchev
- Photon Sciences Division, National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - August Rothenberger
- National Energy Technology Laboratory, 626 Cochrans Mill Road, P.O. Box 10940, Pittsburgh, PA, 15236-0940, USA
| | | | - Douglas R Kauffman
- National Energy Technology Laboratory, 626 Cochrans Mill Road, P.O. Box 10940, Pittsburgh, PA, 15236-0940, USA.
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Fernandez PM, Bloem E, Binley A, Philippe RSBA, French HK. Monitoring redox sensitive conditions at the groundwater interface using electrical resistivity and self-potential. JOURNAL OF CONTAMINANT HYDROLOGY 2019; 226:103517. [PMID: 31280034 DOI: 10.1016/j.jconhyd.2019.103517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Revised: 05/23/2019] [Accepted: 06/20/2019] [Indexed: 06/09/2023]
Abstract
Assessing redox conditions in soil and groundwater is challenging because redox reactions are oxygen sensitive, hence, destructive sampling methods may provide contact with air and influence the redox state. Furthermore, commonly used redox potential sensors provide only point measurements and are prone to error. This paper assesses whether combining electrical resistivity (ER) and self-potential (SP) measurements can allow the mapping of zones affected by anaerobic degradation. We use ER imaging because anaerobic degradation can release iron and manganese ions, which decreases pore water resistivity, and produces gas, which increases resistivity. Also, electrochemical differences between anaerobic and aerobic zones may create an electron flow, forming a self-potential anomaly. In this laboratory study, with four sand tanks with constant water table heights, time-lapse ER and SP mapped changes in electrical/electron flow properties due to organic contaminant (propylene glycol) degradation. Sampled pore water mapped degradation and water chemistry. When iron and manganese oxides were available, degradation reduced resistivity, because of cation release in pore water. When iron and manganese oxides were unavailable, resistivity increased, plausibly from methane production, which reduced water saturation. To bypass the reactions producing methane and release of metallic cations, a metal pipe was installed in the sand tanks between anaerobic and aerobic zones. The degradation creates an electron surplus at the anaerobic degradation site. The metal pipe allowed electron flow from the anaerobic degradation site to the oxygen-rich near surface. The electrical current sent through the metal pipe formed an SP anomaly observable on the surface of the sand tank. Time-lapse ER demonstrates potential for mapping degradation zones under anaerobic conditions. When an electrical conductor bridges the anaerobic zone with the near surface, the electron flow causes an SP anomaly on the surface. However, electrochemical differences between anaerobic and aerobic zones alone produced no SP signal. Despite their limitations, ER and SP are promising tools for monitoring redox sensitive conditions in unsaturated sandy soils but should not be used in isolation.
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Affiliation(s)
- Perrine M Fernandez
- Norwegian University of Life Sciences (NMBU), Universitetstunet 3, 1430 Ås, Norway.
| | - Esther Bloem
- Norwegian Institute of Bioeconomy Research (NIBIO), Høgskoleveien 7, 1430 Ås, Norway.
| | - Andrew Binley
- Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, United Kingdom.
| | | | - Helen K French
- Norwegian University of Life Sciences (NMBU), Universitetstunet 3, 1430 Ås, Norway; Norwegian Institute of Bioeconomy Research (NIBIO), Høgskoleveien 7, 1430 Ås, Norway.
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Fernandez PM, Binley A, Bloem E, French HK. Laboratory spectral induced polarisation signatures associated with iron and manganese oxide dissolution because of anaerobic degradation. JOURNAL OF CONTAMINANT HYDROLOGY 2019; 221:1-10. [PMID: 30600103 DOI: 10.1016/j.jconhyd.2018.12.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Revised: 12/05/2018] [Accepted: 12/15/2018] [Indexed: 06/09/2023]
Abstract
Degradation of organic chemicals in natural soils depends on oxidation-reduction conditions. To protect our groundwater resources we need to understand the degradation processes under anaerobic conditions. Available iron and manganese oxides are used as electron acceptors for anaerobic degradation and are reduced to the dissolved form of metallic cations in pore water. To monitor this process is a challenge, because anaerobic conditions are difficult to sample directly without introducing oxygen. A few studies have shown an impact of iron reduction on spectral induced polarisation (SIP) signature, often associated with bacterial growth. Our objective is to study the impact of iron and manganese oxide dissolution, caused by degradation of an organic compound, with spectral induced polarisation signatures. Twenty-six vertical columns (30 cm high, inner diameter 4.6 cm) were filled with a sand rich in oxides (manganese and iron) with a static water table in the middle. In half of the columns, a 2 cm high contaminated layer was installed just above the water table. As the contaminant degrades, the initial oxygen is consumed and anaerobic conditions form Every three days over a period of one month, spectral induced polarisation (twenty frequencies between 5mHz and 10 kHz) data were collected on six columns: three contaminated replicates and three control replicates. Chemical analysis was done on twenty columns assigned for destructive water sampling, ten contaminated columns and ten control. The results show an increase of the real conductivity associated with the degradation processes, independent of frequency. Compared with the pore water electrical conductivity in the saturated zone, the real conductivity measurement revealed the formation of surface conductivity before iron was released in the pore water. In parallel, we also observed an evolution of the imaginary conductivity in both saturated and unsaturated zones at frequencies below 1 Hz. Overall, the anaerobic reduction of iron and manganese oxide during the organic degradation increased both the conductive and polarisation component of the complex conductivity.
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Affiliation(s)
- Perrine M Fernandez
- Norwegian University of Life Sciences (NMBU), Universitetstunet 3, 1430 Ås, Norway.
| | - Andrew Binley
- Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, United Kingdom.
| | - Esther Bloem
- Norwegian Institute of Bioeconomy Research (NIBIO), Høgskoleveien 7, 1430 Ås, Norway.
| | - Helen K French
- Norwegian University of Life Sciences (NMBU), Universitetstunet 3, 1430 Ås, Norway; Norwegian Institute of Bioeconomy Research (NIBIO), Høgskoleveien 7, 1430 Ås, Norway.
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Lissner H, Wehrer M, Reinicke M, Horváth N, Totsche KU. Constraints of propylene glycol degradation at low temperatures and saturated flow conditions. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2015; 22:3158-3174. [PMID: 25239107 DOI: 10.1007/s11356-014-3506-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2014] [Accepted: 08/21/2014] [Indexed: 06/03/2023]
Abstract
During snowmelt, the infiltration of large amounts of propylene glycol (PG), the major compound of many aircraft deicing fluids, affects redox processes and poses a contamination risk for the groundwater. To gain a better understanding about the degradation of PG and the associated biogeochemical processes under these conditions, we conducted saturated soil column experiments at 4 °C. During two successive PG pulses, we monitored the effect of the runway deicer formate (FO) and changing redox conditions on PG degradation. Furthermore, we applied first-order and simplified Monod kinetics to describe PG and FO transport. The transport of 50 mg l(-1) PG showed three stages of microbial degradation, which were defined as lag phase, aerobic phase, and anaerobic phase. During the second pulse, lag effects diminished due to the already accomplished microbial adaption, and the initial degradation rate of PG increased. Degradation of PG was most efficient during aerobic conditions (aerobic phase), while the subsequent drop of the redox potential down to -300 mV decreased the degradation rate (anaerobic phase). Formate addition decreased the overall degradation of PG by 50 and 15 % during the first and second pulse, illustrating the inhibitory effect of FO on PG degradation. The concurrent increase of Fe(III), organic carbon, and the turbidity in the column effluent after PG and FO application suggest the combined export of Fe adsorbed to fragments of detached biofilm. Neither the first-order nor the simplified Monod model was able to reconstruct the dynamic breakthrough of 50 mg l(-1) PG. The breakthrough of 1,000 mg l(-1), however, was described reasonably well with first-order kinetics. At low temperature and high water saturation, the application of first-order degradation kinetics seems therefore appropriate to describe the transport of high concentrations of PG.
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Affiliation(s)
- Heidi Lissner
- Institut für Geowissenschaften, Friedrich-Schiller-Universität Jena, Burgweg 11, 07749, Jena, Germany,
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French HK, Kästner M, van der Zee SEATM. New approaches for low-invasive contaminated site characterization, monitoring and modelling. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2014; 21:8893-6. [PMID: 24756671 DOI: 10.1007/s11356-014-2840-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Accepted: 03/25/2014] [Indexed: 05/26/2023]
Affiliation(s)
- Helen K French
- Environmental Sciences, Norwegian University of Life Sciences, P.O.Box. 5003, 1432, Ås, Norway,
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Biró B, Toscano G, Horváth N, Matics H, Domonkos M, Scotti R, Rao MA, Wejden B, French HK. Vertical and horizontal distributions of microbial abundances and enzymatic activities in propylene-glycol-affected soils. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2014; 21:9095-9108. [PMID: 24627198 DOI: 10.1007/s11356-014-2686-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2013] [Accepted: 02/19/2014] [Indexed: 06/03/2023]
Abstract
The natural microbial activity in the unsaturated soil is vital for protecting groundwater in areas where high loads of biodegradable contaminants are supplied to the surface, which usually is the case for airports using aircraft de-icing fluids (ADF) in the cold season. Horizontal and vertical distributions of microbial abundance were assessed along the western runway of Oslo Airport (Gardermoen, Norway) to monitor the effect of ADF dispersion with special reference to the component with the highest chemical oxygen demand (COD), propylene glycol (PG). Microbial abundance was evaluated by several biondicators: colony-forming units (CFU) of some physiological groups (aerobic and anaerobic heterotrophs and microscopic fungi), most probable numbers (MPN) of PG degraders, selected catabolic enzymatic activities (fluorescein diacetate (FDA) hydrolase, dehydrogenase, and β-glucosidase). High correlations were found between the enzymatic activities and microbial counts in vertical soil profiles. All microbial abundance indicators showed a steep drop in the first meter of soil depth. The vertical distribution of microbial abundance can be correlated by a decreasing exponential function of depth. The horizontal trend of microbial abundance (evaluated as total aerobic CFU, MPN of PG-degraders, and FDA hydrolase activity) assessed in the surface soil at an increasing distance from the runway is correlated negatively with the PG and COD loads, suggesting the relevance of other chemicals in the modulation of microbial growth. The possible role of potassium formate, component of runway de-icers, has been tested in the laboratory by using mixed cultures of Pseudomonas spp., obtained by enrichment with a selective PG medium from soil samples taken at the most contaminated area near the runway. The inhibitory effect of formate on the growth of PG degraders is proven by the reduction of biomass yield on PG in the presence of formate.
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Affiliation(s)
- Borbála Biró
- Institute for Soil Sciences and Agricultural Chemistry, Centre for Agricultural Research, Hungarian Academy of Sciences, Budapest, Hungary,
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Wehrer M, Lissner H, Bloem E, French H, Totsche KU. Electrical resistivity tomography as monitoring tool for unsaturated zone transport: an example of preferential transport of deicing chemicals. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2013; 21:8964-8980. [PMID: 24194415 DOI: 10.1007/s11356-013-2252-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2013] [Accepted: 10/15/2013] [Indexed: 06/02/2023]
Abstract
Non-invasive spatially resolved monitoring techniques may hold the key to observe heterogeneous flow and transport behavior of contaminants in soils. In this study, time-lapse electrical resistivity tomography (ERT) was employed during an infiltration experiment with deicing chemical in a small field lysimeter. Deicing chemicals like potassium formate, which frequently impact soils on airport sites, were infiltrated during snow melt. Chemical composition of seepage water and the electrical response was recorded over the spring period 2010. Time-lapse electrical resistivity tomographs are able to show the infiltration of the melt water loaded with ionic constituents of deicing chemicals and their degradation product hydrogen carbonate. The tomographs indicate early breakthrough behavior in parts of the profile. Groundtruthing with pore fluid conductivity and water content variations shows disagreement between expected and observed bulk conductivity. This was attributed to the different sampling volume of traditional methods and ERT due to a considerable fraction of immobile water in the soil. The results show that ERT can be used as a soil monitoring tool on airport sites if assisted by common soil monitoring techniques.
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Affiliation(s)
- Markus Wehrer
- Department of Earth and Environmental Sciences, Rutgers, The State University of New Jersey, 101 Warren Street, Smith Hall, Room 135, Newark, NJ, 07102, USA,
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Schotanus D, Meeussen JCL, Lissner H, van der Ploeg MJ, Wehrer M, Totsche KU, van der Zee SEATM. Transport and degradation of propylene glycol in the vadose zone: model development and sensitivity analysis. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2013; 21:9054-9066. [PMID: 24002660 DOI: 10.1007/s11356-013-2033-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Accepted: 07/22/2013] [Indexed: 06/02/2023]
Abstract
Transport and degradation of de-icing chemical (containing propylene glycol, PG) in the vadose zone were studied with a lysimeter experiment and a model, in which transient water flow, kinetic degradation of PG and soil chemistry were combined. The lysimeter experiment indicated that aerobic as well as anaerobic degradation occurs in the vadose zone. Therefore, the model included both types of degradation, which was made possible by assuming advection-controlled (mobile) and diffusion-controlled (immobile) zones. In the mobile zone, oxygen can be transported by diffusion in the gas phase. The immobile zone is always water-saturated, and oxygen only diffuses slowly in the water phase. Therefore, the model is designed in a way that the redox potential can decrease when PG is degraded, and thus, anaerobic degradation can occur. In our model, manganese oxide (MnO2, which is present in the soil) and NO3- (applied to enhance biodegradation) can be used as electron acceptors for anaerobic degradation. The application of NO3- does not result in a lower leaching of PG nor in a slower depletion of MnO2. The thickness of the snowcover influences the leached fraction of PG, as with a high infiltration rate, transport is fast, there is less time for degradation and thus more PG will leach. The model showed that, in this soil, the effect of the water flow dominates over the effect of the degradation parameters on the leaching at a 1-m depth.
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Affiliation(s)
- D Schotanus
- Soil Physics and Land Management, PO Box 47, 6700 AA, Wageningen, The Netherlands,
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