Prussian blue analogs (PBAs) are used as electrode materials in energy storage and water deionization cells due to their reversible cation intercalation capability. Despite extensive research on their performance and intercalation mechanisms, little attention has been given to their behavior under open-circuit conditions. Recent studies using symmetrical PBA electrodes in two electrode deionization cells reported that after constant current cycling in dilute NaCl (<0.2 M), the cell voltage dropped under open-circuit conditions, which substantially increased the amount of energy consumed for deionization. However, it remains unclear which electrode (anode/cathode) experienced potential drift and if it was influenced by the low salinity of the electrolyte. Here, we performed a series of electrochemical experiments under different charging and discharging regimes and electrolyte compositions to determine the processes that contributed most significantly to open-circuit potential drift. The data indicated that charge redistribution within the electrode was the main contributor to open circuit potential drift, with electrode dissolution and parasitic reactions playing negligible roles. A one-dimensional finite element model was constructed to simulate charge redistribution by accounting for cation diffusion under open-circuit conditions. The open-circuit potential profiles generated by the model were validated against experimental trends, confirming the occurrence of charge redistribution. A Monte Carlo analysis of the model was conducted to determine the relationship of potential drift to key factors such as applied current, electrode thickness, diffusion coefficient of intercalating ions, and intercalation capacity. Subsequently, a dimensionless number (
- Award ID(s):
- 1900125
- NSF-PAR ID:
- 10396652
- Date Published:
- Journal Name:
- Physical Chemistry Chemical Physics
- Volume:
- 23
- Issue:
- 33
- ISSN:
- 1463-9076
- Page Range / eLocation ID:
- 17904 to 17916
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Da ) was developed based on the Dahmköhler number to relate the extent of potential drift resulting from combinations of these factors. The analyses revealed a strong positive correlation between simulated potential drift andDa . Among the key factors studied here, the diffusion coefficient and applied current had the largest impact onDa and, consequently, on potential drift. -
null (Ed.)Sr(Ti 0.3 Fe 0.7 )O 3−δ (STF) and the associated exsolution electrodes Sr 0.95 (Ti 0.3 Fe 0.63 Ru 0.07 )O 3−δ (STFR), or Sr 0.95 (Ti 0.3 Fe 0.63 Ni 0.07 )O 3−δ (STFN) are alternatives to Ni-based cermet fuel electrodes for solid oxide electrochemical cells (SOCs). They can provide improved tolerance to redox cycling and fuel impurities, and may allow direct operation with hydrocarbon fuels. However, such perovskite-oxide-based electrodes present processing challenges for co-sintering with thin electrolytes to make fuel electrode supported SOCs. Thus, they have been mostly limited to electrolyte-supported SOCs. Here, we report the first example of the application of perovskite oxide fuel electrodes in novel oxygen electrode supported SOCs (OESCs) with thin YSZ electrolytes, and demonstrate their excellent performance. The OESCs have La 0.8 Sr 0.2 MnO 3−δ –Zr 0.92 Y 0.16 O 2−δ (LSM–YSZ) oxygen electrode-supports that are enhanced via infiltration of SrTi 0.3 Fe 0.6 Co 0.1 O 3−δ , while the fuel electrodes are either Ni-YSZ, STF, STFN, or STFR. Fuel cell power density as high as 1.12 W cm −2 is obtained at 0.7 V and 800 °C in humidified hydrogen and air with the STFR electrode, 60% higher than the same cell made with a Ni-YSZ electrode. Electrolysis current density as high as −1.72 A cm −2 is obtained at 1.3 V and 800 °C in 50% H 2 O to 50% H 2 mode; the STFR cell yields a value 72% higher than the same cell made with a Ni-YSZ electrode, and competitive with the widely used conventional Ni-YSZ-supported cells. The high performance is due in part to the low resistance of the thin YSZ electrolyte, and also to the low fuel electrode polarization resistance, which decreases with fuel electrode in the order: Ni-YSZ > STF > STFN > STFR. The high performance of the latter two electrodes is due to exsolution of catalytic metal nanoparticles; the results are discussed in terms of the microstructure and properties of each electrode material, and surface oxygen exchange resistance values are obtained over a range of conditions for STF, STFN, and STFN. The STF fuel electrodes also provide good stability during redox cycling.more » « less
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Abstract Two-dimensional (2D) ternary materials recently generated interest in optoelectronics and energy-related applications, alongside their binary counterparts. To date, only a few naturally occurring layered 2D ternary materials have been explored. The plethora of benefits owed to reduced dimensionality prompted exploration of expanding non-layered ternary chalcogenides into the 2D realm. This work presents a templating method that uses 2D transition metal dichalcogenides as initiators to be converted into the corresponding ternary chalcogenide upon addition of copper, via a solution-phase synthesis, conducted in high boiling point solvents. The process starts with preparation of VSe2nanosheets, which are next converted into Cu3VSe4sulvanite nanosheets (NSs) which retain the 2D geometry while presenting an X-ray diffraction pattern identical with the one for the bulk Cu3VSe4. Both the scanning electron microscopy and transmission microscopy electron microscopy show the presence of quasi-2D morphology. Recent studies of the sulfur-containing sulvanite Cu3VS4highlight the presence of an intermediate bandgap, associated with enhanced photovoltaic (PV) performance. The Cu3VSe4nanosheets reported herein exhibit multiple UV–Vis absorption peaks, related to the intermediate bandgaps similar to Cu3VS4and Cu3VSe4nanocrystals. To test the potential of Cu3VSe4NSs as an absorber for solar photovoltaic devices, Cu3VSe4NSs thin-films deposited on FTO were subjected to photoelectrochemical testing, showing p-type behavior and stable photocurrents of up to ~ 0.036 mA/cm2. The photocurrent shows a ninefold increase in comparison to reported performance of Cu3VSe4nanocrystals. This proves that quasi-2D sulvanite nanosheets are amenable to thin-film deposition and could show superior PV performance in comparison to nanocrystal thin-films. The obtained electrical impedance spectroscopy signal of the Cu3VSe4 NSs-FTO based electrochemical cell fits an equivalent circuit with the circuit elements of solution resistance (Rs), charge-transfer resistance (Rct), double-layer capacitance (Cdl), and Warburg impedance (W). The estimated charge transfer resistance value of 300 Ω cm2obtained from the Nyquist plot provides an insight into the rate of charge transfer on the electrode/electrolyte interface.
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null (Ed.)Oxygen evolution reaction (OER) catalysts are critical components of photoanodes for photoelectrochemical (PEC) water oxidation. Herein, nanostructured metal boride MB (M = Co, Fe) electrocatalysts, which have been synthesized by a Sn/SnCl 2 redox assisted solid-state method, were integrated with WO 3 thin films to build heterojunction photoanodes. As-obtained MB modified WO 3 photoanodes exhibit enhanced charge carrier transport, amended separation of photogenerated electrons and holes, prolonged hole lifetime and increased charge carrier density. Surface modification of CoB and FeB significantly enhances the photocurrent density of WO 3 photoanodes from 0.53 to 0.83 and 0.85 mA cm −2 , respectively, in transient chronoamperometry (CA) at 1.23 V vs. RHE (V RHE ) under interrupted illumination in 0.1 M Na 2 SO 4 electrolyte (pH 7), corresponding to an increase of 1.6 relative to pristine WO 3 . In contrast, the pristine MB thin film electrodes do not produce noticeable photocurrent during water oxidation. The metal boride catalysts transform in situ to a core–shell structure with a metal boride core and a metal oxide (MO, M = Co, Fe) surface layer. When coupled to WO 3 thin films, the CoB@CoO x nanostructures exhibit a higher catalytic enhancement than corresponding pure cobalt borate (Co-B i ) and cobalt hydroxide (Co(OH) x ) electrocatalysts. Our results emphasize the role of the semiconductor–electrocatalyst interface for photoelectrodes and their high dependency on materials combination.more » « less
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Abstract Perovskites have emerged as a forerunner of electronics research due to their vast potential for optoelectronic applications. The numerous combinations of constituent ions and the potential for doping of perovskites lead to a high demand to track the underlying electronic properties. Solution‐based electrochemistry is particularly promising for detailed and facile assessment of perovskites. Here, electrochemical impedance spectroscopy (EIS) of methylammonium lead iodide (MAPbI3) thin films is performed and model them with an equivalent circuit that accounts for solvent, ionic, and thin film effects. A dielectric constant consistent with prior AC studies and a diffusion constant harmonious with cation motion in MAPbI3are extracted. An electrical double layer thickness in the perovskite film of 54 nm is obtained, consistent with lithium doping in perovskite films. Comparing the EIS and equivalent circuit model of perovskite films to control ITO‐only data enabled the assignment of the ions at each interface. This comparison implied a double layer of primarily lithium ions inside the perovskite film at the solution interface with significant recombination of ions on the solution side of the interface. This demonstrates EIS as a powerful tool for studying the fundamental charge accumulation and transport processes in perovskite thin films.
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D1CP02370E
