One of the key challenges of aqueous supercapacitors is the relatively low voltage (0.8–2.0 V), which significantly limits the energy density and feasibility of practical applications of the device. ...Herein, this study reports a novel Ni–Mn–O solid‐solution cathode to widen the supercapacitor device voltage, which can potentially suppress the oxygen evolution reaction and thus be operated stably within a quite wide potential window of 0–1.4 V (vs saturated calomel electrode) after a simple but unique phase‐transformation electrochemical activation. The solid‐solution structure is designed with an ordered array architecture and in situ nanocarbon modification to promote the charge/mass transfer kinetics. By paring with commercial activated carbon anode, an ultrahigh voltage asymmetric supercapacitor in neutral aqueous LiCl electrolyte is assembled (2.4 V; among the highest for single‐cell supercapacitors). Moreover, by using a polyvinyl alcohol (PVA)–LiCl electrolyte, a 2.4 V hydrogel supercapacitor is further developed with an excellent Coulombic efficiency, good rate capability, and remarkable cycle life (>5000 cycles; 95.5% capacity retention). Only one cell can power the light‐emitting diode indicator brightly. The resulting maximum volumetric energy density is 4.72 mWh cm−3, which is much superior to previous thin‐film manganese‐oxide‐based supercapacitors and even battery–supercapacitor hybrid devices.
A very simple but unique phase‐transformation electrochemical activation strategy is developed to enable a solid‐solution Ni–Mn–O nanoprism array to suppress the oxygen evolution and exhibit ultrawide stable electrochemical window (0–1.4 V vs saturated calomel electrode). With such as an array as the cathode, a 2.4 V ultrahigh voltage aqueous supercapacitor is constructed, demonstrating high volumetric energy/power densities.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Nano-Al-ethanol-based nanofluid fuel as a high-energy fuel has broad application prospects in the field of aviation vehicles. However, the detailed reaction mechanism of ethanol over the nano-Al ...surface is still a gray area. Hence, the adsorption and dissociation behaviors of ethanol molecule on the nano-Al (111) surface were investigated by a density functional theory calculation. Ethanol can be chemically adsorbed on the Al-top site by forming an Al–O bond. For ethanol dissociation, it can be dehydrogenated first to form ethoxy, acetaldehyde, and ethyl species, respectively. Then, ethoxy continues to dehydrogenate to generate acetaldehyde, ethylene oxide isomer, and formaldehyde. Finally, ethylene oxide can be dissociated to form formyl-methyl, formaldehyde, and ethylene species. Moreover, ethanol can also strip off both a hydrogen and a hydroxyl group concurrently to form ethylene. The generated acetaldehyde intermediate can be further decomposed into products such as acetyl, aldehyde group, and formyl-methyl species, which increase the variety of active substances of Al-ethanol based nanofluid fuel. This theoretical calculation provides a new insight for studying the decomposition mechanism of organic molecules in nanofluid fuels at the microscopic level.
Graphical abstract
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
To improve the deNOx and anti-poisoning performance of γ-Fe2O3 catalyst, the effects of three dopants Mn, Co, and Ce on gas adsorption and SO2 oxidation were investigated by a DFT method. Results ...show that NH3, NO, O2 can be adsorbed stably on the γ-Fe2O3 (001) surface to form coordinated NH3, nitrosyl, and adsorbed oxygen species, respectively. SO2 and H2O bind to Fe site on the catalyst surface by weak chemisorption. Doped Mn, Co, and Ce atoms simultaneously improve the gas adsorption performance of its own site and the surrounding Fe sites, especially for Ce doping. Furthermore, doping Mn contributes to the oxidation of SO2 to SO3, while doping Co and Ce restrains the formation of SO3, especially doping Ce, which is conducive to sulfur resistance of the catalyst. By comparison, the doping of Ce has more excellent deNOx and anti-poisoning property for the γ-Fe2O3 catalyst, which provides theoretical guidance for the selection of dopant in the subsequent experiments.
Display omitted
•The adsorption properties of NH3, NO, O2, SO2, and H2O molecules on the γ-Fe2O3 (001) surface were studied.•Doping Mn, Co, and Ce can improve the adsorption of gas molecules.•Doped atoms have a positive effect on the surrounding Fe atoms.•Doping Ce greatly restrains the oxidation of SO2.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Activated carbon supported iron-based catalysts (FexOy/AC) show good deNOx efficiency at low temperature. The doping of chromium (Cr) greatly improves the catalyst activity. However, the detailed ...effect of doping Cr over FexOy/AC surface at molecular level is still a grey area. In this study, the roles of Cr dopant on gas adsorption and NO oxidation were deeply investigated by a DFT-D3 method. Results show that the synergy of Cr–Fe bimetal improves the binding capacity of Fe2O3/AC and Fe3O4/AC surfaces after doping Cr. NH3 can be adsorbed on Cr and Fe sites to form coordinated NH3. Doping Cr greatly improves the NH3 adsorption property on the Fe3O4/AC surface. NO molecule can combine with Cr, Fe, and O sites to form nitrosyl and nitrite. The doping of Cr increases the adsorption performance of NO on the Fe2O3/AC and Fe3O4/AC surfaces, especially for Fe3O4/AC surface. Furthermore, NO can be oxidized to NO2 by adsorption oxygen or active O sites of FexOy clusters. The doping of Cr restrains the formation of insoluble chelating bidentate nitrates and greatly reduces the reaction energy barrier of NO oxidation on the FexOy/AC surface, which can promote the deNOx reaction.
Display omitted
•Doping Cr enhances the binding property of Fe2O3/AC and Fe3O4/AC system.•Doping Cr greatly improves NH3 and NO adsorption property on the Fe3O4/AC surface.•NO can be oxidized to NO2 based on adsorbed oxygen.•Doping Cr greatly reduces the energy barrier of NO oxidation.•Doping Cr restrains the formation of insoluble chelating bidentate nitrate.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The gas adsorption properties and NH3-SCR reaction mechanism over the Fe2O3/Ni(111) surface were investigated by a DFT-D study. The results show that the Fe2O3 cluster has more excellent gas ...adsorption performance than the Ni carrier. Single gas adsorption products are coordinated ammonia, nitroso, and adsorption oxygen, respectively. The presence of O2 promotes bimolecular adsorption. Three NH3-SCR reaction routes are revealed and mainly follow the Eley–Rideal mechanism. The reaction of NH3 and NO involves five steps: (1) NH3* dehydrogenation, (2) NH2NO* generation, (3) NHNO* generation, (4) NHNO* dissociation, and (5) H2O generation. NHNO* dissociation into N2 releases lots of energy. The reaction of O2 and NO eventually forms NO2, and is an energetically favorable process. Reaction of NO2 with NH3 involves three steps: (1) NH2NO2 generation, (2) NHNO2 generation, and (3) NHNO2 dissociation. NHNO2* decomposition and H2O* desorption as the rate-determining steps control the whole reaction rate. In addition, the reason for the high NOx conversion of “fast-SCR” is that NO2 reacts more easily with NH2 to form a nitrogen intermediate compared to NO.
Display omitted
•A new strategy of Cu doping was proposed to enhance the NH3-SCR activity of Fe-based catalyst at low temperature.•Cu dopant and oxygen vacancy synergistically promote the activity of ...Fe-based catalysts.•The doping of Cu promotes the formation of oxygen vacancy.•The NH3-SCR reaction mechanism of CuFe bimetallic catalysts was revealed.
In this work, we proposed a novel strategy of copper (Cu) doping to enhance the nitrogen oxides (NOx) removal efficiency of iron (Fe)-based catalysts at low temperature through a simple citric acid mixing method, which is critical for its practical application. The doping of Cu significantly improves the deNOx performance of Fe-based catalysts below 200 °C, and the optimal catalyst is (Cu0.22Fe1.78)1−δO3, which deNOx efficiency can reach 100% at 160–240 °C. From the macro aspects, the main reasons for the excellent catalytic activity of the (Cu0.22Fe1.78)1−δO3 catalyst are the large number of oxygen vacancies (Ovac), appropriate Fe3+ and Cu2+ contents, stronger surface acidity and redox ability. From the micro aspects, the Ovac plays a key role in enhancing molecular adsorption, oxidation, and the deNOx reaction over the Fe-based catalyst surface, which promoting order is CuOvac > Ovac > Cu. This work provides a new insight for the mechanism study of oxygen vacancy engineering and also accelerates the development of CuFe bimetal composite catalysts at low temperature.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The gas adsorption properties and NH
3
-SCR reaction mechanism over the Fe
2
O
3
/Ni(111) surface were investigated by a DFT-D study. The results show that the Fe
2
O
3
cluster has more excellent gas ...adsorption performance than the Ni carrier. Single gas adsorption products are coordinated ammonia, nitroso, and adsorption oxygen, respectively. The presence of O
2
promotes bimolecular adsorption. Three NH
3
-SCR reaction routes are revealed and mainly follow the Eley-Rideal mechanism. The reaction of NH
3
and NO involves five steps: (1) NH
3
* dehydrogenation, (2) NH
2
NO* generation, (3) NHNO* generation, (4) NHNO* dissociation, and (5) H
2
O generation. NHNO* dissociation into N
2
releases lots of energy. The reaction of O
2
and NO eventually forms NO
2
, and is an energetically favorable process. Reaction of NO
2
with NH
3
involves three steps: (1) NH
2
NO
2
generation, (2) NHNO
2
generation, and (3) NHNO
2
dissociation. NHNO
2
* decomposition and H
2
O* desorption as the rate-determining steps control the whole reaction rate. In addition, the reason for the high NO
x
conversion of "fast-SCR" is that NO
2
reacts more easily with NH
2
to form a nitrogen intermediate compared to NO.
The adsorption and SCR reaction mechanism of NH
3
, NO, and O
2
molecules on the Fe
2
O
3
/Ni(111) catalyst surface was revealed.
The gas adsorption properties and NH 3 -SCR reaction mechanism over the Fe 2 O 3 /Ni(111) surface were investigated by a DFT-D study. The results show that the Fe 2 O 3 cluster has more excellent gas ...adsorption performance than the Ni carrier. Single gas adsorption products are coordinated ammonia, nitroso, and adsorption oxygen, respectively. The presence of O 2 promotes bimolecular adsorption. Three NH 3 -SCR reaction routes are revealed and mainly follow the Eley–Rideal mechanism. The reaction of NH 3 and NO involves five steps: (1) NH 3 * dehydrogenation, (2) NH 2 NO* generation, (3) NHNO* generation, (4) NHNO* dissociation, and (5) H 2 O generation. NHNO* dissociation into N 2 releases lots of energy. The reaction of O 2 and NO eventually forms NO 2 , and is an energetically favorable process. Reaction of NO 2 with NH 3 involves three steps: (1) NH 2 NO 2 generation, (2) NHNO 2 generation, and (3) NHNO 2 dissociation. NHNO 2 * decomposition and H 2 O* desorption as the rate-determining steps control the whole reaction rate. In addition, the reason for the high NO x conversion of “fast-SCR” is that NO 2 reacts more easily with NH 2 to form a nitrogen intermediate compared to NO.
In order to reduce the cost of oxygen carriers, alkali metals (K, Na) are used to dope the deactivated Fe2O3/Al2O3 oxygen carrier, thus regenerating the redox activity of the deactivated oxygen ...carrier. In the case of adding the same molar amount, K could rapidly regenerate the redox performance of deactivated sample. After multiple cycles, the oxygen carrying capacity of deactivated sample doped by 5% K reached the highest oxygen carrying capacity of Fe2O3/Al2O3 before deactivation. The characterization results showed that the surface alkali metal diffused to the inside of the deactivated sample in the continuous cyclic reactions, thus forming a porous structure and then improving the gas-solid reactions in chemical looping combustion. XPS results indicated that the addition of alkali metal was beneficial to increase the content of surface adsorbed oxygen or oxygen vacancies of the deactivated Fe2O3/Al2O3. It strengthened the oxidation ability of the deactivated Fe2O3/Al2O3. In addition, the effect of K content on the regeneration of the deactivated Fe2O3/Al2O3 was also studied. The results showed that the optimum amount of K was 5%. Further increasing the amount of K had no significant effect on the regeneration of the deactivated Fe2O3/Al2O3.
Display omitted
•The addition of alkali metal help to the regeneration of the deactivated Fe2O3/Al2O3.•K can rapidly regenerate the redox performance of the deactivated Fe2O3/Al2O3.•The diffusion of alkali metal drive the regeneration of the deactivated Fe2O3/Al2O3.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The sluggish kinetics of Fe2+ regeneration seriously hinders the performance of Fenton process. However, the conventional Fenton system excessively stifle hydrogen-producing reactions, ignoring the ...significance of active hydrogen (H*) in Fe3+ reduction. Herein, a strategy of H* modulation is developed by decorating molybdenum disulfide (MoS2) on a graphite felt (GF) cathode to boost Fe2+ regeneration in solar-driven electro-Fenton (SEF) process. With MoS2 regulation, moderately dispersed MoS2 on GF can serve as a bifunctional cathode, where the H* and hydrogen peroxide (H2O2) are simultaneously generated through H+ reduction and O2 reduction, respectively. The in-situ generated H2O2 can trigger Fenton reactions with Fe2+, while the H* with robust reducing potential can significantly expedite Fe3+ reduction, consequently enhancing the HO• production. Both DFT calculations and EPR experiments confirm that H* can be activated via MoS2 decoration. The results show that Fe2+ concentration in the MoS2 @GF-SEF system remains at 15.74 mg/L (56.21%) after 6 h, which is 17.89 times that of the GF-SEF system. Moreover, the HO• content and organics degradation rate in the MoS2 @GF-SEF are 3.61 and 5.30 times those of the GF-SEF, respectively. This study provides a practical cathode strategy of H* modulation to enhance HO• production and electro-Fenton process.
Boosting Fe2+ regeneration is of great value for the Electro-Fenton process. Herein, report a strategy to achieve this goal based on a MoS2 @GF cathode. Remarkably, the MoS2 @GF system exhibits exceptional efficiency for both various refractory organic compounds with environmentally hazardous effects and sterilization aspects, which can also work over a wide range of pH values (3−11). Specially, this system is driven only by solar energy. These characteristics make the electro-Fenton system more suitable for practical wastewater treatment.
Display omitted
•A strategy of H* modulation is developed in solar-driven Electro-Fenton process.•H* is successfully introduced and modulated by MoS2 to boost Fe2+ regeneration.•The MoS2 @GF bifunctional cathode can simultaneously generate H2O2 and H*.•Both Fe2+ and HO• are boosted and maintained at a high level.•The Fenton system can also work over a wide range of pH values.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
