Superlattices are rising stars on the horizon of energy storage and conversion, bringing new functionalities; however, their complex synthesis limits their large‐scale production and application. ...Herein, a simple solution‐based method is reported to produce organic–inorganic superlattices and demonstrate that the pyrolysis of the organic compound enables tuning their interlayer space. This strategy is exemplified here by combining polyvinyl pyrrolidone (PVP) with WSe2 within PVP/WSe2 superlattices. The annealing of such heterostructures results in N‐doped graphene/WSe2 (NG/WSe2) superlattices with a continuously adjustable interlayer space in the range from 10.4 to 21 Å. Such NG/WSe2 superlattices show a metallic electronic character with outstanding electrical conductivities. Both experimental results and theoretical calculations further demonstrate that these superlattices are excellent sulfur hosts at the cathode of lithium–sulfur batteries (LSB), being able to effectively reduce the lithium polysulfide shuttle effect by dual‐adsorption sites and accelerating the sluggish Li–S reaction kinetics. Consequently, S@NG/WSe2 electrodes enable LSBs characterized by high sulfur usages, superior rate performance, and outstanding cycling stability, even at high sulfur loadings, lean electrolyte conditions, and at the pouch cell level. Overall, this work not only establishes a cost‐effective strategy to produce artificial superlattice materials but also pioneers their application in the field of LSBs.
N‐doped graphene/WSe2 (NG/WSe2) superlattice obtained by a cost‐effective synthetic strategy is used as a sulfur host to regulate lithium polysulfide (LiPS) conversion reaction. The increased interlayer spacing (1.04 nm) and enhanced conductivity guarantee the ion and electron transfer in Li–S reaction process, and the heterogeneous interface probes strong lithio/sulfiphilic dual‐adsorption sites to confine the LiPS shuttle effect. Consequently, robust lithium–sulfur batteries are obtained.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The development of upscalable oxygen evolving electrocatalysts from earth-abundant metals able to operate in neutral or acidic environments and low overpotentials remains a fundamental challenge for ...the realization of artificial photosynthesis. In this study, we report a highly active phase of heterobimetallic cyanide-bridged electrocatalysts able to promote water oxidation under neutral, basic (pH < 13), and acidic conditions (pH > 1). Cobalt–iron Prussian blue-type thin films, formed by chemical etching of Co(OH)1.0(CO3)0.5·nH2O nanocrystals, yield a dramatic enhancement of the catalytic performance toward oxygen production, when compared with previous reports for analogous materials. Electrochemical, spectroscopic, and structural studies confirm the excellent performance, stability, and corrosion resistance, even when compared with state-of-the-art metal oxide catalysts under moderate overpotentials and in a remarkably large pH range, including acid media where most cost-effective water oxidation catalysts are not useful. The origin of the superior electrocatalytic activity toward water oxidation appears to be in the optimized interfacial matching between catalyst and electrode surface obtained through this fabrication method.
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IJS, KILJ, NUK, PNG, UL, UM
Innovative bimetallic MOFs offer more possibilities to further tailor the properties of MOFs, which have attracted great attention for wide applications. However, it is still a great challenge to ...rationally design bimetallic MOFs due to the lack of a tunable and reasonable hybrid structure architecture. Herein, a new series of bimetallic metal–organic frameworks (MOFs) with tunable pillar linkers were prepared by a one-step synthesis method. These bimetallic MOFs retain the same crystal structure when the mole fraction (based on metal) of the two metals changes from 0 to 1 and both metal ions occupy random nodal positions. The incorporation of a second metal cation has a large influence on the intrinsic properties (
e.g.
thermal stabilities and band gaps) of the MOFs. Furthermore, these bimetallic MOFs were used as self-sacrificial templates to prepare bimetal oxide catalysts for the oxygen evolution reaction (OER). After pyrolysis, a porous and hierarchical honeycomb-like structure with carbon network covered (bi)metal oxides is formed. Among all the bimetallic MOF-derived catalysts, CoNi1@C showed the best performance for the OER with the lowest Tafel slopes (55.6 mV dec
−1
) and overpotentials (335 mV on a glassy carbon electrode and 276 mV on Ni foam) at a current density of 10 mA cm
−2
, which is higher than those of state-of-the-art Co–Ni mixed oxide catalysts derived from MOFs for the OER. Our results indicate that the incorporation of a second metal ion is a promising strategy to tailor the properties of MOFs. More importantly, this new bimetallic MOF family with tunable linkers is expected to serve as a flexible assembly platform to offer broad possibilities for practical applications of MOFs.
The shuttle effect and sluggish conversion kinetics of lithium polysulfides (LiPS) hamper the practical application of lithium–sulfur batteries (LSBs). Toward overcoming these limitations, herein an ...in situ grown C2N@NbSe2 heterostructure is presented with remarkable specific surface area, as a Li–S catalyst and LiPS absorber. Density functional theory (DFT) calculations and experimental results comprehensively demonstrate that C2N@NbSe2 is characterized by a suitable electronic structure and charge rearrangement that strongly accelerates the LiPS electrocatalytic conversion. In addition, heterostructured C2N@NbSe2 strongly interacts with LiPS species, confining them at the cathode. As a result, LSBs cathodes based on C2N@NbSe2/S exhibit a high initial capacity of 1545 mAh g−1 at 0.1 C. Even more excitingly, C2N@NbSe2/S cathodes are characterized by impressive cycling stability with only 0.012% capacity decay per cycle after 2000 cycles at 3 C. Even at a sulfur loading of 5.6 mg cm−2, a high areal capacity of 5.65 mAh cm−2 is delivered. These results demonstrate that C2N@NbSe2 heterostructures can act as multifunctional polysulfide mediators to chemically adsorb LiPS, accelerate Li‐ion diffusion, chemically catalyze LiPS conversion, and lower the energy barrier for Li2S precipitation/decomposition, realizing the “adsorption‐diffusion‐conversion” of polysulfides.
Heterostructured C2N@NbSe2 composites with high specific surface area and adjusted interface electronic structure are demonstrated as excellent catalysts in lithium–sulfur batteries (LSBs). The promoted adsorption capacity and catalytic effect are fully proved by experiments and theoretical calculation, and batteries based on the C2N@NbSe2/S cathode with exceptional lifespan are delivered.
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The shuttling behavior and sluggish conversion kinetics of intermediate lithium polysulfides (LiPS) represent the main obstacles to the practical application of lithium–sulfur batteries (LSBs). ...Herein, an innovative sulfur host is proposed, based on an iodine‐doped bismuth selenide (I‐Bi2Se3), able to solve these limitations by immobilizing the LiPS and catalytically activating the redox conversion at the cathode. The synthesis of I‐Bi2Se3 nanosheets is detailed here and their morphology, crystal structure, and composition are thoroughly. Density‐functional theory and experimental tools are used to demonstrate that I‐Bi2Se3 nanosheets are characterized by a proper composition and micro‐ and nano‐structure to facilitate Li+ diffusion and fast electron transportation, and to provide numerous surface sites with strong LiPS adsorbability and extraordinary catalytic activity. Overall, I‐Bi2Se3/S electrodes exhibit outstanding initial capacities up to 1500 mAh g−1 at 0.1 C and cycling stability over 1000 cycles, with an average capacity decay rate of only 0.012% per cycle at 1 C. Besides, at a sulfur loading of 5.2 mg cm−2, a high areal capacity of 5.70 mAh cm−2 at 0.1 C is obtained with an electrolyte/sulfur ratio of 12 µL mg−1. This work demonstrated that doping is an effective way to optimize the metal selenide catalysts in LSBs.
An innovative sulfur host, based on an iodine doped bismuth selenide (I‐Bi2Se3), is demonstrated as a multifunctional polysulfide mediator by immobilizing the LiPS and catalytically activating the redox conversion. The promoted adsorption capacity and catalytic effect are confirmed by experiments and theoretical calculations; thus, batteries with exceptional lifespan are delivered.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Urchin‐shaped NiCo2Se4 (u‐NCSe) nanostructures as efficient sulfur hosts are synthesized to overcome the limitations of lithium–sulfur batteries (LSBs). u‐NCSe provides a beneficial hollow structure ...to relieve volumetric expansion, a superior electrical conductivity to improve electron transfer, a high polarity to promote absorption of lithium polysulfides (LiPS), and outstanding electrocatalytic activity to accelerate LiPS conversion kinetics. Owing to these excellent qualities as cathode for LSBs, S@u‐NCSe delivers outstanding initial capacities up to 1403 mAh g−1 at 0.1 C and retains 626 mAh g−1 at 5 C with exceptional rate performance. More significantly, a very low capacity decay rate of only 0.016% per cycle is obtained after 2000 cycles at 3 C. Even at high sulfur loading (3.2 mg cm−2), a reversible capacity of 557 mAh g−1 is delivered after 600 cycles at 1 C. Density functional theory calculations further confirm the strong interaction between NCSe and LiPS, and cytotoxicity measurements prove the biocompatibility of NCSe. This work not only demonstrates that transition metal selenides can be promising candidates as sulfur host materials, but also provides a strategy for the rational design and the development of LSBs with long‐life and high‐rate electrochemical performance.
Rationally designed urchin‐shaped NiCo2Se4 (u‐NCSe) nanostructures as efficient sulfur hosts are synthesized to overcome the barriers of lithium–sulfur batteries simultaneously. Benefiting from a hollow structure to relieve volumetric expansion, superior electrical conductivity to improve electron transfer, high polarity to promote absorption of lithium polysulfides (LiPS), and outstanding electrocatalytic activity to accelerate LiPS conversion kinetics, S@u‐NCSe electrodes deliver long‐life and high‐rate electrochemical performance.
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•Production of SNG at MW scale is now technically feasible.•Estimated production costs of synthetic natural gas are 70–125 EUR/MWh, not competitive with current fossil natural ...gas.•Electrolysis efficiency and methanation capex costs are key factors to reduce the cost to 40 EUR/MWh.•An important reduction of the SNG production costs can be obtained by oxygen trading.•Synthetic natural gas is promising in continuous and seasonal production.
Power-to-Gas is a chemical energy storage technology based on converting electrical energy into chemical energy in the form of a certain gas, typically hydrogen or methane. The main advantage of methane, namely synthetic natural gas (SNG), is that in this way the already existing gas infrastructure can be used as transport and storage medium. This article evaluates the economic viability of SNG production from CO2 capture and utilization. As representative examples, California, Ontario, Spain, Sweden, Paraguay, Germany and India electricity markets were considered. At present, the estimated cost of SNG is 70–125 EUR/MWh, from 2 to 7 times higher than fossil natural gas. In a feasible future scenario, the costs can be reduced to 40 EUR/MWh, competing directly with the fossil fuel, especially in countries where it is mainly imported as Germany or Spain. To achieve this goal, further R&D is needed, especially on two key parameters: electrolysis efficiency and methanation capex costs. In any case, the economic viability of SNG is subject to high annual operating hours in order to return the initial investment. Therefore, the SNG process, rather than an intermittent grid storage technology, seems a promising in continuously or seasonal production, having a unique niche market among energy storage technologies.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The shuttle effect and the sluggish reaction kinetics of lithium polysulfide (LiPS) seriously compromise the performance of lithium–sulfur batteries (LSBs). To overcome these limitations and enable ...the fabrication of robust LSBs, here the use of a Mott–Schottky catalyst based on bimetallic phosphide CoFeP nanocrystals supported on carbon nitride tubular nanostructures as sulfur hosts is proposed. Theoretical calculations and experimental data confirm that CoFeP@CN composites are characterized by a suitable electronic structure and charge rearrangement that allows them to act as a Mott–Schottky catalyst to accelerate LiPS conversion. In addition, the tubular geometry of CoFeP@CN composites facilitates the diffusion of Li ions, accommodates volume change during the reaction, and offers abundant lithiophilic/sulfiphilic sites to effectively trap soluble LiPS. Therefore, S@CoFeP@CN electrodes deliver a superior rate performance of 630 mAh g−1 at 5 C, and remarkable cycling stability with 90.44% capacity retention over 700 cycles. Coin cells with high sulfur loading, 4.1 mg cm−2, and pouch cells with 0.1 Ah capacities are further produced to validate their superior cycling stability. In addition, it is demonstrated here that CoFeP@CN hosts greatly alleviate the often overlooked issues of low energy efficiency and serious self‐discharging in LSBs.
Bimetallic phosphide CoFeP nanocrystals are supported on carbon nitride tubular (t‐CN) nanostructures as a Mott–Schottky catalyst to regulate the lithium polysulfide (LiPS) conversion reaction. The built‐in electric field at the CoFeP/t‐CN interphase significantly promotes catalytic activity, abundant lithiophilic/sulfiphilic sites effectively trap soluble LiPS, and tubular geometry adequately accommodates volume change during the reaction. Consequently, robust lithium–sulfur batteries are obtained.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The conversion of carbon dioxide (CO2) into value-added chemicals and fuels, preferably using renewable energy and earth-abundant materials, is considered a key priority for future energy research. ...In this work, a bias-free reactor device for the solar-driven conversion of CO2 to synthesis gas (syngas) has been developed. The integrated fluidic device consists of a cathode made of copper foam coated with low-cost nanosized zinc flakes as catalyst to perform the CO2 reduction reaction (CO2RR) to syngas, an adapted silicon heterojunction solar cell structure as photoanode with nickel foam as catalyst to facilitate the oxygen evolution reaction (OER), and a bipolar membrane separating the respective catholyte and anolyte compartments. The membrane allows for the operation of the catholyte and anolyte at different pH values. Stable and tunable hydrogen-to-carbon monoxide (H2:CO) ratios between 5 and 0.5 along with high CO Faradaic efficiencies of up to 85% and CO current densities of 39.4 mA cm-2 have been demonstrated. Under photoelectrolysis conditions, the photovoltage of the photoanode was varied between 0.6 V and 2.4 V by connecting up to four heterojunction solar cells in series, and thus reducing the overall cell voltage solely by solar energy utilization. Bias-free operation of the integrated device has been achieved under ambient conditions with active areas for CO2RR and OER, respectively, of 10 cm2. An operation current density of 5.0 mA cm-2 was measured under 100 mW cm-2 illumination of the complete device, which corresponds to a solar-to-syngas conversion efficiency of 4.3%.
The design of the earth‐abundant, nonprecious, efficient, and stable electrocatalysts for efficient hydrogen evolution reaction (HER) in alkaline media is a hot research topic in the field of ...renewable energies. A heterostructured system composed of MoSx deposited on NiO nanostructures (MoSx@NiO) as a robust catalyst for water splitting is proposed here. NiO nanosponges are applied as cocatalyst for MoS2 in alkaline media. Both NiO and MoS2@NiO composites are prepared by a hydrothermal method. The NiO nanostructures exhibit sponge‐like morphology and are completely covered by the sheet‐like MoS2. The NiO and MoS2 exhibit cubic and hexagonal phases, respectively. In the MoSx@NiO composite, the HER experiment in 1 m KOH electrolyte results in a low overpotential (406 mV) to produce 10 mA cm−2 current density. The Tafel slope for that case is 43 mV per decade, which is the lowest ever achieved for MoS2‐based electrocatalyst in alkaline media. The catalyst is highly stable for at least 13 h, with no decrease in the current density. This simple, cost‐effective, and environmentally friendly methodology can pave the way for exploitation of MoSx@NiO composite catalysts not only for water splitting, but also for other applications such as lithium ion batteries, and fuel cells.
A heterostructured system composed of MoSx on NiO nanosponges is proposed as a robust catalyst for water splitting. The hydrogen evolution reaction in 1 m KOH electrolyte resulted in a low overpotential (406 mV) to produce a 10 mA cm−2 current density. The Tafel slope is 43 mV per decade, the lowest ever achieved for MoS2‐based electrocatalyst in alkaline media.
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