Shape control of inorganic nanocrystals is important for understanding basic size-and shape-dependent scaling laws and is useful in a wide range of applications. With minor modifications in the ...chemical environment, it is possible to control the reaction and diffusion processes at room temperature, opening up a synthetic route for the production of polymetallic hollow nanoparticles with very different morphology and composition, obtained by the simultaneous or sequential action of galvanic replacement and the Kirkendall effect.
Lithium–sulfur batteries (LSBs) are considered to be one of the most promising next generation energy storage systems due to their high energy density and low material cost. However, there are still ...some challenges for the commercialization of LSBs, such as the sluggish redox reaction kinetics and the shuttle effect of lithium polysulfides (LiPS). Here a 2D layered organic material, C2N, loaded with atomically dispersed iron as an effective sulfur host in LSBs is reported. X‐ray absorption fine spectroscopy and density functional theory calculations prove the structure of the atomically dispersed Fe/C2N catalyst. As a result, Fe/C2N‐based cathodes demonstrate significantly improved rate performance and long‐term cycling stability. Fe/C2N‐based cathodes display initial capacities up to 1540 mAh g−1 at 0.1 C and 678.7 mAh g−1 at 5 C, while retaining 496.5 mAh g−1 after 2600 cycles at 3 C with a decay rate as low as 0.013% per cycle. Even at a high sulfur loading of 3 mg cm−2, they deliver remarkable specific capacity retention of 587 mAh g−1 after 500 cycles at 1 C. This work provides a rational structural design strategy for the development of high‐performance cathodes based on atomically dispersed catalysts for LSBs.
A novel atomically dispersed catalyst prepared by loading iron atoms into a 2D organic layered material (C2N) is shown. C2N has abundant holes and pyrazine nitrogen in its structure. The Fe2N6 coordination structure is shown to work as an efficient active site in the cathode of lithium–sulfur batteries for promoting reversible electrochemical conversion during charging and discharging.
The overriding obstacle to mass production of hydrogen from water as the premium fuel for powering our planet is the frustratingly slow kinetics of the oxygen evolution reaction (OER). Additionally, ...inadequate understanding of the key barriers of the OER is a hindrance to insightful design of advanced OER catalysts. This study presents ultrathin amorphous high‐surface area nickel boride (NixB) nanosheets as a low‐cost, very efficient and stable catalyst for the OER for electrochemical water splitting. The catalyst affords 10 mA cm−2 at 0.38 V overpotential during OER in 1.0 m KOH, reducing to only 0.28 V at 20 mA cm−2 when supported on nickel foam, which ranks it among the best reported nonprecious catalysts for oxygen evolution. Operando X‐ray absorption fine‐structure spectroscopy measurements reveal prevalence of NiOOH, as well as Ni‐B under OER conditions, owing to a Ni‐B core@nickel oxyhydroxide shell (Ni‐B@NiOxH) structure, and increase in disorder of the NiOxH layer, thus revealing important insight into the transient states of the catalyst during oxygen evolution.
Ultrathin high‐surface area nickel boride nanosheets supported on nickel foam show outstanding activity in catalyzing the oxygen evolution reaction, ranking among the best nonprecious catalysts for oxygen evolution reported to date.
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•Optimal catalyst formulation can differ from plasma and thermal processes.•CO and CO2 hydrogenation are both parallel reaction pathways in DBD plasma-catalysis.•In CeO2-Ni-Al2O3, a ...significant lower amount of CeO2 is required for reaching a high yield of methane in plasma-catalysis.•At a high CeO2 loadings, the rate determining step of methanation is similar in both plasma and non-plasma processes.
The effect of Ce loading content on Ni-CeO2/Al2O3 catalysts for CO2 plasma methanation was evaluated. Catalysts were prepared by one-pot evaporation-induced self-assembly, Ni content was fixed at 15 wt. %, while CeO2 ranged 0–50 wt. %. The catalysts performances were tested under atmospheric pressure in two operation modes, thermal- and plasma-catalysis. As for conventional thermal catalysis, the catalyst was thermally activated between 200 and 400 °C; while in plasma-catalysis, the catalyst was activated by plasma generated by a dielectric barrier discharges (DBD) reactor. By the application of plasma in the catalyst bed, the reaction temperature was reduced from 350 °C to 150 °C to obtain the same level of conversion than thermal-catalysis. In addition, the incorporation of Ce in Ni-CeO2/Al2O3 led to an improvement of the catalytic performance in both thermal- and plasma-catalysis. Nevertheless, divergences on the optimum Ce content were found. On plasma experiments, the catalyst was more active at a lower amount of CeO2 (˜10 wt.%) with respect to thermal catalysis (˜40 wt.%), reducing the catalyst fabrication cost. Those differences highlights that the CO generated by plasma CO2 dissociation has a significant role for methane production, and thus the need to consider the by-products as reactant for the optimization of catalysts composition for DBD plasma-catalysis.
Cobalt phosphides electrocatalysts have great potential for water splitting, but the unclear active sides hinder the further development of cobalt phosphides. Wherein, three different cobalt ...phosphides with the same hollow structure morphology (CoP‐HS, CoP2‐HS, CoP3‐HS) based on the same sacrificial template of ZIF‐67 are prepared. Surprisingly, these cobalt phosphides exhibit similar OER performances but quite different HER performances. The identical OER performance of these CoPx‐HS in alkaline solution is attributed to the similar surface reconstruction to CoOOH. CoP‐HS exhibits the best catalytic activity for HER among these CoPx‐HS in both acidic and alkaline media, originating from the adjusted electronic density of phosphorus to affect absorption–desorption process on H. Moreover, the calculated ΔGH* based on P‐sites of CoP‐HS follows a quite similar trend with the normalized overpotential and Tafel slope, indicating the important role of P‐sites for the HER process. Moreover, CoP‐HS displays good performance (cell voltage of 1.67 V at a current density of 50 mA cm−2) and high stability in 1 M KOH. For the first time, this work detailly presents the critical role of phosphorus in cobalt‐based phosphides for water splitting, which provides the guidance for future investigations on transition metal phosphides from material design to mechanism understanding.
This work firstly reveals the critical role of phosphorus in cobalt‐based phosphides for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The phenomenon that cobalt‐based phosphides exhibit similar OER performances but quite different HER performances has been in‐depth analyzed. This work provides the guidance for the future investigations on transition metal phosphides for water splitting.
Abstract
Earth-abundant electrocatalysts for the oxygen evolution reaction (OER) able to work in acidic working conditions are elusive. While many first-row transition metal oxides are competitive in ...alkaline media, most of them just dissolve or become inactive at high proton concentrations where hydrogen evolution is preferred. Only noble-metal catalysts, such as IrO
2
, are fast and stable enough in acidic media. Herein, we report the excellent activity and long-term stability of Co
3
O
4
-based anodes in 1 M H
2
SO
4
(pH 0.1) when processed in a partially hydrophobic carbon-based protecting matrix. These Co
3
O
4
@C composites reliably drive O
2
evolution a 10 mA cm
–2
current density for >40 h without appearance of performance fatigue, successfully passing benchmarking protocols without incorporating noble metals. Our strategy opens an alternative venue towards fast, energy efficient acid-media water oxidation electrodes.
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