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.
Spin qubits are considered to be among the most promising candidates for building a quantum processor. Group IV hole spin qubits are particularly interesting owing to their ease of operation and ...compatibility with Si technology. In addition, Ge offers the option for monolithic superconductor–semiconductor integration. Here, we demonstrate a hole spin qubit operating at fields below 10 mT, the critical field of Al, by exploiting the large out-of-plane hole g-factors in planar Ge and by encoding the qubit into the singlet-triplet states of a double quantum dot. We observe electrically controlled g-factor difference-driven and exchange-driven rotations with tunable frequencies exceeding 100 MHz and dephasing times of 1 μs, which we extend beyond 150 μs using echo techniques. These results demonstrate that Ge hole singlet-triplet qubits are competing with state-of-the-art GaAs and Si singlet-triplet qubits. In addition, their rotation frequencies and coherence are comparable with those of Ge single spin qubits, but singlet-triplet qubits can be operated at much lower fields, emphasizing their potential for on-chip integration with superconducting technologies.A singlet-triplet spin qubit using holes in a Ge quantum well is demonstrated, and can be operated at low magnetic fields of a few millitesla.
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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.
Transition metal phosphides have great potential to optimize a number of functionalities in several energy conversion and storage applications, particularly when nanostructured or in nanoparticle ...form. However, the synthesis of transition metal phosphide nanoparticles and its scalability is often limited by the toxicity, air sensitivity, and high cost of the reagents used. We present here a simple, scalable, and cost-effective “heating up” procedure to produce metal phosphides using inexpensive, low-toxicity, and air-stable triphenyl phosphite as source of phosphorus and chlorides as metal precursors. This procedure allows the synthesis of a variety of phosphide nanoparticles, including phosphides of Ni, Co, and Cu. The use of carbonyl metal precursors further allowed the synthesis of Fe2P and MoP nanoparticles. The fact that minor modifications in the experimental parameters allowed producing nanoparticles with different compositions and even to tune their size and shape shows the high potential and versatility of the triphenyl phosphite precursor and the presented method. We also detail here a methodology to displace organic ligands from the surface of phosphide nanoparticles, which is a key step toward their application in energy conversion and storage systems.
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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