The platinum-group metals (PGMs) are six neighboring elements in the periodic table of the elements. Each PGM can efficiently promote unique reactions, and therefore, alloying PGMs would create ideal ...catalysts for complex or multistep reactions that involve several reactants and intermediates. Thus, high-entropy-alloy (HEA) nanoparticles (NPs) of all six PGMs (denoted as PGM-HEA) having a great variety of adsorption sites on their surfaces could be ideal candidates to catalyze complex reactions. Here, we report for the first time PGM-HEA and demonstrate that PGM-HEA efficiently promotes the ethanol oxidation reaction (EOR) with complex 12-electron/12-proton transfer processes. PGM-HEA shows 2.5 (3.2), 6.1 (9.7), and 12.8 (3.4) times higher activity than the commercial Pd/C, Pd black and Pt/C catalysts in terms of intrinsic (mass) activity, respectively. Remarkably, it records more than 1.5 times higher mass activity than the most active catalyst to date. Our findings pave the way for promoting complex or multistep reactions that are seldom realized by mono- or bimetallic catalysts.
Water is the only available fossil-free source of hydrogen. Splitting water electrochemically is among the most used techniques, however, it accounts for only 4% of global hydrogen production. One of ...the reasons is the high cost and low performance of catalysts promoting the oxygen evolution reaction (OER). Here, we report a highly efficient catalyst in acid, that is, solid-solution Ru‒Ir nanosized-coral (RuIr-NC) consisting of 3 nm-thick sheets with only 6 at.% Ir. Among OER catalysts, RuIr-NC shows the highest intrinsic activity and stability. A home-made overall water splitting cell using RuIr-NC as both electrodes can reach 10 mA cm
at 1.485 V for 120 h without noticeable degradation, which outperforms known cells. Operando spectroscopy and atomic-resolution electron microscopy indicate that the high-performance results from the ability of the preferentially exposed {0001} facets to resist the formation of dissolvable metal oxides and to transform ephemeral Ru into a long-lived catalyst.
Establishing new energy-saving systems for gas separation using porous materials is indispensable for ensuring a sustainable future. Herein, we show that ELM-11 (Cu(BF
)
(4,4'-bipyridine)
), a ...member of flexible metal-organic frameworks (MOFs), exhibits rapid responsiveness to a gas feed and an 'intrinsic thermal management' capability originating from a structural deformation upon gas adsorption (gate-opening). These two characteristics are suitable for developing a pressure vacuum swing adsorption (PVSA) system with rapid operations. A combined experimental and theoretical study reveals that ELM-11 enables the high-throughput separation of CO
from a CO
/CH
gas mixture through adiabatic operations, which are extreme conditions in rapid pressure vacuum swing adsorption. We also propose an operational solution to the 'slipping-off' problem, which is that the flexible MOFs cannot adsorb target molecules when the partial pressure of the target gas decreases below the gate-opening pressure. Furthermore, the superiority of our proposed system over conventional systems is demonstrated.
Refrigeration is of vital importance for modern society-for example, for food storage and air conditioning-and 25 to 30 per cent of the world's electricity is consumed for refrigeration
. Current ...refrigeration technology mostly involves the conventional vapour compression cycle, but the materials used in this technology are of growing environmental concern because of their large global warming potential
. As a promising alternative, refrigeration technologies based on solid-state caloric effects have been attracting attention in recent decades
. However, their application is restricted by the limited performance of current caloric materials, owing to small isothermal entropy changes and large driving magnetic fields. Here we report colossal barocaloric effects (CBCEs) (barocaloric effects are cooling effects of pressure-induced phase transitions) in a class of disordered solids called plastic crystals. The obtained entropy changes in a representative plastic crystal, neopentylglycol, are about 389 joules per kilogram per kelvin near room temperature. Pressure-dependent neutron scattering measurements reveal that CBCEs in plastic crystals can be attributed to the combination of extensive molecular orientational disorder, giant compressibility and highly anharmonic lattice dynamics of these materials. Our study establishes the microscopic mechanism of CBCEs in plastic crystals and paves the way to next-generation solid-state refrigeration technologies.
We report the synthesis of high-entropy-alloy (HEA) nanoparticles (NPs) consisting of five platinum group metals (Ru, Rh, Pd, Ir and Pt) through a facile one-pot polyol process. We investigated the ...electronic structure of HEA NPs using hard X-ray photoelectron spectroscopy, which is the first direct observation of the electronic structure of HEA NPs. Significantly, the HEA NPs possessed a broad valence band spectrum without any obvious peaks. This implies that the HEA NPs have random atomic configurations leading to a variety of local electronic structures. We examined the hydrogen evolution reaction (HER) and observed a remarkably high HER activity on HEA NPs. At an overpotential of 25 mV, the turnover frequencies of HEA NPs were 9.5 and 7.8 times higher than those of a commercial Pt catalyst in 0.05 M H
2
SO
4
and 1.0 M KOH electrolytes, respectively. Moreover, the HEA NPs showed almost no loss during a cycling test and were much more stable than the commercial Pt catalyst. Our findings on HEA NPs may provide a new paradigm for the design of catalysts.
RuRhPdIrPt high-entropy-alloy nanoparticles with a broad and featureless valence band spectrum show high hydrogen evolution reaction activity.
Bifunctional electrocatalysts for oxygen evolution/reduction reaction (OER/ORR) are desirable for the development of energy conversion technologies. It is discovered that the manganese quadruple ...perovskites CaMn7O12 and LaMn7O12 show bifunctional catalysis in the OER/ORR. A possible origin of the high OER activity is the unique surface structure through corner‐shared planar MnO4 and octahedral MnO6 units to promote direct OO bond formations.
We report novel PtW solid-solution nanoparticles (NPs) produced through electrochemical cleaning of core/shell PtW@WO3 NPs. The resulting PtW NPs achieved a record hydrogen evolution reaction (HER) ...performance as a class of Pt-based solid-solution alloys. A current density of 10 mA cm–2 was reached with an overpotential of 19.4 mV, which is significantly lower than that of a commercial Pt catalyst (26.3 mV). The PtW NPs also exhibited long-term stability. Theoretical calculations revealed that negatively charged Pt atoms adjacent to a W atom provide favorable hydrogen adsorption energies for the HER, realizing significantly enhanced HER activity.
Clarifying dynamic processes of materials is an important research topic in materials science. Time-resolved X-ray diffraction is a powerful technique for probing dynamic processes. To understand the ...dynamics, it is essential to analyze time-series data using appropriate time-evolution models and accurate start times of dynamic processes. However, conventional analyses based on non-linear least-squares fitting have difficulty both evaluating time-evolution models and estimating start times. Here, we establish a Bayesian framework including time-evolution models. We investigate an adsorption process, which is a representative dynamic process, and extract information about the time-evolution model and adsorption start time. The information enables us to estimate adsorption properties such as rate constants more accurately, thus achieving more precise understanding of dynamic adsorption processes. Our framework is highly versatile, can be applied to other dynamic processes such as chemical reactions, and is expected to be utilized in various areas of materials science.
Recently, there has been a high demand for elucidating kinetics and visualizing reaction processes under extreme dynamic conditions, such as chemical reactions under meteorite impact conditions, ...structural changes under nonequilibrium conditions, and in situ observations of dynamic changes. To accelerate material science studies and Earth science fields under dynamic conditions, a submillisecond in situ X‐ray diffraction measurement system has been developed using a diamond anvil cell to observe reaction processes under rapidly changing pressure and temperature conditions replicating extreme dynamic conditions. The development and measurements were performed at the high‐pressure beamline BL10XU/SPring‐8 by synchronizing a high‐speed hybrid pixel array detector, laser heating and temperature measurement system, and gas‐pressure control system that enables remote and rapid pressure changes using the diamond anvil cell. The synchronized system enabled momentary heating and rapid cooling experiments up to 5000 K via laser heating as well as the visualization of structural changes in high‐pressure samples under extreme dynamic conditions during high‐speed pressure changes.
A submillisecond X‐ray diffraction measurement system targeted at microscopic samples in a diamond anvil cell has been developed at BL10XU/SPring‐8. This system has enabled the visualization of structural changes of high‐pressure samples in the diamond anvil cell during instantaneous heating and quenching experiments combined with laser heating and during instantaneous compression and decompression experiments using a two‐line gas‐pressure control system, with a resolution in the submillisecond range.
Binary solid-solution alloys generally adopt one of three principal crystal lattices-body-centred cubic (bcc), hexagonal close-packed (hcp) or face-centred cubic (fcc) structures-in which the ...structure is dominated by constituent elements and compositions. Therefore, it is a significant challenge to selectively control the crystal structure in alloys with a certain composition. Here, we propose an approach for the selective control of the crystal structure in solid-solution alloys by using a chemical reduction method. By precisely tuning the reduction speed of the metal precursors, we selectively control the crystal structure of alloy nanoparticles, and are able to selectively synthesize fcc and hcp AuRu
alloy nanoparticles at ambient conditions. This approach enables us to design alloy nanomaterials with the desired crystal structures to create innovative chemical and physical properties.
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