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CuInP2S6 (CIPS) is an emerging 2D ferroelectric material known for disrupting spatial inversion symmetry due to Cu(I) position switching. Its ferroelectricity strongly relies on the Cu(I) atom/ion occupation ordering and dynamics. Nevertheless, the accurate Cu(I) occupations and correlated migration dynamics under the externally applied energy, which are key to unlocking ferroelectric properties, remain controversial and unresolved. Herein, an atomic-level direct imaging through aberration-corrected scanning transmission electron microscopy is performed to precisely trace the Cu(I) dynamic behaviours under electron-beam irradiation along (100)-CIPS. It clearly demonstrates that Cu(I) possesses multiple occupations, and Cu(I) could migrate to the lattice, vacancy, interstitial and interlayer sites between the InS6 octahedral skeletons of CIPS to form local CuxInP2S6 (x = 2-4) structure. Cu(I) multi-occupations induced lattice stress results in a layer sliding along the b-axis direction generating a sliding size of 1/6 b lattice constant. The CuxInP2S6 (x = 2-4) exists in a type of dynamic structure, only metastable with electron dose over 50 e− Å−2, thus generating a dynamic process of C u x In P 2 S 6 (x = 2 − 4) ⇌ CuIn P 2 S 6 , a completely unreported phenomenon. These findings shed light on the unveiled mechanism underlying Cu(I) migration in CIPS, providing crucial insights into the fundamental processes that govern its ferroelectric properties. The authors demonstrate that Cu(I) possesses multiple occupations, and Cu(I) migrate to the lattice, vacancy, interstitial and interlayer sites between the InS6 octahedral skeletons of CuInP2S6 to form local CuxInP2S6 (x = 2-4) structure. [ABSTRACT FROM AUTHOR]

Catalysts that can promote the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) are in demand for efficient water splitting. Here, a general and practical UV‐induced synthesis of noble metal catalysts supported on reduced electrochemical graphene oxide (M‐rEGO, M = Ir, Pt or Pd) is proposed. The use of EGO with a low degree of oxidation and the generation of the highly reducing isopropanol radical from added isopropanol and acetone are crucial for this one‐step, one‐pot synthesis. Using Ir as a model material, the vacancies of rEGO allow the interaction of undercoordinated C with Ir, forming multiple active Ir species including single atoms (SAs), dual‐atom pairs (DAs) and nanoparticles. This Ir‐rEGO catalyst exhibits overpotentials of only 42.3 and 294 mV to reach 10 mA cm−2 in 0.5 м H2SO4 for HER and 1 м KOH for OER, respectively, at an extremely low Ir loading (2.1 wt%). The water‐splitting cells featuring Ir‐rEGO catalyst outperform those using commercial Pt/C (20 wt%) and RuO2 catalysts in both acidic and alkaline electrolytes. Density functional theory calculations confirm the stabilization of SAs and DAs at the vacancies of graphene lattice as well as the high activity of DAs in both HER and OER. [ABSTRACT FROM AUTHOR]

Seawater desalination is the most promising solution to a sustainable water future. However, state-of-the-art desalination technologies suffer from energy intensiveness and high capital expenditure. To address these issues, we have developed a novel, membrane-less desalination battery comprising negatively charged redox-active electrodes. A two-dimensional (2D) Ni and Co bimetallic metal–organic framework anchored on a black phosphorus nanosheet (NiCo MOF@BP) composite with fast sodium ion transport kinetics and favourable redox potentials for sodiation/desodiation when coupled with reduced graphene oxide supported silver nanoparticles (Ag@rGO) is applied. The incorporation of black phosphorus stabilizes the NiCo MOF and improves the overall electrical conductivity. Ultrastable cycling (46.5 mA h g−1 after over 1000 cycles in 2 M NaCl solution and 33.4 mA h g−1 after over 500 cycles in synthetic seawater at 0.3 A g−1) and rate performance (25.7 mA h g−1 at 2.5 A g−1) are realised. Besides, a high coulombic efficiency of 96.9% and superb energy recovery of 70.7% are achieved. As such, a low energy consumption of 0.034 W h g−1 with a salt removal capacity of 103.1 mg g−1 is obtained using synthetic seawater as the electrolyte, which is among the lowest in energy consumption when compared with other similar desalination technologies. The exploration of this novel cathode material paves the way for future material selection for desalination batteries. [ABSTRACT FROM AUTHOR]

A faradaic reaction-enhanced membrane capacitive deionization (MCDI) system has recently been proposed for the desalination of seawater owing to its superior salt removal capacity, lower energy consumption and applicability in high-salinity water. However, the detailed mechanism of the effect of the faradaic reaction on the desalination performance of an MCDI system in the constant voltage (CV) and constant current (CC) operational modes has been rarely studied. Herein, we systematically studied the faradaic reaction in an MCDI system in the CV and CC operational modes based on carbon cloth, Li4Ti5O12 nanoflake array (LTO NFA), and carbon-coated Li4Ti5O12 nanoflake array (LTO@C NFA) electrodes; the XPS and ex situ XRD results verified the intercalation of sodium ions in different operational modes. Upon the introduction of the faradaic mechanism, the desalination capacity (DC) of the MCDI system was no longer limited by the surface area of the electrodes since the salt ions could intercalate into the bulk material in addition to being adsorbed by electrical double layers (EDLs). A high DC of 25 mg g−1 after over 30 cycles in the CC mode has been achieved, exceeding that of the carbon cloth without faradaic reactions by 300%. The unique combination of the CC operational mode and the faradic electrodes provides a new perspective for the design of high-efficiency electrodes for advanced CDI. [ABSTRACT FROM AUTHOR]

The combination of different elements in alloy catalysts can lead to improved activity as it provides opportunities to tune the electronic structures of surface atoms. However, the synthesis and performance screening of alloy catalysts through a vast chemical space are cost- and labor-intensive. Herein, a UV-induced, high-throughput method is reported for the synthesis and screening of alloy electrocatalysts in a fast and low-cost manner. A platform that integrates 37 mini-reaction-cells enables simultaneous UV-induced photodeposition of alloy nanoparticles with up to 37 compositions. These mini-reaction-cells further allow a transfer-free, high-throughput electrochemical performance screening. Binary (PtPd, PtIr, PdIr), ternary (PtPdIr, PtRuIr) and quaternary (PtPdRuIr) alloys have been synthesized with the activity of the binary alloys (57 compositions) for hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) being screened. The predicted high performance of identified alloy compositions are subsequently validated by standard measurements using a rotating disk electrode configuration. It is found that the as-synthesized alloy nanoparticles are rich in twin boundaries and thus possess lattice strain. Density functional theory calculation implies that the high ORR activity of the screened Pt 0.75 Pd 0.25 alloy originates from the interplay between the differentiated adsorption sites because of alloying and the strain-induced modulation of the d-band center., (© 2024 Wiley‐VCH GmbH.)

The growth of entirely synthetic two-dimensional (2D) materials could further expand the library of naturally occurring layered solids and provide opportunities to design materials with finely tunable properties. Among them, the synthesis of elemental 2D materials is of particular interest as they represent the chemically simplest case and serve as a model system for exploring the on-surface synthesis mechanism. Here, a pure atomically thin blue phosphorus (BlueP) monolayer is synthesized via silicon intercalation of the BlueP-Au alloy on Au(111). The intercalation process is characterized at the atomic scale by low-temperature scanning probe microscopy and further corroborated by synchrotron radiation-based X-ray photoelectron spectroscopy measurements. The evolution of the band structures from the BlueP-Au alloy into Si-intercalated BlueP are clearly revealed by angle-resolved photoemission spectroscopy and further verified by density functional theory calculations.

Practical applications of two-dimensional (2D) black phosphorus (BP) are limited by its fast degradation under ambient conditions, for which many different mechanisms have been proposed; however, an atomic level understanding of the degradation process is still hindered by the absence of bottom-up methods for the growth of large-scale few-layer black phosphorus. Recent experimental success in the fabrication of single-layer blue phosphorus provides a model system to probe the oxidation mechanism of two-dimensional (2D) phosphorene down to single-layer thicknesses. Here, we report an atomic-scale investigation of the interaction between molecular oxygen and blue phosphorus. The atomic structure of blue phosphorus and the local binding sites of oxygen have been precisely identified using qPlus-based noncontact atomic force microscopy. A combination of low-temperature scanning tunneling microscopy and X-ray photoelectron spectroscopy measurements reveal a thermally reversible oxidation process of blue phosphorus in a pure oxygen atmosphere. Our study clearly demonstrates the essential role of oxygen in the initial oxidation process, and it sheds further light on the fundamental pathways of the degradation mechanism.

Blue phosphorus, a newly proposed allotrope of phosphorus, represents a promising 2D material with predicted large tunable band gap and high charge-carrier mobility. Here, we report a simple method for the growth of quasi-free-standing single layer blue phosphorus on tellurium functionalized Au(111) by using black phosphorus as the precursor. In situ low-temperature scanning tunneling microscopy (LT-STM) measurements were used to monitor the growth of the single-layer blue phosphorus, which forms triangular structures arranged hexagonally on the tellurium layer. As revealed by in situ X-ray photoelectron spectroscopy, LT-STM measurements, and density functional theory calculation, the blue phosphorus layer weakly interacts with the underlying tellurium layer.

The reversible selective hydrogenation and dehydrogenation of individual manganese phthalocyanine (MnPc) molecules has been investigated using photoelectron spectroscopy (PES), low-temperature scanning tunneling microscopy (LT-STM), synchrotron-based near edge X-ray absorption fine structure (NEXAFS) measurements, and supported by density functional theory (DFT) calculations. It is shown conclusively that interfacial and intramolecular charge transfer arises during the hydrogenation process. The electronic energetics upon hydrogenation is identified, enabling a greater understanding of interfacial and intramolecular charge transportation in the field of single-molecule electronics.