Rhodium and Carbon Sites with Strong d-p Orbital Interaction for Efficient Bifunctional Catalysis.

Efficient and stable catalysts are highly desired for the electrochemical conversion of hydrogen, oxygen, and water molecules, processes which are crucial for renewable energy conversion and storage technologies. Herein, we report the development of hollow nitrogenated carbon sphere (HNC) dispersed rhodium (Rh) single atoms (RhHNC) as an efficient catalyst for bifunctional catalysis. The RhHNC was achieved by anchoring Rh single atoms in the HNC matrix with an Rh-NC configuration, via a combination of polymerization and carbonization approach.

Construction of Co Atomic Clusters to Enable Fe-N Motifs with Highly Active and Durable Oxygen Reduction Performance.

Fe-N-C catalysts with single-atom Fe-N configurations are highly needed owing to the high activity for oxygen reduction reaction (ORR). However, the limited intrinsic activity and dissatisfactory durability have significantly restrained the practical application of proton-exchange membrane fuel cells (PEMFCs). Here, we demonstrate that constructing adjacent metal atomic clusters (ACs) is effective in boosting the ORR performance and stability of Fe-N catalysts.

Carbon Nitride Photocatalysts with Integrated Oxidation and Reduction Atomic Active Centers for Improved CO Conversion.

Single-atom active-site catalysts have attracted significant attention in the field of photocatalytic CO conversion. However, designing active sites for CO reduction and H O oxidation simultaneously on a photocatalyst and combining the corresponding half-reaction in a photocatalytic system is still difficult. Here, we synthesized a bimetallic single-atom active-site photocatalyst with two compatible active centers of Mn and Co on carbon nitride (Mn Co /CN).

An Adjacent Atomic Platinum Site Enables Single-Atom Iron with High Oxygen Reduction Reaction Performance.

The modulation effect has been widely investigated to tune the electronic state of single-atomic M-N-C catalysts to enhance the activity of oxygen reduction reaction (ORR). However, the in-depth study of modulation effect is rarely reported for the isolated dual-atomic metal sites. Now, the catalytic activities of Fe-N moiety can be enhanced by the adjacent Pt-N moiety through the modulation effect, in which the Pt-N acts as the modulator to tune the 3d electronic orbitals of Fe-N active site and optimize ORR activity.

One-step synthesis of single-site vanadium substitution in 1T-WS monolayers for enhanced hydrogen evolution catalysis.

Metallic tungsten disulfide (WS) monolayers have been demonstrated as promising electrocatalysts for hydrogen evolution reaction (HER) induced by the high intrinsic conductivity, however, the key challenges to maximize the catalytic activity are achieving the metallic WS with high concentration and increasing the density of the active sites. In this work, single-atom-V catalysts (V SACs) substitutions in 1T-WS monolayers (91% phase purity) are fabricated to significantly enhance the HER performance via a one-step chemical vapor deposition strategy. Atomic-resolution scanning transmission electron microscopy (STEM) imaging together with Raman spectroscopy confirm the atomic dispersion of V species on the 1T-WS monolayers instead of energetically favorable 2H-WS monolayers.

Carbon-Supported Single-Atom Catalysts for Formic Acid Oxidation and Oxygen Reduction Reactions.

The commercialization of fuel cells, especially for direct formic acid fuel cells (DFAFCs) and proton-exchange membrane fuel cells (PEMFCs), is significantly restrained by the high cost, poor stability, and sluggish kinetics of platinum group metals (PGM) catalysts for both the anodic formic acid oxidation reaction (FAOR) and the cathodic oxygen reduction reaction (ORR). Currently, it has confronted with challenges, including exploring highly active, cost-effective, and stable catalysts to replace PGM for DFAFCs and PEMFCs. Recently, the increasing investigation has been focused on the single-atom catalysts (SACs) to enhance the catalytic performance owing to the maximum atom utilization and highly exposed active sites.

Mobility-Fluctuation-Controlled Linear Positive Magnetoresistance in 2D Semiconductor BiOSe Nanoplates.

Linear magnetoresistance is generally observed in polycrystalline zero-gap semimetals and polycrystalline Dirac semimetals with ultrahigh carrier mobility. We report the observation of positive and linear magnetoresistance in a single-crystalline semiconductor BiOSe grown by chemical vapor deposition. Both Se-poor and Se-rich BiOSe single-crystalline nanoplates display a linear magnetoresistance at high fields.

Unveiling defect-mediated carrier dynamics in monolayer semiconductors by spatiotemporal microwave imaging.

The optoelectronic properties of atomically thin transition-metal dichalcogenides are strongly correlated with the presence of defects in the materials, which are not necessarily detrimental for certain applications. For instance, defects can lead to an enhanced photoconduction, a complicated process involving charge generation and recombination in the time domain and carrier transport in the spatial domain. Here, we report the simultaneous spatial and temporal photoconductivity imaging in two types of WS monolayers by laser-illuminated microwave impedance microscopy.

Solution-Processed Mixed-Dimensional Hybrid Perovskite/Carbon Nanotube Electronics.

Benefiting from their extraordinary physical properties, methylammonium lead halide perovskites (PVKs) have attracted significant attention in optoelectronics. However, the PVK-based devices suffer from low carrier mobility and high operation voltage. Here, we utilize sorted semiconducting single-walled carbon nanotubes (95% s-SWCNTs) to enhance the performance of thin-film transistors (TFTs) based on the mixed-cation perovskite (MAFA)Pb(IBr), enabling mixed-dimensional solution-processed electronics with high mobility (32.

Quasi-Two-Dimensional Se-Terminated Bismuth Oxychalcogenide (BiOSe).

Since the discovery of graphene, van der Waals (vdW) two-dimensional (2D) materials have attracted considerable attention for various potential applications. Recently, a Se-terminated bismuth oxychalcogenide, BiOSe, has been fabricated using the vapor deposition method. BiOSe is not a vdW 2D material, but the as-grown substance shows 2D characteristics.

Gate-Tunable and Multidirection-Switchable Memristive Phenomena in a Van Der Waals Ferroelectric.

Memristive devices have been extensively demonstrated for applications in nonvolatile memory, computer logic, and biological synapses. Precise control of the conducting paths associated with the resistance switching in memristive devices is critical for optimizing their performances including ON/OFF ratios. Here, gate tunability and multidirectional switching can be implemented in memristors for modulating the conducting paths using hexagonal α-In Se , a semiconducting van der Waals ferroelectric material.

Energy-Resolved Photoconductivity Mapping in a Monolayer-Bilayer WSe Lateral Heterostructure.

Vertical and lateral heterostructures of van der Waals materials provide tremendous flexibility for band-structure engineering. Because electronic bands are sensitively affected by defects, strain, and interlayer coupling, the edge and heterojunction of these two-dimensional (2D) systems may exhibit novel physical properties, which can be fully revealed only by spatially resolved probes. Here, we report the spatial mapping of photoconductivity in a monolayer-bilayer WSe lateral heterostructure under multiple excitation lasers.

Multidirection Piezoelectricity in Mono- and Multilayered Hexagonal α-InSe.

Piezoelectric materials have been widely used for sensors, actuators, electronics, and energy conversion. Two-dimensional (2D) ultrathin semiconductors, such as monolayer h-BN and MoS with their atom-level geometry, are currently emerging as new and attractive members of the piezoelectric family. However, their piezoelectric polarization is commonly limited to the in-plane direction of odd-number ultrathin layers, largely restricting their application in integrated nanoelectromechanical systems.

Crystalline Copper Phosphide Nanosheets as an Efficient Janus Catalyst for Overall Water Splitting.

Hydrogen is essential to many industrial processes and could play an important role as an ideal clean energy carrier for future energy supply. Herein, we report for the first time the growth of crystalline CuP phosphide nanosheets on conductive nickel foam (CuP@NF) for electrocatalytic and visible light-driven overall water splitting. Our results show that the CuP@NF electrode can be used as an efficient Janus catalyst for both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER).

Oxyanion induced variations in domain structure for amorphous cobalt oxide oxygen evolving catalysts, resolved by X-ray pair distribution function analysis.

Amorphous thin film oxygen evolving catalysts, OECs, of first-row transition metals show promise to serve as self-assembling photoanode materials in solar-driven, photoelectrochemical `artificial leaf' devices. This report demonstrates the ability to use high-energy X-ray scattering and atomic pair distribution function analysis, PDF, to resolve structure in amorphous metal oxide catalyst films. The analysis is applied here to resolve domain structure differences induced by oxyanion substitution during the electrochemical assembly of amorphous cobalt oxide catalyst films, Co-OEC.

Synthesis and enhanced electrochemical catalytic performance of monolayer WS2(1-x) Se2x with a tunable band gap.

The first realization of a tunable band-gap in monolayer WS2(1-x) Se2x is demonstrated. The tuning of the bandgap exhibits a strong dependence of S and Se content, as proven by PL spectroscopy. Because of its remarkable electronic structure, monolayer WS2(1-x) Se2x exhibits novel electrochemical catalytic activity and offers long-term electrocatalytic stability for the hydrogen evolution reaction.

High catalytic activity for water oxidation based on nanostructured nickel phosphide precursors.

For the first time, noble-metal-free nickel phosphide (Ni2P) was used as an excellent catalyst precursor for water oxidation catalysis. The lowest onset potential was observed at ∼1.54 V (vs.

Atomic scale analysis of the enhanced electro- and photo-catalytic activity in high-index faceted porous NiO nanowires.

Catalysts play a significant role in clean renewable hydrogen fuel generation through water splitting reaction as the surface of most semiconductors proper for water splitting has poor performance for hydrogen gas evolution. The catalytic performance strongly depends on the atomic arrangement at the surface, which necessitates the correlation of the surface structure to the catalytic activity in well-controlled catalyst surfaces. Herein, we report a novel catalytic performance of simple-synthesized porous NiO nanowires (NWs) as catalyst/co-catalyst for the hydrogen evolution reaction (HER).

Green cobalt oxide (CoOx) film with nanoribbon structures electrodeposited from the BF₂-annulated cobaloxime precursor for efficient water oxidation.

In this study, we report for the first time on the use of a water-soluble BF2-annulated cobaloxime, Co(dmgBF2)2(OH2)2 (Co-DMB, dmgBF2 = difluoroboryl-dimethylglyoxime), as a catalyst precursor for electrocatalytic water oxidation. Oxygen gas bubbles were clearly produced on the FTO electrode at a low overpotential under neutral pH conditions containing Co-DMB. Interestingly, stable green films were produced under these conditions.

Cobalt porphyrin electrode films for electrocatalytic water oxidation.

Catalysts play very important roles in artificial photosynthesis for solar energy conversion. In this present study, two water-insoluble cobalt porphyrin complexes, cobalt(II) meso-tetraphenylporphyrin (CoP-1) and cobalt(II) 5,10,15,20-tetrakis-(4-bromophenyl)porphyrin (CoP-2), were synthesized and coated as thin films on the FTO working electrode. The films showed good activities for electrocatalytic water oxidation in aqueous solutions at pH 9.

Reversible mechanochromic luminescence at room temperature in cationic platinum(II) terpyridyl complexes.

Reversible mechanochromic luminescence in cationic platinum(II) terpyridyl complexes is described. The complexes [Pt(Nttpy)Cl]X2 (Nttpy = 4'-(p-nicotinamide-N-methylphenyl)-2,2':6',2″-terpyridine, X = PF6 (1), SbF6 (2), Cl (3), ClO4 (4), OTf (5), BF4 (6)) exhibit different colors under ambient light in the solid state, going from red to orange to yellow. All of these complexes are brightly luminescent at both room temperature and 77 K.

Electrochemical, spectroscopic and theoretical studies of a simple bifunctional cobalt corrole catalyst for oxygen evolution and hydrogen production.

Six cobalt and manganese corrole complexes were synthesized and examined as single-site catalysts for water splitting. The simple cobalt corrole [Co(tpfc)(py)2] (1, tpfc = 5,10,15-tris(pentafluorophenyl)corrole, py = pyridine) catalyzed both water oxidation and proton reduction efficiently. By coating complex 1 onto indium tin oxide (ITO) electrodes, the turnover frequency for electrocatalytic water oxidation was 0.

Facile deposition of nanostructured cobalt oxide catalysts from molecular cobaloximes for efficient water oxidation.

Cobaloximes are usually used as molecular hydrogen evolution reaction (HER) catalysts. Herein we report for the first time the use of molecular cobaloximes as catalyst precursors for water oxidation when anodic potentials were applied. Highly active thin catalyst films were deposited at +1.