Outstanding magnetic properties are highly desired for two-dimensional ultrathin semiconductor nanosheets. Here, we propose a phase incorporation strategy to induce robust room-temperature ferromagnetism in a nonmagnetic MoS2 semiconductor. A two-step hydrothermal method was used to intentionally introduce sulfur vacancies in a 2H-MoS2 ultrathin nanosheet host, which prompts the transformation of the surrounding 2H-MoS2 local lattice into a trigonal (1T-MoS2) phase. 25% 1T-MoS2 phase incorporation in 2H-MoS2 nanosheets can enhance the electron carrier concentration by an order, introduce a Mo(4+) 4d energy state within the bandgap, and create a robust intrinsic ferromagnetic response of 0.25 μB/Mo by the exchange interactions between sulfur vacancy and the Mo(4+) 4d bandgap state at room temperature. This design opens up new possibility for effective manipulation of exchange interactions in two-dimensional nanostructures.

Endowing transition-metal oxide electrocatalysts with high water oxidation activity is greatly desired for production of clean and sustainable chemical fuels. Here, we present an atomically thin cobalt oxyhydroxide (γ-CoOOH) nanosheet as an efficient electrocatalyst for water oxidation. The 1.4 nm thick γ-CoOOH nanosheet electrocatalyst can effectively oxidize water with extraordinarily large mass activities of 66.6 A g(-1), 20 times higher than that of γ-CoOOH bulk and 2.4 times higher than that of the benchmarking IrO2 electrocatalyst. Experimental characterizations and first-principles calculations provide solid evidence to the half-metallic nature of the as-prepared nanosheets with local structure distortion of the surface CoO(6-x) octahedron. This greatly enhances the electrophilicity of H2O and facilitates the interfacial electron transfer between Co ions and adsorbed -OOH species to form O2, resulting in the high electrocatalytic activity of layered CoOOH for water oxidation.

Finding ideal material models for studying the role of catalytic active sites remains a great challenge. Here we propose pits confined in an atomically thin sheet as a platform to evaluate carbon monoxide catalytic oxidation at various sites. The artificial three-atomic-layer thin cerium(IV) oxide sheet with approximately 20% pits occupancy possesses abundant pit-surrounding cerium sites having average coordination numbers of 4.6 as revealed by X-ray absorption spectroscopy. Density-functional calculations disclose that the four-and five-fold coordinated pit-surrounding cerium sites assume their respective role in carbon monoxide adsorption and oxygen activation, which lowers the activation barrier and avoids catalytic poisoning. Moreover, the presence of coordination-unsaturated cerium sites increases the carrier density and facilitates carbon monoxide diffusion along the two-dimensional conducting channels of surface pits. The atomically thin sheet with surface-confined pits exhibits lower apparent activation energy than the bulk material (61.7 versus 122.9 kJ mol À 1 ), leading to reduced conversion temperature and enhanced carbon monoxide catalytic ability.

Lead halide perovskite (PVK) has been deemed as a promising photocatalyst alternative because of its remarkable photoelectrical properties; however, the severe charge recombination has limited its catalytic activity. Herein, we report a PVK-based Z-scheme heterojunction, a-Fe 2 O 3 /Amine-RGO/CsPbBr 3 , for highefficiency CO 2 reduction in the presence of H 2 O. By delicately controlling the interfacial interaction, effective Z-scheme electron transfer from a-Fe 2 O 3 to CsPbBr 3 is built, leading to boosted charge separation and prolonged carrier lifetime, as confirmed by electron spin resonance (ESR), transient absorption (TA) spectra, etc. The impactful spatial separation of photo-generated carriers in Z-scheme system finally enables an 8.3-fold enhancement in photocatalytic performance as compared to CsPbBr 3 . A stable product yield of 469.16 mmol g À1 and an electron consumption yield of 3,132.46 mmol g À1 are achieved. This work is expected to provide deep insights into boosting the photocatalytic performance of PVK by modulating the charge carrier dynamics.

Heterojunction engineering has played an indispensable role in the exploitation of innovative artificial materials with exceptional properties and has consequently triggered a new revolution in achieving high-performance optoelectronic devices. Herein, an intriguing halide perovskite (PVK) and metal dichalcogenide (MD) heterojunction, i.e., a lead-free Cs2SnI6 perovskite nanocrystal/SnS2 nanosheet hybrid, was fabricated in situ for the first time. Comprehensive investigations with experimental characterizations and theoretical calculations demonstrate that cosharing of the Sn atom enables intimate contact in the Cs2SnI6/SnS2 hybrid together with a type II band alignment structure. Additionally, ultrafast carrier separation between SnS2 and Cs2SnI6 has been observed in the Cs2SnI6/SnS2 hybrid by transient absorption measurements, which efficiently prolongs the lifetime of the photogenerated electrons in SnS2 (from 1290 to 3080 ps). The resultant spatial charge separation in the Cs2SnI6/SnS2 hybrid evidenced by Kelvin probe force microscopy (KPFM) significantly boosts the photocatalytic activity toward CO2 reduction and the photoelectrochemical performance, with 5.4-fold and 10.6-fold enhancements compared with unadorned SnS2. This work provides a facile and effective method for the in situ preparation of PVK-MD heterojunctions, which may significantly stimulate the synthesis of various perovskite-based hybrid materials and their further optoelectronic applications.

A luminescent all-inorganic manganese-bismuth heterometallic Cs 4 MnBi 2 Cl 12 perovskite single crystal has been synthesized with a [BiCl 6 ] 3À -[MnCl 6 ] 4À -[BiCl 6 ] 3À triple-layered two-dimensional structure. Benefit from the effective energy transfer from [BiCl 6 ] 3À octahedron donor to luminescent [MnCl 6 ] 4À acceptor, Cs 4 MnBi 2 Cl 12 shows a photoluminescence quantum yield (PLQY) of up to 25.7% (~610 nm), 51-fold higher than the Bi unalloyed CsMnCl 3 $2H 2 O counterpart. Suggested by the theoretical calculations, Bi and Mn exhibit hybridization in conduction and valence band, which further results in a favorable low activation energy for exciton transfer (~23 meV). By virtue of all-inorganic chemical composition, Cs 4 MnBi 2 Cl 12 exhibits impressive stability toward moisture, light, and heat. Furthermore, Cs 4 MnBi 2 Cl 12 features strong soft X-ray attenuation and bright radiative luminescence under X-ray excitation, which pave a way for its application in medical flat-panel X-ray digital radiography. This work presents a new avenue toward fabrication of function-directed material with tailored photoelectric properties.

Understanding the initial nucleation mechanism of monodisperse nanocrystals (NCs) during synthesis process is an important prerequisite to control the desired sizes and to manipulate the properties of nanoscale materials. The acquisition of information for the small nanocluster nucleation process, however, still remains challenging. Here, using a continuous-flow in situ X-ray absorption fine structure (XAFS) spectroscopy for time-resolved studies, we have clarified the initial kinetic nucleation of Au clusters under the grain size of 1 nm for the classical Au NCs synthesis via the reduction of AuCl(4)(-) in aqueous solution. The in situ XAFS results present the experimental revelation of the formation of intermediate Cl(3)(-)Au-AuCl(3)(-) dimer and the subsequent higher complexes 'Au(n)Cl(n+x)' in the initial nucleation stage. We propose a kinetic three-step mechanism involving the initial nucleation, slow growth, and eventual coalescence for the Au NCs formation, which may be helpful for the synthesis of metallic nanomaterials.

There remains a pressing challenge in the efficient utilization of visible light in the photoelectrochemical applications of water splitting. Here, we design and fabricate pseudobrookite Fe 2 TiO 5 ultrathin layers grown on vertically aligned TiO 2 nanotube arrays that can enhance the conduction and utilization of photogenerated charge carriers. Our photoanodes are characterized by low onset potentials of B0.2 V, high photon-to-current efficiencies of 40-50% under 400-600 nm irradiation and total energy conversion efficiencies of B2.7%. The high performance of Fe 2 TiO 5 nanotube arrays can be attributed to the anisotropic charge carrier transportation and elongated charge carrier diffusion length (compared with those of conventional TiO 2 or Fe 2 O 3 photoanodes) based on electrochemical impedance analysis and first-principles calculations. The Fe 2 TiO 5 nanotube arrays may open up more opportunities in the design of efficient and low-cost photoanodes working in visible light for photoelectrochemical applications.