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.

Direct and efficient photocatalytic water splitting is critical for sustainable conversion and storage of renewable solar energy. Here, we propose a conceptual design of two-dimensional CN-based in-plane heterostructure to achieve fast spatial transfer of photoexcited electrons for realizing highly efficient and spontaneous overall water splitting. This unique plane heterostructural carbon ring (C)-CN nanosheet can synchronously expedite electron-hole pair separation and promote photoelectron transport through the local in-plane π-conjugated electric field, synergistically elongating the photocarrier diffusion length and lifetime by 10 times relative to those achieved with pristine g-CN. As a result, the in-plane (C)-CN heterostructure could efficiently split pure water under light irradiation with prominent H production rate up to 371 μmol g h and a notable quantum yield of 5% at 420 nm.

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.

Understanding the kinetics during the metal-insulator transition process is crucial to sort out the underlying physical nature of electron-lattice interactions in correlated materials. Here, based on the temperature-dependent in situ x-ray absorption fine structure measurement and density-functional theory calculations, we have revealed that the monoclinic-to-tetragonal phase transition of VO2 near the critical temperature is characterized by a sharp decrease of the twisting angle δ of the nearest V-V coordination. The VO2 metallization occurs in the intermediate monoclinic like structure with a large twist of V-V pairs when the δ angle is smaller than 1.4°. The correlation between structural kinetics and electronic structure points out that the structural rearrangement is a key factor to narrow the insulating band gap.

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Uncovering the dynamics of active sites in the working conditions is crucial to realizing increased activity, enhanced stability and reduced cost of oxygen evolution reaction (OER) electrocatalysts in proton exchange membrane electrolytes. Herein, we identify at the atomic level potential-driven dynamic-coupling oxygen on atomically dispersed hetero-nitrogen-configured Ir sites (AD-HN-Ir) in the OER working conditions to successfully provide the atomically dispersed Ir electrocatalyst with ultrahigh electrochemical acidic OER activity. Using in-situ synchrotron radiation infrared and X-ray absorption spectroscopies, we directly observe that one oxygen atom is formed at the Ir active site with an O-hetero-Ir-N4 structure as a more electrophilic active centre in the experiment, which effectively promotes the generation of key *OOH intermediates under working potentials; this process is favourable for the dissociation of H2O over Ir active sites and resistance to over-oxidation and dissolution of the active sites. The optimal AD-HN-Ir electrocatalyst delivers a large mass activity of 2860 A gmetal−1 and a large turnover frequency of 5110 h−1 at a low overpotential of 216 mV (10 mA cm−2), 480–510 times larger than those of the commercial IrO2. More importantly, the AD-HN-Ir electrocatalyst shows no evident deactivation after continuous 100 h OER operation in an acidic medium.