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Developing highly efficient transition metal dichalcogenide electrocatalysts would be significantly beneficial for the electrocatalytic hydrogen evolution reaction (HER) from water splitting. Herein, we reported novel ultrathin tantalum disulfide nanosheets (TaS2NSs) prepared by electrochemically exfoliating bulk TaS2with an alternating voltage in an acidic electrolyte. The obtained TaS2NS electrocatalyst possessed an ultrathin structure with a lateral size of 2 μm and a thickness of ∼3 nm. Owing to the unique 2D structure, the achieved TaS2NSs displayed remarkable electrocatalytic activity toward the HER by a small overpotential of 197 mV at 10 mA cm–2and a small Tafel slope of 100 mV dec–1in acidic solution, much lower than those of TaS2(>547 mV and 216 mV dec–1, respectively) and other reported TaS2-based HER electrocatalysts. Furthermore, highly efficient full water splitting could be realized with two electrodes in which TaS2NSs acted as the cathode while Ir/C served as the anode, with help of two AA size batteries or solar cells. By replacing the oxygen evolution reaction with the urea oxidation reaction (UOR), bifunctional TaS2NSs enabled an energy-effective HER process in the cathode and UOR process in the anode with decreased applied potential.

Two-dimensional (2D) niobium disulfide (NbS2) materials feature unique physical and chemical properties leading to highly promising energy conversion applications. Herein, we developed a robust synthesis technique consisting of electrochemical exfoliation under alternating currents and subsequent liquid-phase exfoliation to prepare highly uniform few-layer NbS2nanosheets. The obtained few-layer NbS2material has a 2D nanosheet structure with an ultrathin thickness of ∼3 nm and a lateral size of ∼2 μm. Benefiting from their unique 2D structure and highly exposed active sites, the few-layer NbS2nanosheets drop-casted on carbon paper exhibited excellent catalytic activity for the hydrogen evolution reaction (HER) in acid with an overpotential of 90 mV at a current density of 10 mA cm–2and a low Tafel slope of 83 mV dec–1, which are superior to those reported for other NbS2-based HER electrocatalysts. Furthermore, few-layer NbS2nanosheets are effective as bifunctional electrocatalysts for hydrogen production by overall water splitting, where the urea and hydrazine oxidation reactions replace the oxygen evolution reaction.

Thanks to tunable physical and chemical properties, two-dimensional (2D) materials have received intensive interest, endowing their excellent electrocatalytic performances for applications in energy conversion. However, their catalytic activities are largely determined by poor adsorption energy and limited active edge sites. Herein, a one-step electrochemical exfoliation strategy was developed to fabricate 2D Ni-doped MoS2nanosheets (Ni-EX-MoS2) with a lateral size of ∼500 nm and thickness of ∼3.5 nm. Profiting from high electrical conductivity and abundant exposing active sites, Ni-EX-MoS2catalyst displayed an admirable performance for electrochemical hydrogen evolution reaction (HER) with a low overpotential of 145 mV at 10 mA/cm2as well as a small Tafel slope of 89 mV/dec in alkaline media, which are superior to those of the most reported MoS2-based electrocatalysts. The formed Ni species with tuning electronic structure played a crucial role as primary active center of Ni-EX-MoS2, as well as the forming stable 1T/2H phase MoS2interface demonstrated a synergistic effect on electrocatalytic HER performance. Further, Ni-EX-MoS2was employed as a cathode electrode for alkaline Zn-H2O battery, which displayed a high power density of 3.3 mW/cm2with excellent stability. This work will provide a simple and effective guideline for design of electrochemically exfoliated transition metal-doped MoS2nanosheets to inspire their practical applications in energy catalytic and storage.

Herein, we demonstrate the successful utilization of reticular chemistry as an excellent designing strategy for the deliberate construction of a zirconium–tetracarboxylate metal–organic framework (MOF) inspired by the Olympic rings. HIAM-4017, with an unprecedented (4,8)-c underlying net topology termed jcs, was developed via insightful reconstruction of the rings and judicious design of a nonsymmetric organic linker. HIAM-4017 exhibits high porosity and excellent chemical and thermal stability. Furthermore, excited-state intramolecular proton transfer (ESIPT) was achieved in an isoreticular MOF, HIAM-4018, with a large Stokes shift of 155 nm as a result of introducing the hydroxyl group to the linker skeleton to induce OH···N interactions. Such interactions were analyzed thoroughly by employing the time-dependent density functional theory (TD-DFT). Because of their good thermal and chemical stability, and strong luminescence, nanosized HIAM-4017 and HIAM-4018 were fabricated and used for Cr2O72–detection. Both MOFs demonstrate excellent sensitivity and selectivity. This work represents a neat example of building structure- and property-specific MOFs guided by reticular chemistry.