Hierarchical MoS2/polyaniline nanowires, integrating MoS2 nanosheets with conductive polyaniline, serve as prominent anode materials for Li‐ion batteries, presenting high capacity and good cyclability. The polyaniline‐hybrid structure and hierarchical features significantly promote the Li‐storage performance as compared with the bare MoS2, indicating new opportunities for developing electrode nanomaterials.

As the key of hydrogen economy, electrocatalytic hydrogen evolution reactions (HERs) depend on the availability of cost-efficient electrocatalysts. Over the past years, there is a rapid rise in noble-metal-free electrocatalysts. Among them, transition metal carbides (TMCs) are highlighted due to their structural and electronic merits, e.g., high conductivity, metallic band states, tunable surface/bulk architectures, etc. Herein, representative efforts and progress made on TMCs are comprehensively reviewed, focusing on the noble-metal-like electronic configuration and the relevant structural/electronic modulation. Briefly, specific nanostructures and carbon-based hybrids are introduced to increase active-site abundance and to promote mass transportation, and heteroatom doping and heterointerface engineering are encouraged to optimize the chemical configurations of active sites toward intrinsically boosted HER kinetics. Finally, a perspective on the future development of TMC electrocatalysts is offered. The overall aim is to shed some light on the exploration of emerging materials in energy chemistry.

MXene-based materials are promising electrode materials for electrochemical capacitors (ECs) due to their unique two-dimensional layered structure, high surface area, remarkable chemical stability, and electrical conductivity. TiO2 nanoparticles decorated Ti3C2 MXene were synthesized through a simple in situ hydrolysis and heat-treatment process and subsequently fabricated as an electrode for ECs. The as-prepared Ti3C2, TiO2, and TiO2-Ti3C2 were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The results indicated that TiO2 nanoparticles with a diameter of less than 30 nm were decorated onto the Ti3C2 MXene nanosheets. The resulting composites exhibited significantly higher specific capacitance of 143 F g−1 at 5 mV s−1, which was 1.5 times that of pure Ti3C2 (93 F g−1). Moreover, TiO2-Ti3C2 showed excellent cycling stability, retaining ∼92% of its initial capacitance after 6000 cycles. These results suggest that TiO2-Ti3C2 nanocomposite has the potential as an electrode material for high-performance energy storage devices.

A facile and controllable strategy, which combines solvothermal treatment with ex situ nitrogen doping by using urea saturated alcohol solution or monoethanolamine as nitrogen source, is used to prepare flexible, freestanding, and compact nitrogen‐doped delaminated Ti3C2 (abbreviated N‐Ti3C2) film electrodes for symmetric electrochemical capacitors (ECs). Compared with the N sites from in situ N solid solution doping, those of ex situ N solvothermal doping enable larger contributions to the capacitance through regulating nitrogen species and content. As a result, the urea‐assisted N‐Ti3C2 (UN‐Ti3C2) film exhibits an ultrahigh volumetric capacitance of 2836 F cm−3 (927 F g−1) at 5 mV s−1 in 3 m H2SO4 solution. This value surpasses the all previously reported volumetric performance of MXenes. A large capacitance of 2643 F cm−3 (786 F g−1) is also obtained for the monoethanolamine‐assisted N‐Ti3C2 film. In addition, the symmetric electrochemical capacitor fabricated from the binder‐free UN‐Ti3C2 film exhibits a high volumetric energy density of 76 Wh L−1, which is the highest value achieved compared to those of MXenes so far. This work presents the effects of nitrogen species and solvothermal treatment on the electrochemical performance of MXene, and opens up an exciting opportunity for fabricating highly flexible and integrated ECs.