Cheng Yan

Intensive research into atomically thin two-dimensional (2D) transition metal dichalcogenides (TMDs) has revealed remarkable physicochemical properties, positioning them as promising candidates for advanced functional electronic and optoelectronic devices beyond conventional silicon-based technologies. Beyond pristine monolayer TMDs with diverse elemental compositions, the development of compositionally tunable alloys, heterostructures, and superlattices composed of distinct TMDs has enabled the exploration of emergent physical phenomena and functionalities. However, the controllable synthesis of large-area, high-quality 2D TMDs with well-defined compositions and architectures remains a fundamental prerequisite for both basic research and practical applications. While mechanical exfoliation has been extensively adopted for constructing TMDs-based heterostructures and superlattices, it lacks scalability and structural precision. In contrast, chemical vapor deposition (CVD) has emerged as a versatile and scalable approach for synthesizing a broad spectrum of TMDs including monolayers, alloys, vertical/lateral heterostructures, and superlattices. This review provides a comprehensive and critical overview of recent progress in the CVD synthesis of 2D TMDs. Particular attention is given to nucleation and growth mechanisms, and the structural and functional diversity achieved through alloying and hetero-integration. Finally, we outline key challenges and promising directions for future research in this rapidly evolving field.

Developing efficient and cost-effective electrode materials is of essential significance to advance various energy storage technologies, among which flexible supercapacitors hold great promise to meet the growing popularity of wearable electronics. Herein, we report a homologous strategy to parallelly synthesize phosphorus-doped ZnCo₂O₄ (P-ZnCo₂O₄@NCC) and nitrogen-doped carbon (NC@NCC) both derived from ZnCo-metal-organic frameworks (MOFs) precursors in-situ grown on dopamine-modified carbon cloth (NCC) as conductive substrates. Impressively, the as-obtained P-ZnCo₂O₄@NCC can achieve a high specific capacitance of 2702.2 mF·cm⁻² at 1 mA·cm⁻² with the capacitance retention rate exceeding 70.6% at 10 mA·cm⁻², demonstrating the outstanding rate capability. Moreover, flexible solid-state hybrid supercapacitors, using P-ZnCo₂O₄@NCC as positive electrode and NC@NCC as negative electrode, are assembled with poly(vinyl alcohol) (PVA)/KOH as the gel electrolyte, which deliver the energy density of 11.9 mWh·cm⁻³ when the power density reaches up to 47.3 mW·cm⁻³. In addition, 85.15% of the initial specific capacitance is maintained after 5000 continuous cycles and no obvious capacitance decay is observed under different bending conditions, revealing the excellent cycling stability and flexibility. As a proof-of-concept demonstration, two as-assembled hybrid supercapacitors connected in series can light up a red light-emitting diode (LED) under the bending angle of 180°, heralding the feasibility for broad practical applications.

Efficient bifunctional electrocatalysts for hydrogen and oxygen evolution reactions are key to water electrolysis. Herein, we report a built‐in electric field (BEF) strategy to fabricate heterogeneous nickel phosphide‐cobalt nanowire arrays grown on carbon fiber paper (Ni₂P‐CoCH/CFP) with large work function difference (ΔΦ) as bifunctional electrocatalysts for overall water splitting. Impressively, Ni₂P‐CoCH/CFP exhibits a remarkable catalytic activity for hydrogen and oxygen evolution reactions to obtain 10 mA cm⁻², respectively. Moreover, the assembled lab‐scale electrolyzer driven by an AAA battery delivers excellent stability after 50 h electrocatalysis with a 100 % faradic efficiency. Computational calculations combining with experiments reveal the interface‐induced electric field effect facilitates asymmetrical charge distributions, thereby regulating the adsorption/desorption of the intermediates during reactions. This work offers an avenue to rationally design high‐performance heterogeneous electrocatalysts.

Efficient bifunctional electrocatalysts for hydrogen and oxygen evolution reactions are key to water electrolysis. Herein, we report a built‐in electric field (BEF) strategy to fabricate heterogeneous nickel phosphide‐cobalt nanowire arrays grown on carbon fiber paper (Ni₂P‐CoCH/CFP) with large work function difference (ΔΦ) as bifunctional electrocatalysts for overall water splitting. Impressively, Ni₂P‐CoCH/CFP exhibits a remarkable catalytic activity for hydrogen and oxygen evolution reactions to obtain 10 mA cm⁻², respectively. Moreover, the assembled lab‐scale electrolyzer driven by an AAA battery delivers excellent stability after 50 h electrocatalysis with a 100 % faradic efficiency. Computational calculations combining with experiments reveal the interface‐induced electric field effect facilitates asymmetrical charge distributions, thereby regulating the adsorption/desorption of the intermediates during reactions. This work offers an avenue to rationally design high‐performance heterogeneous electrocatalysts.

Single‐atom catalysts (SACs) attract intensive attention owing to their unmatched catalytic activities and high atom utilization. Besides metal species themselves, the substrates play a key role for the improvement of their catalytic performance by optimizing metal–support interactions and coordination structures. In the past years, various 2D nanomaterials have been employed to anchor single metal atoms for renewable energy technologies and other important industrial processes. Tremendous progress has been achieved in the development of 2D supported SACs for advanced energy conversion reactions. This article provides a comprehensive and critical review of up‐to‐date advances in the field of 2D supported SACs. The state‐of‐the‐art characterizations including ex/in situ microscopic and spectroscopic techniques are summarized with the emphasis on their specific superiorities in identifying the reactive sites and reaction mechanisms, combined with theoretical calculations and experimental results. A brief overview of various reactions including hydrogen evolution reaction (HER), oxygen evolution reaction (OER), two‐electron oxygen reduction reaction (2e‐ORR), carbon dioxide reduction (CO₂RR), and nitrogen reduction reaction (NRR) under the framework of electrocatalysis and photocatalysis, is presented on basis of versatile 2D nanomaterial supports. Last, the key challenges and opportunities in this rising field are highlighted.

Nitrogen-doped SnO₂ nanorods were synthesized via facile solvothermal processes, which demonstrated enhanced photocatalytic performances evaluated by the degradation of rhodamine B (RhB), revealing the effectiveness of nitrogen doping towards photocatalysis.

Rational materials design for the synthesis of desirable hollow micro- and nanostructures has recently revealed the remarkable potential for high-performance energy storage and conversion devices. Owing to their unique “core–void–shell” structural configurations, yolk–shell-structured electrode materials can achieve intimate contact with the electrolyte and alleviate the volume expansion issue during electrochemical cycling, which is therefore poised to further boost the electrochemical properties of hybrid supercapacitors. Herein, a facile self-templated strategy, consisting of a hydrothermal step and a high-temperature sulfurization process, has been developed for the construction of yolk–shell (NiCo)₉S₈ spheres in situ coated by graphite carbon ((NiCo)₉S₈/GC) due to the non-equilibrium thermal treatment of alkali metal alkoxides. The as-synthesized yolk–shelled sphere exhibits a high specific capacitance of 1434.4 F g⁻¹ (179.3 mA h g⁻¹) at a current density of 1 A g⁻¹, and good rate capability and cycling stability with 83.1% capacitance retention at 8 A g⁻¹ over 5000 cycles. To further demonstrate its practical application, a hybrid supercapacitor device was assembled using (NiCo)₉S₈/GC as the battery-type positive electrode and activated carbon (AC) as the capacitive-type electrode. The as-fabricated device can reach a wide voltage window of up to 1.6 V, deliver a high energy density of 55.6 W h kg⁻¹ at a power density of 800.3 W kg⁻¹ and maintain 90.2% of specific capacitance after 3000 cycles.