二维共轭碳材料/TiO2复合光催化剂制备及表征

选用两种二维共轭碳材料石墨烯(GR)和石墨炔(GD),通过水热合成的方法原位生长制备TiO_2-GR和尿素分散的TiO_2-GR以及TiO_2-GD复合材料光催化剂,对3种复合材料催化剂的表面形貌和物相结构进行表征,并测试3种催化剂光催化剂性能。结果表明,石墨烯和石墨炔的加入,对TiO_2起到明显的分散作用,TiO_2颗粒与石墨烯和石墨炔紧密结合;尿素的加入使TiO_2-GR颗粒尺寸进一步减小,TiO_2分散度进一步提高。在模拟太阳光辐射下,一定时间内光催化剂光降解有机染料亚甲基蓝和甲基橙,结果表明,二维共轭碳材料石墨烯和石墨炔的加入使复合材料光催化剂TiO_2-GR和TiO_2-GD的光催化性能为纯TiO_2光催化剂的1. 67倍和1. 68倍,复合材料光催化剂表现出更优秀的催化性能。     

Synthesis and Self-Assembly of Ultrathin Holey Graphdiyne Nanosheets for Oxygen Reduction Reaction

Graphdiyne (GDY) is a fascinating graphene-like 2D carbon allotrope comprising sp and sp² hybridized carbon atoms. However, GDY materials synthesized by solution-phase methods normally come as thick and porous films or amorphous powders with severely disordered stacking modes that obstruct macroscopic applications. Here, a facile and scalable synthesis of ultrathin holey graphdiyne (HGDY) nanosheets is reported via palladium/copper co-catalyzed homocoupling of 1,3,5-triethynylbenzene. The resulting freestanding 2D HGDY self-assembles into 3D foam-like networks which can in situ anchor clusters of palladium atoms on their surfaces. The Pd/HGDY hybrids exhibit high electrocatalytic activity and stability for the oxygen reduction reaction which outperforms that of Pt/C benchmark. Based on the ultrathin graphene-like sheets and their unique 3D interconnected macrostructures, Pd/HGDY holds great promise for practical electrochemical catalysis and energy-related applications.     

Superhydrophilic Graphdiyne Accelerates Interfacial Mass/Electron Transportation to Boost Electrocatalytic and Photoelectrocatalytic Water Oxidation Activity

Graphdiyne (GDY), with a highly π‐conjugated structure of sp²‐ and sp‐hybridized carbon, has triggered a huge interest in water splitting. However, all of the systems perform with no consideration of the surface wettability of GDY. Herein, for the first time, the fabrication of superhydrophilic GDY electrode via air‐plasma for oxygen evolution is described. As a representative catalyst, ultrathin CoAl‐LDH (CO₃^2?) nanosheets have been successfully assembled onto the superhydrophilic GDY electrostatically. The resulting superhydrophilic CoAl‐LDH/GDY electrode exhibites superior activity with an overpotential of ≈258 mV to reach 10 mA cm^?2. The turnover frequency (TOF) is calculated to be ≈0.60 s^?1 at η = 300 mV, which is the best record in both CoAl‐based and GDY‐based layered double hydroxides (LDH) electrocatalysts for oxygen evolution. Density functional theory (DFT) calculations reveal that superhydrophilic GDY has stronger interactions with catalysts and attracts H₂O molecules around catalysts, thus facilitating interfacial mass/electron transportation. Further, the fabrication is capable of improving the photoelectrochemical oxygen evolution activity remarkably. The results show the great potential of superhydrophilic GDY to boost water oxidation activity by promoting interfacial mass/electron transportation.     

Graphdiyne: A New Photocatalytic CO2 Reduction Cocatalyst

Exploring new and efficient cocatalysts to boost photocatalytic CO₂ reduction is of critical importance for solar‐to‐fuel conversion. As an emerging carbon allotrope, graphdiyne (GDY) features 2D characteristics and unique carbon–carbon bonds. Herein, a novel GDY cocatalyst coupled TiO₂ nanofibers for boosted photocatalytic CO₂ reduction, synthesized by an electrostatic self‐assembly approach is reported. First‐principle calculation and in situ X‐ray photoelectron spectroscopy measurement reveal that the delocalized electrons in GDY can hybrid with the empty orbitals in TiO₂ within the TiO₂/GDY network, leading to the formation of an internal electric field at the interfaces, pointing from GDY to TiO₂. The theoretical simulation further implies strong chemisorption and deformation of CO₂ molecules upon GDY, which can be verified by in situ diffuse reflectance infrared Fourier transform spectroscopy. These effects, in combination with the photothermal effect of GDY, result in enhanced charge separation and directed electron transfer, enhanced CO₂ adsorption and activation as well as accelerated catalytic reactions over the TiO₂/GDY heterostructure, thereby resulting in significantly improved CO₂ photoreduction efficiency and meanwhile with remarkable selectivity. This work demonstrates that GYD can function as a highly effective cocatalyst for solar energy harvesting and may be used in other catalysis processes.     

Tuning the Electronic Bandgap of Graphdiyne by H-Substitution to Promote Interfacial Charge Carrier Separation for Enhanced Photocatalytic Hydrogen Production

Graphdiyne (GDY), which features a highly π-conjugated structure, direct bandgap, and high charge carrier mobility, presents the major requirements for photocatalysis. Up to now, all photocatalytic studies are performed without paying too much attention on the GDY bandgap (1.1 eV at the G₀W₀ many-body theory level). Such a narrow bandgap is not suitable for the band alignment between GDY and other semiconductors, making it difficult to achieve efficient photogenerated charge carrier separation. Herein, for the first time, it is demonstrated that tuning the electronic bandgap of GDY via H-substitution (H-GDY) promotes interfacial charge separation and improves photocatalytic H₂ evolution. The H-GDY exhibits an increased bandgap energy ( ≈ 2.5 eV) and exploitable conduction band minimum and valence band maximum edges. As a representative semiconductor, TiO₂ is hybridized with both H-GDY and GDY to fabricate a heterojunction. Compared to the GDY/TiO₂, the H-GDY/TiO₂ heterojunction leads to a remarkable enhancement of the photocatalytic H₂ generation by 1.35 times under UV–visible illumination (6200 µ mol h⁻¹ g⁻¹) and four times under visible light (670 µ mol h⁻¹ g⁻¹). Such enhancement is attributed to the suitable band alignment between H-GDY and TiO₂, which efficiently promotes the photogenerated electron and hole separation, as supported by density functional theory calculations.     

Rechargeable Li?CO2 Batteries with Graphdiyne as Efficient Metal-Free Cathode Catalysts

A rechargeable Li CO₂ battery is one of the promising power sources for utilizing the greenhouse gas CO₂ in a sustainable approach. However, highly efficient catalysts for reversible formation/decomposition of insulating discharge product, Li₂CO₃, are the main challenge, which can boost the cycle stability. Herein, 2D single-atom-thick graphdiyne (GDY) with abundant acetylenic bond sites is prepared by a bottom-up cross-coupling reaction strategy and used as metal-free catalysts for reversible Li CO₂ batteries. The prepared GDY has a rich diacetylenic unit and atomic-level in-plane pores in the network, which can chemically adsorb the CO₂ molecules and easily promote the Li⁺ diffusion and thereby resulting in uniform nucleation and reversible formation/decomposition of the discharge product. The GDY hybrid cathodes show a small overpotential gap of 1.4 V at a current density of 50 mA · g⁻¹, a high full discharge capacity of 18 416 mAh · g⁻¹ at 100 mA · g⁻¹, and outstanding long-term stability of 158 cycles at 400 mA · g⁻¹ with a curtailing capacity of 1000 mAh · g⁻¹. Furthermore, a flexible belt-shaped Li CO₂ battery is fabricated as a proof of concept with a high gravimetric energy density of 165.5 Wh · kg⁻¹ (based on the mass of the whole device) as well as excellent mechanical flexibility.     

石墨炔及其衍生物在钙钛矿太阳能电池的应用

钙钛矿太阳能电池(PSCs)因具有高效率、可溶液加工和低成本等优点受到了人们广泛的关注。然而，在PSCs的各个功能层及界面之间存在缺陷非辐射复合、界面接触不良和薄膜质量较差等问题，阻碍了PSCs光电转换效率和稳定性的提高。相较于石墨烯，含有sp杂化碳原子的石墨炔具有独特的三角微观结构、天然的带隙、超高的载流子迁移率以及优异的光电和机械性能，成为光电能源领域重要的候选材料。综述了石墨炔及其衍生物在PSCs的电子传输层、空穴传输层以及光吸收层中的应用，重点探讨了石墨炔及其衍生物在功能层及其界面中钝化缺陷、改善薄膜形貌和界面接触、提高载流子传输等方面的作用。最后，对石墨炔及其衍生物在PSCs领域中的发展提出了展望。     

Synthesis and Applications of Graphdiyne‐Based Metal‐Free Catalysts

The development of carbon materials offers the hope for obtaining inexpensive and high‐performance alternatives to substitute noble‐metal catalysts for their sustainable application. Graphdiyne, the rising‐star carbon allotrope, is a big family with many members, and first realized the coexistence of sp‐ and sp²‐hybridized carbon atoms in a 2D planar structure. Different from the prevailing carbon materials, its nonuniform distribution in the electronic structure and wide tunability in bandgap show many possibilities and special inspirations to construct new‐concept metal‐free catalysts, and provide many opportunities for achieving a catalytic activity comparable with that of noble‐metal catalysts. Herein, the recent progress in synthetic methodologies, theoretical predictions, and experimental investigations of graphdiyne for metal‐free catalysts is systematically summarized. Some new perspectives of the opportunities and challenges in developing high‐performance graphdiyne‐based metal‐free catalysts are demonstrated.