Graphdiyne Based Electrocatalysts:Controllable Synthesis And Catalytic Performances

Graphdiyne?GDY?is a novel carbon allotrope,containing sp and sp² co-hybrid carbons,in which each benzene ring is connected by six diacetylene bonds,forming a two-dimensional planar structure.The GDY features many unique properties,including large conjugated system,natural pores,carbon chemical bond,semiconducting properties,and chemical and thermal stabilities.Owing to these fascinating properties,GDY exhibits great potential applications in catalysis,energy conversion,and other fields.The unique properties of GDY provides a great opportunity for the synthesis and application of novel functional nanomaterials in catalysis and energy conversion fields.In this dissertation,inspired by the unique chemical and electronic properties,and the controllable growth on any substrate surfaces,a series of new GDY-based heterostructured electrodes with different morphologies,high catalytic activities and stabilities have been successfully designed and fabricated.At the same time,combined with theoretical calculations,the electrochemical properties and electrocatalytic reaction mechanisms of these catalysts were studied detailedly.1.The first chapter focuses on the development history of graphdiyne.The structural and electronic properties and the synthetic methods of graphdiyne are described,followed by the review of graphdiyne-based materials and their applications in catalysis,energy conversion and storage fields.2.In the second chapter,the single crystal hydrotalcite-like material?LDH?with multi-active sites and multi-functionality was successfully synthesized.Its morphological and structural properties were characterized.The following electrochemical studies showed that the types and contents of metal elements can effectively tune the morphologies and structures of the catalysts,and greatly enhance the electrocatalytic performances of them.In addition,the catalytic mechanism was studied by the combination of experimental and theoretical calculations.3.In this section,we demonstrated a facile and universal strategy for improving catalytic performances through optimizing the atomic ratio of transitional metal sulfides.The optimal material could achieve 10 mA cm^-2 at small overpotentials of 208 mV and68 mV for oxygen evolution and hydrogen evolution,respectively.When being used was used as a bifunctional electrode,it exhibited a very low cell voltage of 1.44 V at 10mA cm^-2,and showed high long-ter stability over 80 h at 100 mA cm^-2.The excellent water splitting performance shed light on the promising potential of such sulfides as a high activity and robust stable electrodes.4.In this chapter,a new strategy has been developed for in-situ intercalation-exfoliation LDH nanosheets using graphdiyne.A three-dimensional"GDY-LDH-GDY"sandwiched nanosheets array electrode was constructed?e-ICLDH@GDY/NF?.Experimental results showed that e-ICLDH@GDY/NF has superior electrocatalytic activities and stabilities in HER and OER,as well as overall water splitting processes.5.In the fifth chapter,an in-situ growing method was employed for the synthesis of ultrathin graphdiyne?GDY?coated iron carbonate hydroxide?FeCH?nanosheets arrays on 3D nickel foam.The obtained electrode was directly used as a three-dimensional integrated electrode in alkaline conditions and exhibited excellent hydrogen evolution reaction?HER?,oxygen evolution reaction?OER?catalytic activities and stabilities.Especially,when being used as a bifunctional electrode for overall water splitting,it needed only 1.49 V cell voltage to reach the current density of10 mA cm^-22 and showed excellent long-term stability.6.A three-dimensional multi-level heterostructure?GDY-MoS₂ NS/CF?is synthesized by in situ growth of a graphdiyne nanosheets on the surface of molybdenum sulfide nanosheets.The introduction of graphdiyne realizes the transformation of molybdenum sulfide from 2H to 1T phase,which significantly increases the charge transport of the system,reduces the free energy of hydrogen adsorption,and further enhances its intrinsic catalytic activity.Studies have shown that GDY-MoS₂ NS/CF showed excellent HER activity and stability over a wide pH range?0¹4?.For example,under alkaline?pH=14?conditions,it exhibited a better HER activity than commercial20 wt.%Pt/C;and its transient photocurrent is 45.7 times larger than MoS₂.7.Summary and perspective.