Synthesis And Performance Of N-doped Graphene/Carbon-rich C₃N₄ For Photo-Promoted Electrochemical Catalysis

Hydrogen energy is the most promising alternative to fossil energy.At present,the main source of hydrogen energy is photocatalytic or electrocatalytic decomposition of H₂O.The decomposition reaction of H₂O includes hydrogen evolution reaction?HER?and oxygen evolution reaction?OER?.Graphene doping can introduce high active reaction sites,open the band gap,produce the photogenerated electron-hole pairs with light excitation,and improve H₂O decomposition efficiency by coupling photo-electrocatalysis.Distinctive electronegativity and similar atomic radius for elements of C and N afford their allotropic substances composed of these two elements with excellent photo-and electro-chemical performance for energy conversion.To explore the synergism of allotropic substances,carbon-rich C₃N₄?CCN?was in-situ hydrothermally synthesized with the N-doped graphene?NG?grown by chemical vapor deposition?CVD?as the template to prepare the NG/CCN composite.Compared to the NG and CCN,NG/CCN composite exhibits the remarkable enhancement of catalytic activities toward HER,OER and oxygen reduction reaction?ORR?.Particularly,visible light irradiation can significantly improve the catalytic performance of NG/CCN toward the above three reactions.The results concluded from the photoluminescence spectroscopy?PL?,electrochemical impedance spectroscopy?EIS?,transient photocurrent?I-t?and Mott-Schottky plots?MS?confirm that NG/CCN exhibits the improved light-harvesting ability,effective separation of electron-hole pairs,and interfacial charge transfer as compared to the NG and CCN,beneficial to photo-promoted electrochemical catalysis.Then,nitrogen-doped graphene quantum dots?N-GQDs?were combined with NG/CCN via in-situ hydrothermal method to synthesize NG/CCN/N-GQDs.In this paper,the synergism of NG,CCN and N-GQDs for the photo-promoted electrochemical performance was explored by HER,OER,ORR tests and XRD,FTIR and PL characterization.The results show that NG/CCN/N-GQDs composites have better multifunctional electrocatalytic performance than NG and CCN,and their electrocatalytic performance is enhanced under visible light irradiation.Moreover,compared to the NG/CCN,NG/CCN/N-GQDs have selective catalytic performance enhancement for HER,OER and ORR.Our elucidation on the synergism between NG,C₃N₄,and N-GQDs facilitates to reveal the influence mechanism of doping on the catalytic performance of graphene-based carbon materials,and clarify the influence of the microstructural characteristics of graphene-like materials containing C and N elements on their catalytic performance.Moreover,our study revealed the structure-performance-effect principle of synergistic compounding,which pave NG,C₃N₄,and N-GQDs promising applications in microelectronic devices,dual-photoelectric fuel cells,wearable devices,photoelectrochemical batteries,sensors and other fields.