Functionalized Graphite Nitride Carbon Preparation And Photocatalytic Hydrogen Production From Water Splitting

The search for highly active photocatalysts has been a research hotspot and a common challenge in the current field,mainly because of their broad prospects for applications in renewable energy and clean environments.To date,many impressive photocatalytic materials have been explored and have shown relatively high photoreactivity.However,the increasingly unbalanced energy structure forces us to explore new materials and develop new strategies to increase the reactivity of known potential photocatalysts.Based on the above analysis,we have different functionalization of the new non-metallic semiconductor catalyst g-C₃N₄ to expand its application in renewable energy and clean environment.The main work is as follows:?1?Based on the fact that nitrogen defective can greatly affect the electronic structure and the properties of photo-excited charge transmission and plays a substantial role in photocatalysis,defect induced graphite nitride carbon(g-C₃N_4-x?X?/NiS₂)was synthesized by a facile one step with sodium hydroxide-assisted route in this paper.The photocatalytic activity of nitrogen defective g-C₃N_4-x?0.1?/NiS₂ composite photocatalysts exhibited much more high activities,namely,the maximum amount of H₂ production was reached up to 143.5?mol under continuous visible light irradiation for 5 h,which is about 72 times of pristine g-C₃N₄ photocatalyst and two times of g-C₃N₄/NiS₂ composite photocatalysts.Such high enhanced abilities were greatly attributed to the nitrogen defective on the photocatalysts.Some necessary characterizations such as SEM,TEM,XPS,XRD,BET,FTIR,UV–vis diffuse reflectance spectroscopy?DRS?,photocurrent and transient fluorescence etc.were conducted and the results of which were in fully congruent with each other.Furthermore,the possible reaction mechanism over nitrogen defective g-C₃N_4-x?0.1?/NiS₂ composite photocatalyst under visible light irradiation was proposed.?2?Here,an available strategy of nitrogen defects sponge from g-C₃N₄ nanosheets is successfully designed and the nitrogen defective ultrathin graphitic-phase nanosheets are properly prepared.Moreover,a layer of Ni-Bi-Se complex is effectively modified on the basis of appropriate nitrogen defective ultrathin graphitic-phase nanosheets and a more efficient dye-sensitized photocatalytic H₂ evolution is obtained.In addition,in need of special note is that the density of nitrogen defects on g-C₃N₄ photocatalyst can be controlled and adjusted by means of barium hydroxide dosage.Besides the high H₂ yield,the Ni-Bi-Se complex modified nitrogen defective ultrathin graphitic-phase nanosheets are very stable in the process of photocatalytic hydrogen production.A series of characterization studies such as SEM,XRD,TEM,EDX,XPS,UV–vis DRS,FTIR,transient fluorescence and electro-chemistry etc.show that the more active sites appears and the efficiency of photogenerated charge separation is improved due to the introduction of surface N vacancies and Ni-Bi-Se complex doping.The results of which is well mutual corroboration with each other.Based on above results,a possible reaction mechanism was proposed too.?3?In this work,we fabricated a series of ternary CoPS and g-C₃N₄ composite materials by using cobalt,phosphorus and sulfur as donors and g-C₃N₄ as underlying support or substrate,respectively.As expected,the obtained CoPS?x?/g-C₃N₄ catalysts exhibited obviously enhanced photocatalytic hydrogen evolution activity and the corresponding results of hydrogen production were measured in different pH reaction system by using offline statistics.Specifically,the CoPS?0.25?/g-C₃N₄ catalysts reveals a remarkable hydrogen production of 14.12 mmol/g in an EY sensitized 15%?v/v?TEOA aqueous solution under visible light irradiation,which attributes to the formed interfaces between CoPS and g-C₃N₄ with strong bonding,electronic interactions or synergistic effects that can constitute more active centers than individual component.?4?Here,we demonstrated that Ar plasma-treated Ni₃C_1-x-x nanoparticles-decorated ultra-thin porous g-C₃N₄ nanosheets with C-rich system display a better catalytic activity of hydrogen production,which is much higher than that of traditional g-C₃N₄ nanosheets and g-C₃N₄/Ni₃C.C-rich aromatic monomer 2,4,6-trihydroxy-1,3-diazine show remarkable effects on modifying the electronic structure of g-C₃N₄ as shown in UV–visible absorption spectra,XPS results and Mott–Schottky plots.Benefit from better wettability,Ar plasma-treated Ni₃C nanoparticles can be in full contact with the solution and it can also provide sufficient active sites and transport channels due to the changes of the crystal phase interface.By further optimizing the reaction parameters,the amount of H₂ evolution could reach up to 13500.2?mol/g in 5 hours.This design may offer new direction to exploit metal carbides as noble-metal-free co-catalysts for high-efficiency and low-cost g-C₃N₄-based photocatalytic water splitting.