摘要
氢能作为无污染、高能量密度的清洁能源,被视为未来可持续发展的理想能源。光催化技术是缓解能源危机的绿色技术之一,寻找性能优异的光催化产氢材料为当务之急。本工作采用高温煅烧与原位沉积-沉淀法制备了磷酸银负载石墨相氮化碳(Ag_(3)PO_(4)/C_(3)N_(4))二元复合光催化剂,并用于光催化制氢实验,研究了Ag_(3)PO_(4)负载量、牺牲剂种类、牺牲剂添加量对产氢性能的影响,采用XRD、FTIR、XPS、SEM、UV-vis DRS、PL等多种技术对光催化剂进行物理化学结构特征分析。结果表明,Ag_(3)PO_(4)的负载量为4%时,Ag_(3)PO_(4)-4/C_(3)N_(4)产氢量最高,可达218.97μmol,分别是C_(3)N_(4)和Ag_(3)PO_(4)的3.1倍和58.4倍。与甲醇、丙三醇和乳酸相比,三乙醇胺是Ag_(3)PO_(4)/C_(3)N_(4)光催化剂的最佳牺牲剂,然而过量的三乙醇胺不能进一步提升产氢量。在FT-IR光谱中没有观察到明显的Ag_(3)PO_(4)吸收峰,这可能是由于Ag_(3)PO_(4)含量较低所致,随着Ag_(3)PO_(4)负载量的增加,C_(3)N_(4)(002)晶面的衍射峰逐渐减小,反映出Ag_(3)PO_(4)在C_(3)N_(4)表面良好的分散性和Ag_(3)PO_(4)/C_(3)N_(4)复合光催化剂的有效耦合。负载少量Ag_(3)PO_(4)后,C_(3)N_(4)的形貌发生变化,Ag_(3)PO_(4)/C_(3)N_(4)比表面积增大,且Ag_(3)PO_(4)以纳米颗粒形式高度分散于C_(3)N_(4)表面。Ag_(3)PO_(4)/C_(3)N_(4)表现出较高的瞬态光电流强度,证实了C_(3)N_(4)与Ag_(3)PO_(4)形成异质结,有效地增强了Ag_(3)PO_(4)/C_(3)N_(4)中光生电子-空穴对的分离。较大的比表面积、增强的光吸收特征、光生电子-空穴对的有效分离与转移是Ag_(3)PO_(4)/C_(3)N_(4)复合材料高效光催化产氢的重要因素。基于表征和实验结果,提出了Ag_(3)PO_(4)改性C_(3)N_(4)异质结光催化剂的产氢机理。
As a green and eco-friendly clean energy source,hydrogen energy has the advantages of high energy density and no pollution to the environment.Due to the direct utilization of solar energy,photocatalytic water splitting for hydrogen production is a promising technology.g-C_(3)N_(4) could be utilized to achieve hydrogen through water splitting.However,g-C_(3)N_(4) material has some disadvantages such as a small specific surface area,fast recombination of electron and hole pairs generated by photocatalysis,and insufficient photo-responsiveness,which greatly limits its photocatalytic performance.Ag_(3)PO_(4),as one of the new silver-based photocatalysts,has the advantages of high quantum yield and narrow bandgap.Coupling polyhedral Ag_(3)PO_(4) with two-dimensional g-C_(3)N_(4) material to form a heterojunction to enhance photocatalytic stability should be feasible.In this paper,silver phosphate modified graphitic carbon nitride(Ag_(3)PO_(4)/C_(3)N_(4))binary composite photocatalysts were prepared by a high-temperature calcination and in situ deposition-precipitation method,which were employed for photocatalytic hydrogen production.The effects of Ag_(3)PO_(4) loading,the type of sacrificial agents and the amount of sacrificial agent on hydrogen production were studied.Meanwhile,various techniques such as XRD,FI-TR,XPS,SEM,UV-vis DRS,PL,etc.were carried out to analyze the physical and chemical characteristics of the photocatalysts.The results show that when the Ag_(3)PO_(4) mass loading is 4%,the hydrogen production rate of Ag_(3)PO_(4)-4/C_(3)N_(4) is the highest,reaching 218.97μmol,which is 3.1 times and 58.4 times higher than that of C_(3)N_(4) and Ag_(3)PO_(4),respectively.Compared with methanol,glycerol and lactic acid,triethanolamine(TEOA)is the best sacrificial agent for Ag_(3)PO_(4)/C_(3)N_(4) photocatalyst,but an excessive triethanolamine cannot further improve the hydrogen production rate.No obvious absorption peak of Ag_(3)PO_(4) is observed in the FT-IR spectra,which could be due to the low content of Ag_(3)PO_(4).While with the increase of Ag_(3)PO_(4) loading,the diffraction peak of C_(3)N_(4)(002)crystal plane decreases gradually,reflecting an excellent dispersion of Ag_(3)PO_(4) on C_(3)N_(4) surface and an effective coupling of Ag_(3)PO_(4) and C_(3)N_(4).The shift in binding energies of the researched elements indicates a strong interaction between C_(3)N_(4) and Ag_(3)PO_(4).After loading a small amount of Ag_(3)PO_(4),the morphology of C_(3)N_(4) changes from the original rocky block shape to multi-angular sheets,and its specific surface area increases.Moreover,Ag_(3)PO_(4) is highly dispersed on the surface of C_(3)N_(4) in the form of nanoparticles.Ag_(3)PO_(4)-4/C_(3)N_(4) exhibits a high transient photocurrent intensity,confirming that C_(3)N_(4) and Ag_(3)PO_(4) form a heterojunction,effectively enhancing the separation of photo-generated electron-hole pairs in Ag_(3)PO_(4)-4/C_(3)N_(4).The large specific surface area,enhanced light absorption characteristics and effective separation and transfer of photogenerated electron-hole pairs are important factors for efficient photocatalytic hydrogen production of Ag_(3)PO_(4)/C_(3)N_(4) composites.Based on the characterization and experimental results,an S-type heterojunction photocatalytic hydrogen production mechanism is proposed.Under illumination,the cocatalyst H_(2)PtCl_(6) in the reaction solution is reduced to Pt^(0).Due to the SPR effect of Pt-+metal,some e are transferred to Pt^(0),which combines with H to accelerate the photocatalytic hydrogen production reaction 0 rate.At the same time,a small amount of Ag_(3)PO_(4) is irradiated to precipitate Ag as a silver bridge,promoting the-++recombination of e generated by Ag_(3)PO_(4) with h at the VB site of C_(3)N_(4) photocatalyst.The h accumulated by Ag_(3)PO_(4) photocatalyst at VB oxidizes TEOA to TEOA+.This S-shaped heterojunction charge transfer method helps to improve the separation speed of electron-hole pairs and enhance the photocatalytic hydrogen production performance.
作者
敬曼曼
张倩倩
张安超
芦涛
倪飞翔
栗敏
杜海星
JING Manman;ZHANG Qianqian;ZHANG Anchao;LU Tao;NI Feixiang;LI Min;DU Haixing(School of Mechanical and Power Engineering,Henan Polytechnic University,Jiaozuo 454003,China)
出处
《燃料化学学报(中英文)》
北大核心
2025年第3期371-381,共11页
Journal of Fuel Chemistry and Technology
基金
国家自然科学基金(51676064)
河南省自然科学基金(232300420082)
河南理工大学创新型科研团队项目(T2020-3)资助。
关键词
光催化剂
石墨相氮化碳
磷酸银
产氢
异质结
photocatalyst
g-C_(3)N_(4)
Ag_(3)PO_(4)
H_(2)production
heterojunction
作者简介
敬曼曼(1996),女,硕士研究生,研究方向为光催化产氢技术,1272380657@qq.com;Corresponding author:张倩倩(1986),女,博士,硕士生导师,研究方向为大气污染物排放控制与治理、氢能及储能技术,E-mail:zhangqianqian@hpu.edu.cn;Corresponding author:张安超(1981),男,博士,博士生导师,研究方向为能源洁净高效利用与节能减排、光电催化制氢/二氧化碳还原技术,E-mail:anchaozhang@126.com。
