通过合理的形貌调控使石墨相氮化碳(g-C3N4)低维化和多孔化,是提高其光催化活性的有效途径.采用高温煅烧方法制备了HCl、HNO3和H2SO4刻蚀的g-C3N4,并对它们进行了结构形貌表征、形成机理探究和光催化降解罗丹明B测试,还给出了活性增强机理.结果显示:酸刻蚀g-C3N4具有和g-C3N4相同的基本晶体结构,但是呈薄片状,且表面出现了大量纳米孔,这些孔是由无机酸阻碍前驱体中N—H键参与热缩聚反应所致,按照HCl、HNO3、H2SO4的顺序阻碍作用依次增强,对应的孔径依次增大,结构边缘(C)2—N—H基团的XPS特征峰强度也依次增加;经过40 min光反应,g-C3N4和HCl、HNO3、H2SO4刻蚀的g-C3N4对罗丹明B的降解率分别为45％、56％、52％和95％,H2SO4刻蚀的g-C3N4光催化活性最高;酸刻蚀引起的薄片和多孔结构不仅增加了g-C3N4的比表面积,促进了暗条件下对罗丹明B的吸附,还通过量子限域效应提高了其光吸收能力,拓宽了禁带宽度,有效促进了光生电荷的分离.因此,酸刻蚀克服了g-C3N4的缺点,为探寻其光催化活性的提高方法提供了有价值的启发.%Obtaining low dimension and porosity of graphitic carbon nitride (g-C3N4) through proper morphology control is an effective way to improve its photoactivity. By using high-temperature calcination treatment, g-C3N4 was etched by HCl, HNO3, and H2SO4, respectively. Their surface and structural properties, formation mechanism, and photoactivity of rhodamine B degradation were studied, and the photoactivity enhancement mechanism was proposed. Results show that the basic crystal structure of g-C3N4 underwent trivial changes after acid etching, while flake structure and lots of nanopores were formed, and the nanopores were the result of acid inhibition on the thermal condensation reaction over N—H bond in precursor. The inhibition effect, diameters of the nanopores, and the XPS peak intensity corresponding to marginal (C) 2—N—H group increased in the order of HCl, HNO3, and H2SO4. After 40 minutes, the rhodamine B degradation rates of g-C3N4, g-C3N4 etched by HCl, HNO3, and H2SO4 were 45％, 56％, 52％, and 95％, respectively, among which the g-C3N4 etched by H2SO4 exhibited the best photoactivity. Flake structure and nanopores increased the specific surface area of g-C3N4, promoted the adsorption of rhodamine B under dark conditions, enhanced the light absorption ability, and broadened the band gap through the quantum confinement effect, which effectively accelerated the separation of photogenerated charge. Thus, acid etching overcomes the shortcomings of g-C3N4 and the research results provide some valuable insights to the exploration of photoactivity enhancement methods.
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