原位光还原法制备高分散铂沉积多孔氮化碳复合材料及其降解水中4-氟苯酚的高效可见光光催化活性

作为一种新型水中有机污染物,有机氟化物中C–F共价键的键能较大,因而很难通过传统的可见光光催化剂降解.因此,开发高效可见光光催化剂是实现在可见光照射下成功降解水中有机氟化物的关键.作为一种非金属半导体光催化剂,石墨相氮化碳(g-C3N4)因具有可见光响应、环境友好及低成本等优点而广泛应用于水中有机污染物去除.然而,体相层状结构严重限制了g-C3N4的可见光活性.这是由于体相层状结构不利于光生电子的表面迁移,同时增加了光催化反应过程的传质阻力.为了开发一种可重复使用且具有优异可见光活性的光催化剂,进而实现在可见光照射下水中有机氟化物的高效降解及矿化,本文以氯铂酸和多孔氮化碳(pg-C3N4)为前驱体,运用简单的原位光还原法成功制备出一系列高分散铂沉积多孔氮化碳复合材料(Pt/pg-C3N4),而pg-C3N4则是以三聚氰胺为原料采用前驱体预处理法制备.与传统铂沉积石墨相氮化碳(Pt/g-C3N4)复合材料相比,由于多孔氮化碳前驱体具有暴露的几何内外表面,铂纳米粒子可高度分散于其上.因此,铂纳米粒子的电子捕获效应显著增强.另外,与其他传统还原法相比,原位光还原技术还可有效抑制铂纳米粒子的自凝聚.我们对制备的Pt/pg-C3N4复合材料的形貌、孔隙率、相结构、化学组成及光电性质进行了详细表征.结果显示,与传统Pt/g-C3N4复合材料相比,由于多孔微观结构的构建以及高度分散铂纳米粒子的沉积,制备的Pt/pg-C3N4复合材料的BET比表面积显著增大,光吸收能力明显增强,光催化量子效率显著提高.在可见光条件下,初步评价了该复合材料光催化降解水中偶氮染料甲基橙的活性,然后将其进一步应用于水中4-氟苯酚的降解及矿化.结果表明,由于多孔微观结构的构建以及高度分散铂纳米粒子的沉积,所制备Pt/pg-C3N4复合材料具有相当高的可见光光催化活性.结果还显示,所制复合材料具有很高的稳定性,连续使用4次均保持相似的活性.作为一种可见光催化剂,所制Pt/pg-C3N4复合材料有望广泛应用于水中持久性有机污染物的降解以及光催化劈裂水产氢、NO分解和CO2还原等领域.

Fabrication of highly dispersed platinum-deposited porous g-C3N4 by a simple in situ photoreduction strategy and their excellent visible light photocatalytic activity toward aqueous 4-fluorophenol degradation

A series of highly dispersed platinum-deposited porous g-C3N4 (Pt/pg-C3N4) were successfully fab-ricated by a simpleinsitu photoreduction strategy using chloroplatinic acid and porous g-C3N4 as precursors. Porous g-C3N4 was fabricated by a pretreatment strategy using melamine as a raw ma-terial. The morphology, porosity, phase, chemical structure, and optical and electronic properties of as-prepared Pt/pg-C3N4 were characterized. The photocatalytic activity of as-prepared Pt/pg-C3N4 was preliminarily evaluated by the degradation of aqueous azo dyes methyl orange under visible light irradiation. The as-prepared Pt/pg-C3N4 were further applied to the degradation and mineral-ization of aqueous 4-fluorophenol. The recyclability of Pt/pg-C3N4 was evaluated under four con-secutive photocatalytic runs.