熔盐法制备K^+-g-C3N4及其光催化降解有机污染物性能

Preparation of potassium ion doped graphite carbon nitride via molten salt method and its photocatalytic mineralization ability of organic pollutants

采用熔盐法制备了能级位置可控的钾离子掺杂石墨相氮化碳催化剂(g-C3N4),并考察了其在可见光下降解罗丹明B(RhB)性能.采用XRD、UV-Vis、XPS、N2吸附、PL、EIS等手段对催化剂进行了表征.结果表明,钾离子的引入降低了催化剂粒径尺寸,提高了比表面积,改善了光生电子-空穴对的分离效率.不仅如此,通过控制钾离子掺杂量可以实现催化剂的能级位置在一定范围内的任意调变,使有机污染物的氧化降解反应从·O2^-单一氧化剂反应变成·OH和·O2^-双氧化剂反应,大大提高了降解率.制备的钾离子掺杂g-C3N4的RhB降解速率常数达到0.022min^-1,是纯g-C3N4的5倍.不仅如此,通过对能级位置的调控,制备的催化剂对其他多种有机污染物如甲基蓝,苯酚等的降解率也有显著提高.

A band gap-tunable potassium doped graphitic carbon nitride(g-C3N4)with enhanced RhB degradation ability was prepared via molten salt method.X-ray diffraction(XRD),UV-Vis spectroscopy,X-ray photoelectron spectroscopy(XPS),N2 adsorption,Photoluminescence(PL)and Electrochemical impedance spectra(EIS)were used to characterize the prepared catalysts.The addition of potassium inhibited the crystal growth of graphitic carbon nitride,enhanced the surface area and increased the separation rate of photogenerated electrons and holes.In addition,by controlling the potassium ion doping amount,the CB and VBpotentials of graphitic carbon nitride can be adjusted within a certain range,so that the oxidative degradation reaction of organic pollutants changes from single oxidant(·O2^-)reaction to double oxidant(·OH and·O2^-)reaction,leading to the promoted degradation and mineralization ability.The RhB degradation rate constant of as-prepared potassium ion doped catalyst arrived 0.022min^-1,which is 5 times higher than that of neat g-C3N4.Moreover,the degradation rate of the as-prepared catalyst to other organic pollutants,such as methyl blue and phenol,was also significantly improved by tuning the energy level.