Comprehensive experimental design of phenolic resin-g-C3N4 heterostructure prepared by the ball-milling method for photocatalytic H2O2 production under visible light
[Objective]Hydrogen peroxide(H2O2)is a versatile chemical used for bleaching,sterilization,and environmental remediation and as an energy carrier alternative to oxygen and hydrogen in fuel cells.However,the traditional method of producing H2O2,known as the anthraquinone process,is energy-intensive and produces considerable waste.Therefore,alternative methods such as electricity and light-driven water oxidation reactions have been proposed.In bulk g-C3N4 with a stacked two-dimensional(2D)structure,the position of the conduction band(CB)(-1.3 V vs.NHE)is lower than that of O2 reduction(-0.28 V vs.NHE)while its valence band(VB)(1.4 V vs.NHE)can inhibit the oxidative decomposition of H2O2.In addition,it exhibits high selectivity for H2O2 production due to the sequential formation of superoxo radicals(·O2-)and 1,4-endoperoxide species during photocatalytic reactions.[Methods]Herein,we developed a Z-scheme RF-CN photocatalyst by introducing g-C3N4 into a low-temperature resorcinol-formaldehyde resin.The RF-CN photocatalyst was assembled via ball milling,and its structures and properties were analyzed using different characterization methods and photocatalytic H2O2 production was measured under various conditions.[Results]The results indicated that the resin exhibited a structure resembling Go pieces,with an average diameter of～700 nm,and in RF-CN,resin pieces were distributed on the g-C3N4 surface and interval space between the g-C3N4 layers.Thus,it is obvious that resin pieces were simply attached to the g-C3N4 structure and not incorporated integrally.After mechanochemical treatment,resin pieces were embedded in the g-C3N4 layers to form integrity blocks,as confirmed by the transmission electron microscopy images.In addition,the particle size of resin pieces reduced slightly with some deformation after mechanochemical treatments.H2O2 production tests showed a significant improvement in the production of H2O2 by RF-CN compared with the bare resin and bulk g-C3N4,and the H2O2 yield reached 72.86 μmol after 12 h of visible light irradiation without a sacrificial agent.The corresponding H2O2 production rate of samples exhibited the following order:RF-CN-bm(0.438)＞RF-CN(0.318)＞RF(0.268)＞g-C3N4(0.024),while the dissolution rate of H2O2 by the four catalysts demonstrated the following order:RF-CN-bm(0.005)＜RF-CN(0.006)＜RF(0.008)＜g-C3N4(0.015).This indicates that RF resins can dissolve the produced H2O2 only in limited quantities,thus benefiting H2O2 accumulation.Moreover,introducing g-C3N4 into RF resins could produce C=O(quinone)at 180℃,which is beneficial for photocatalytic H2O2 production.The mechanochemically assembled RF-CN-bm showed the typical photocatalytic properties of a D-A structure,enabling two-electron oxygen reduction.Using optimal ball milling,resin particles were embedded inside the two-dimensional structure of g-C3N4 to form an integrated catalyst and enhance the heterostructure's visible light absorption(＞800 nm).H2O2 generation by RF-CN-bm primarily occurred through two paths:a)O2 reduction by CB e- of g-C3N4 and b)a combination of HO produced by the oxidation of OH- via the VB h+ of RF.In summary,we successfully prepared a Z-scheme RF-CN photocatalyst via mechanochemical treatment,realizing a high yield for H2O2 under visible light without a sacrificial agent.[Conclusions]This study reports useful implications for preparing Z-scheme heterostructure catalysts and provides new insights into the formation of C=O(quinone)in resorcinol-formaldehyde resins.
万方数据
