RESUMEN
Modifying the polymeric carbon nitride (CN) with organic molecules is a promising strategy to enhance the photocatalytic activity. However, most previously reported works show that interchain embedding and edge grafting of the organic molecule can hardly be achieved simultaneously. Herein, we successfully synthesized organic molecule bifunctionalized CN (MBCN) through copolymerization of melon and sulfanilamide at a purposely elevated temperature of 550 °C. In MBCN, the edge grafted and interchain embedded benzene rings act as the electron-donating group and charge-transfer channel, respectively, rendering efficient photocatalytic H2 O2 production. The optimal MBCN exhibits a significantly improved non-sacrificial photocatalytic H2 O2 generation rate (54.0â µmol g-1 h-1 ) from pure water, which is 10.4â times that of pristine CN. Experimental and density functional theory (DFT) calculation results reveal that the enhanced H2 O2 production activity of MBCN is mainly attributed to the improved photogenerated charge separation/transfer and decreased formation energy barrier (âµG) from O2- to the intermediate 1,4-endoperoxide (â OOH). This work suggests that simultaneous formation of electron donating group and charge transfer channel via organic molecule bifunctionalization is a feasible strategy for boosting the photocatalytic activity of CN.
RESUMEN
Surface modification has been considered a simple and effective strategy to enhance the photocatalytic activity of polymeric carbon nitride (CN), but resultant difference of energy band structures between the modified surface layer and the unmodified inside in the sample has always been neglected. Herein, maleoyl-modified CN (MaCN) was simply prepared via a dehydration reaction between CN and maleic acid, and exhibits enhanced charge separation, optical absorption, and thus photocatalytic hydrogen evolution activity, relative to the bulk CN. The surface modification causes variation of the band structure, suggesting the difference of band levels between the surface layer with maleoyl-modification and the inside without any modification in MaCN, and the surface layer and the inside with matched band levels form type-II core-shell homojunction to enhance the charge separation. This work expounds a conceptual framework of core-shell homojunction in surface-modified CN photocatalysts.
RESUMEN
Fabrication of homojunctions is a cost-effective efficient way to enhance the photocatalytic performance of polymeric carbon nitride (CN), but the generation of defects upon synthesizing CN homojunctions and their roles in the homojunction fabrication were hardly reported. Herein, nitrogen-deficient CN homojunctions were simply synthesized by calcining dicyandiamide-loaded CN (prepared from urea and denoted as UCN) with dicyandiamide polymerizing into CN (denoted as DCN) and simultaneous formation of nitrogen vacancies in the surface of UCN. Fabrication of the nitrogen-deficient UCN (dUCN)/DCN homojunction depends on the nitrogen vacancy content in dUCN which can tune the energy band structure of dUCN from not matching to matching with that of DCN. The dUCN/DCN homojunction exhibits extended optical absorption and remarkably enhanced charge separation and photocatalytic H2 evolution, compared with UCN and DCN. This work illustrates the pivotal role of defects in fabricating CN homojunctions and supplies a new facile way to synthesize nitrogen-deficient CN.
RESUMEN
Construction of Z-scheme heterojunction (ZCH) is one of the most effective ways to enhance photocatalytic performance of photocatalysts. The direct all-solid-state p-n ZCH shows the best prospect, but its fabrication mechanism, especially function of the interfacial electric field (IEF) was rarely expounded explicitly. Herein, a direct all-solid-state p-n copper indium disulfide/tungsten oxide (CIS/WO) ZCH was prepared through a facile hydrothermal process for the first time. The CIS/WO ZCH exhibits enhanced photocatalytic activity because of significantly accelerated photogenerated charge separation via a Z-scheme charge migration process. The Z-scheme charge transfer pathway is inferred from matched energy band levels of CIS and WO and the IEF is confirmed to play a key role. The CIS/WO ZCH can fast produce singlet oxygen via hole oxidation of superoxide radicals under visible light irradiation, while pure CIS and WO cannot, effectively verifying the Z-scheme charge transfer process. This work illustrates the principle for fabrication of the direct all-solid-state p-n ZCH and function of the IEF, as well as provides a new ZCH.
