Synthesis And Study Of Graphitic Carbon Nitride?g-C₃N₄?-Based Photocatalysts For Photolysis Of Water Into Hydrogen

As the growing issues of global energy and environment,it is imperative to explore a renewable energy source that fails to use fossil fuels and produce harmful gas.At present,solar-driven hydrogen?H₂?production from water is reckoned as one of the most ideal tactics by light-irradiated particulate photocatalysts.The heart of photocatalytic technology is catalysts.Among the previously reported semiconductors,carbon nitride?g-C₃N₄?as a metal-free semiconductor has sparked considerable attention on account of its excellent physicochemical stability,appropriate bandgaps and low cost.However,the photoactivity of bulk g-C₃N₄?BCN?is restricted by the marginal visible-light absorption??<460 nm?,small specific area and rapid recombination of charge carriers.Presently,various of approaches have been developed to boost the photocatalytic activity including to element doping,engineering nanoarchitectures and organic copolymerization,etc.Based on the major drawbacks of g-C₃N₄,two approaches for ameliorating photoactivity of g-C₃N₄ are proposed.To further gain insight into microstructures,optical absorption ability,the photocarriers behavior and photocatalytic mechanism of g-C₃N₄,a series of measurements were performed.The photocatalytic ability was evaluated by recording the H₂ production output.Main contents of the paper are as follows:1.Inspired by Schiff-base chemistry reaction,the introduction of C=C skeleton into framework of g-C₃N₄ was successfully constructed.The as-prepared samples were tested by XRD,FT-IR,¹³C-NMR,UV-Vis DRS,PL,etc.Our work firstly reported a simple and efficient strategy for control of C self-doping site in the matrix of g-C₃N₄for enhancing visible-light photocatalytic H₂ production.Results exhibited that the incorporation of C=C skeleton into the framework of g-C₃N₄ could not only extend optical absorption to near infrared?NIR?region,but also remarkably boost the separation of photoinduced excitons.This work sheds light on a subtle molecular-tailored protocol for controlling carbon self-doping site of the g-C₃N₄.2.Inspired by natural hydrogenases?H₂ases?,a semiconductor-molecular photocatalytic system?SMPS?consisting of g-C₃N₄ and phytic-acid nickel?PA-Ni?complex was prepared.To unambiguously confrim molecular structure of this system,a full characterization using Raman spectra,XRD,FT-IR,¹³C solid-state NMR spectra was performed.The light absorption capacity of this system was analyzed by UV-Vis DRS.To gain insights into the photocarrier behavior,surface photovoltage tests,photoelectrochemical measurements and DMPO-·O^2-spin-trapping EPR tests were performed.To understand the role of PA-Ni complex in this system,DFT calculation also was carried out.To analyze electron transfer path,we have further conducted the photoredox tests through the in-situ photodeposition of Pt at?>420 nm and?=940nm,respectively.This system shows excellent activity at?=940 nm,which is unprecedent in SMPSs.Our results show that the PA-Ni species drastically accelerates interface charge transfer and lowers activation energy,besides efficiently absorbing more solar flux in the NIR region.This work sheds light on feasible avenues to prepare stable,cheap,highly active and NIR-harvesting photosystems toward scalable solar-to-H₂ production.