Design And Preparation Of Graphitic Carbon Nitride Based Photocatalysts And Their Photocatalytic Performance

Photocatalysis is a promising and sustainable strategy to overcome the shortage of fossil fuels and solve the related environmental issues.Developing semiconductor photocatalytic systems is a promising strategy for solar energy conversion.However,the overall low efficiency of photocatalytic conversion systems is still a great challenge for industrial applications.Graphitic carbon nitride(g-C₃N₄)has emerged as a hopeful metal-free visible-light photocatalyst owing to its nontoxicity,abundance,stability,and chemical tenability.But,the insufficient light absorption and fast charge carrier recombination is still seriously restricting the photocatalytic performance of g-C₃N₄.In this paper,the photocatalytic performance of g-C₃N₄ is improved through the following methods.Firstly,g-C₃N₄ was co-doped with phosphorus and protons through a facile one-pot process by direct calcination of the mixture of urea and urea phosphate.The phosphorus and protons co-doped g-C₃N₄ shows superior photocatalytic performance,not only in degradation of Rh B,but also in H₂ evolution under visible light irradiation.The roles of phosphorus and protons were deduced by comparative experiments and extensive characterization in detail.The results show that the doped phosphorus can effectively reduce the band gap to increase the utilization of visible light,and the doped protons can increase the separation efficiency of photon-generated carriers.Surface plasmon resonance(SPR)of plasma metal is a phenomenon that can help photocatalysts absorb visible light and has been widely used in the field of photocatalysis.The hot electron injection is an important factor for enhancing photocatalytic performance of the plasmonic metal-semiconductor architecture.The barrier height between the plasmonic metal and the semiconductor limited the hot electrons injection.Constructing the Ag_xAu_1-x/PCN systems as SPR effect assisted photocatalysts,and investigating the effect mechanisms of the barrier between semiconductor and plasmonic metal for hot electrons injection.The doping of phosphorus reduces the conduction band position of the g-C₃N₄,which directly affects the barrier between the metal and the semiconductor.Simultaneously the alloying of the plasmonic metal nanoparticles enhances the contact between the metal and the semiconductor,and improves the contact barrier.Through optimizing the barrier,the hot electrons can be efficiently injected into the semiconductor and utilized in the photocatalytic reactions,which greatly enhance the photocatalytic H₂ evolution performance.In addition,rapid recombination of photogenerated carriers in g-C₃N₄ greatly limits its applications.Construction of heterojunctions can effectively solve this drawback,but will inevitably lower redox ability of photogenerated carriers,reducing light utilization efficiency.A new Z-scheme ferroelectric-Ba Ti O₃/Au/g-C₃N₄heterojunction photocatalyst with extra surface plasmon resonance(SPR)and ferroelectric effects was successfully developed.Due to the synergy of these advantages,this ternary photocatalytic system shows the significantly enhanced generation and separation efficiency of photogenerated carriers and the high reduction ability of elections.It possesses high photocatalytic activity in both Rh B degredation and H₂ evolution.These achievements provide novel perspective for understanding charge transfer mechanisms and new insights into rationally designing efficient g-C₃N₄ based photocatalysts.