Rational G-C₃N₄ Catalysts Design Based On The Electronic Behavior Of The Solid-solid Interface

Catalytic science is considered to be an important surface science of physics and chemistry.And the solid surface theories have provided abundant proofs and ideas for the rational design of industrial catalysts.However,more and more studies have shown that the solid-solid interface of catalyst also has a huge impact on the activity and selectivity of the catalytic reactions.Specifically,charge rearrangement,space charge transfer,and lattice disorder near the solid-solid interface can cause huge changes in the electrical properties and band structures of the two hybrid solid species,thereby changing the performance of the catalyst.In this paper,the fundamentals of solid-solid interface is utilized to study the interfacial electric behaviors of graphite carbon nitride(g-C3N4).Besides,photocatalysts and heterogeneous catalysts based on g-C3N4 are rationally designed,for the development of the highly efficient photocatalysts for environmental treatment and heterogeneous catalysts for selective isoprene hydrogenation.The main contents of the thesis include:1.The self-hybrided hollow double-layer g-C3N4/g-C3N4 nanocages were prepared from the deep eutectic solvent precursors for the first time,using the intermolecular hydrogen bond network in the self-assembled urea-thiocyanate complex.The outer layer of the nanocage is CNH with high polymerization degree,while the inner layer is CNL with low polymerization degree.Thus,the space charge transfer between CHL/CNH interface generates a solid internal electric field within the wall of CN2U1AT nanocages,which promotes directional transport of the photogenerated electron-hole pairs to the opposite sides of CN2U1AT nanocages.Thus,the recombination of photo-generated charge carries are weakened.The obtained CN2U1AT photocatalyst exhibited ultra-high rhodamine B degradation and water splitting activity under visible light.By designing a thin-layer and high-interface-contact hybrid photocatalyst,a highly effective and stable electric field in solid phase was constructed.This strategy remarkably enriched the theory of structure-activity relationship of photocatalysts,thereby providing ideas for rational photocatalyst design based on internal electric field.2.The mesoporous sulfur-doped graphite carbon nitride(MSCN)carriers with high specific surface area were prepared by calcine the self-assembled urea-thiourea complex.The single-site Ni catalyst was prepared by embedding the isolated Ni into the six-folded cavities of the MSCN supports though anti-Ostwald ripening process.The p-π conjugated electron transfer deriving from S impurities modulates the electronic properties of the isolated Ni atoms,thereby precisely adjusting the mono-olefin selectivity in the isoprene hydrogenation reaction on Ni catalyst.The obtained Ni/MSCN-4 showed a hydrogenation rate of 460 mL·gNi-1·h-1 under the selectivity of 95%,which was 65.2 times that of the industrial Ni catalyst under similar selectivity.By studying the contribution of sulfur impurities in the carrier to the catalytic hydrogenation performance,we developed the theory of"catalytic remote control mechanism"promoted by the impurities in carriers,and proposed a more universal"Electronic heterophase interaction"(EHI)theory.It will provide ideas for the design of efficient industrial catalysts.