Organic Semiconductor Heterojunction Nanoparticles For Efficient Photocatalytic Hydrogen Production

With the proposal of China’s"dual carbon"strategy,the increasement of renewable energy and the reduction of fossil energy in energy supply have become the new requirements in the new era.Hydrogen fuel,as a"zero-carbon fuel",is green and clean,fully in line with the sustainable development.Therefore,the preparation of hydrogen has become one of a hot research area,including the conversion of solar energy into hydrogen energy.Photocatalysis is getting a lot of attention as a technology to direct convert solar energy into chemical energy.Compared with inorganic semiconductors with wide band-gap and low visible light utilization,organic semiconductors have the advantages of adjustable band-gap and strong visible light response,which has great potential in the field of photocatalysis.However,the high exciton binding energy and short exciton diffusion distance are the key factors that limit the photocatalytic hydrogen production rate.The p/n heterojunction can be constructed to provide the driving force for exciton dissociation by using the energy level difference at the donor/acceptor interface.In this work,polymer/non-fullerene molecular bulk heterojunction nanoparticles were prepared as photocatalysts for water splitting,with the photocatalytic activity rationally enhanced via tuning of the donor/acceptor component,the solvent choice and the surfactant.The mechanism of photocatalytic decomposition of water to produce hydrogen and the photocatalytic stability were further explored.The main research contents and conclusions are as follows:（1）A PBDBT-T/ITIC heterojunction nanoparticle photocatalyst was prepared by micro-emulsion method,and the optimal hydrogen production efficiency was evaluated under the full spectral range（320-780 nm,AM 1.5G）.The photocatalytic hydrogen production efficiency reached 103 mmol h^-1 g^-1 when the donor/acceptor mass ratio was optimized at 1:1.5.When the volume ratio of the CF/CB solvents was 1.5:1,the photocatalytic hydrogen production rate was promoted to 130 mmol h^-1 g^-1,which was furtuer increased to 257 mmol h^-1 g^-1 with an AQY of 5.2%at 650nm and the nanoparticle size at 80 nm that was obtained with the presence of 0.7mg/m L of surfactant SBDS.Fluorescence quantum lifetime experiments indicated these strategies can promote the dissociation of exciton and charge transfer to the surface of nanoparticles,thus affecting the efficiency of hydrogen evolution.（2）By introducing the highly-crystallizable non-fullerene acceptor IDMIC-4F into PM6/ITCC-M as the third component,a ternary organic nanoparticle photocatalyst with hydrogen production efficiency up to 307 mmol h^-1 g^-1 was prepared.IDMIC-4F was used to further modify the internal nanoscale morphology of nanoparticles to increase the charge transport channels.Studies on PL and TRPL of the ternary nanoparticles showed that the PL strength decreased and the average life of nanoparticles shortened after the addition of IDMIC-4F,supporting more effective exciton dissociation and charge transfer,and thus improving the hydrogen generation rate.In addition,the addition of the highly-crystallizable IDMIC-4F can improve the photocatalytic stability,and maintain a high hydrogen production efficiency after a continuous 40 h hydrogen production experiment.