| In recent years,with the increasing emphasis on energy crisis and environmental pollution issues,the search for clear,efficient and environmentally friendly energy source has become the top priority to solve this problem.As an excellent new type energy,hydrogen energy can not only solve the energy crisis well,but also effectively avoid the environmental pollution caused by fossil fuel combustion,which attracted the the attention of researchers all over the world.Among several approaches of hydrogen production,water splitting,especially ones driven by electritiy and solar energy,has become a hot topic because of its merit of atomic economy.Graphitic carbon nitride(g-C3N4)is a promising class of materials catalyzing photocatalytic water splitting.However,its practical applications in photocatalysis is strictly hindered by the low surface area,poor light harvesting capability and detrimental recombination of photoexcited electron-hole pairs.The surface modification of g-C3N4 by introducing defects is regarded as one of the effective ways to migrate these challenges.However,the manipulation effect is heavily dependent on the types,abundance and spatial distribution of the as-introduced defects.In addition,as an alternative to noble metal electrocatalysts candidates,the family of perovskite oxides is a promising class of catalysts for both electrode reactions of hydrogen evolution(HER)and oxygen evolution(OER).However,there still has huge room remaining for improving the activity of perovskite,which necessitates sophisticated structural engineering and critical tailoring of catalytically active sites to break this bottleneck.Aiming to solve these two major problems,in this work,the structure regulation has been applied to g-C3N4-based photocatalyst and LaFeO3-based electrocatalyst based on various unique strategies.The main research contents are as follows:(?)In the study of photocatalytic water splitting:(1)Using melamine as precursor and metal hydride(i.e.,CaH2)as active agent,we facilely incorporated different types of intrinsic defect(i.e.,nitrogen(N)vacancies,surface-absorbed O species and cyano groups(-C?N))into g-C3N4 within one single step.The interaction between melamine and CaH2 during the proposed one-pot annealing process resulted in the homogeneous distribution of defects with high concentration across the porous framework.(2)From the view of electronic structure,via the collaboration with N vacancies,surface-absorbed O species and-C?N defects,the as-prepared material exhibits narrower bandgap,promoted photoexcited electron-hole separation and facilitated charge transfer.In the perspective of structural engineering,such fabrication method weakened the long-range ordered structure and strengthened the thermal polycondensation of precursor,which further enlarged the BET surface area and created the massive porosity.(3)Therefore,under the combined action of N vacancy,O insertion and-C?N defect,the MM-H materials prepared by one-step method had significantly enhanced photocatalytic hydrogen production performance(1305.9 ?mol·h-1·g-1),while the performance of CN-H materials treated with CaH2 and untreated block g-C3N4 were 617.3 ?mol·h-1·g-1 and 178.2?mol·h-1·g-1 respectively.The present work could open up a new horizon for designing highly efficient g-C3N4-based catalysts.(?)In the study of electrocatalytic water splitting:(1)A facile two-step manipulation(in-situ exsolution and post-sulfurization)strategy was proposed and applied on LaCo0.2Fe0.8O3(LCF)perovskite parent,during which the modality and spatial immersion of B-site cobalt(Co)were tuned at nanoscale proximity accordingly(i.e.,lattice Co(?)-segregated Co-embedded CoS2).(2)According to the above strategies,the as-prepared catalyst(S-LCF)obtains an emergent oxygen deficient microstructure seamlessly pinned with uniformly distributed CoS2 nanoparticles(NPs),which demonstrates significantly enhanced performance toward both OER(?=370 mV at 10 mA·cm-2)and HER(?=200 mV at 10 mA·cm-2),and shows a good stability in overall water splitting. |
PDF Full Text Request