| Solar photocatalytic water splitting for hydrogen evolution is an effective way to alleviate the increasingly serious global energy and environmental crisis.Tantalum nitride（Ta3N5）has a narrow band gap（2.1 eV）and its light absorption can be extended to 600nm.It is one of the most promising candidate materials for visible-light photocatalytic water splitting for hydrogen evolution.Since 2002,the photocatalytic hydrolysis of water into hydrogen of Ta3N5 was reported for the first time.People expect to achieve efficient hydrolysis of water into hydrogen through various strategies,such as ion doping,nitriding control,loading cocatalyst,controlling nanostructure and constructing interface structure.However,up to now,the realization of efficient photocatalytic hydrolysis of water into hydrogen of Ta3N5 still faces important challenges.Considering that the photocatalytic process occurs on the catalyst surface,the core-shell structure is designed to reduce material cost.Synthesis of SiO2@Ta3N5photocatalytic materials with core-shell structure by template method.SiO2has relatively low cost,easy control of morphology and size,good dispersion and high light transmittance,so it is suitable for using as core material.The bifunctional cocatalyst is further synergistically modified on the surface of the shell Ta3N5 to achieve efficient photocatalytic hydrolysis of water into hydrogen.Firstly,the preparation process of monodisperse SiO2 nanoparticles by St（?）ber method is optimized,the amount of ammonia is adjusted to 1.3 m L,and heated in water bath at 50℃for 6 hours,so that SiO2 nanoparticles with uniform dispersion diameter of25-30 nm are prepared.Secondly,the preparation process of core-shell SiO2@Ta3N5nanoparticles is established,the optimized process conditions are as follows:Si-Ta ratio（m SiO2:m Ta2O5）is 5:2,dosage of 0.5 M Na OH is 0.25 m L,nitriding temperature is850℃,nitriding time is 3 h,and the core-shell SiO2@Ta3N5 nanospheres（about 25-30nm）with good dispersity can be obtained.Finally,the surface modification of SiO2@Ta3N5 nanoparticles is studied by one-step photo deposition method.The results show that compared with SiO2@Ta3N5(0.02μA·cm-2),the photocurrent(0.08μA·cm-2)of 0.0067%Pd-0.0333%Ru co-modified SiO2@Ta3N5 is increased to 4 times,which proves that Pd-Ru co-modified SiO2 has synergistic effect and effectively inhibits photo-generated carrier recombination.Solar photocatalytic water splitting for hydrogen evolution is an effective way to alleviate the increasingly serious global energy and environmental crisis.Tantalum nitride（Ta3N5）has a narrow band gap（2.1 eV）and its light absorption can be extended to 600nm.It is one of the most promising candidate materials for visible-light photocatalytic water splitting for hydrogen evolution.Since 2002,the photocatalytic hydrolysis of water into hydrogen of Ta3N5 was reported for the first time.People expect to achieve efficient hydrolysis of water into hydrogen through various strategies,such as ion doping,nitriding control,loading cocatalyst,controlling nanostructure and constructing interface structure.However,up to now,the realization of efficient photocatalytic hydrolysis of water into hydrogen of Ta3N5 still faces important challenges.Considering that the photocatalytic process occurs on the catalyst surface,the core-shell structure is designed to reduce material cost.Synthesis of SiO2@Ta3N5photocatalytic materials with core-shell structure by template method.SiO2 has relatively low cost,easy control of morphology and size,good dispersion and high light transmittance,so it is suitable for using as core material.The bifunctional cocatalyst is further synergistically modified on the surface of the shell Ta3N5 to achieve efficient photocatalytic hydrolysis of water into hydrogen.Firstly,the preparation process of monodisperse SiO2 nanoparticles by St（?）ber method is optimized,the amount of ammonia is adjusted to 1.3 m L,and heated in water bath at 50℃for 6 hours,so that SiO2 nanoparticles with uniform dispersion diameter of25-30 nm are prepared.Secondly,the preparation process of core-shell SiO2@Ta3N5nanoparticles is established,the optimized process conditions are as follows:Si-Ta ratio（m SiO2:m Ta2O5）is 5:2,dosage of 0.5 M Na OH is 0.25 m L,nitriding temperature is850℃,nitriding time is 3 h,and the core-shell SiO2@Ta3N5 nanospheres（about 25-30nm）with good dispersity can be obtained.Finally,the surface modification of SiO2@Ta3N5 nanoparticles is studied by one-step photo deposition method.The results show that compared with SiO2@Ta3N5(0.02μA·cm-2),the photocurrent(0.08μA·cm-2)of 0.0067%Pd-0.0333%Ru co-modified SiO2@Ta3N5 is increased to 4 times,which proves that Pd-Ru co-modified SiO2 has synergistic effect and effectively inhibits photo-generated carrier recombination.Pd and PdO/RuO2 are used to co-modify the surface of core-shell structure SiO2@Ta3N5,and a bifunctional local heterogeneous interface is constructed.Compared with SiO2@Ta3N5,the interfacial resistance of Pd/Ta3N5 and PdO/Ta3N5 is increased,electron transfer resistance at Pd/Ta3N5 and PdO/Ta3N5 interfaces increases.The impedance of the Ta3N5 modified by RuO2 is unchanged.Pd and PdO/RuO2 respectively reduces the overpotential of HER and OER,it is favorable for promoting photocatalytic water splitting to produce hydrogen and oxygen.Through Pd/PdO/RuO2 co-modification,the performance of photocatalytic decomposition of aquatic hydrogen was significantly improved(473.52μmol·g-1·h-1),which was 2.8 times higher than that of basic SiO2@Ta3N5(165.74μmol·g-1·h-1).The research shows that the construction of the core-shell structure and the synergistic strategy of surface bifunctional modification provide a new path for the further development of new high-performance Ta3N5-based nanomaterials for photocatalytic water splitting and hydrogen evolution.On the basis of previous experimental research,in order to realize the multivariate synergistic modification of Ni-Pd-Ru and further improve the performance of SiO2@Ta3N5 nanophotocatalytic materials,the influence of the relative proportion of modifiers,modification methods and other process conditions on the photocurrent of the samples were explored.The results show that Ni-impregnated nitriding and oxiding post-treatment contributes to the improvement of photocurrent.Under acidic condition,the photocurrent value of Ni-Pd-Ru co-modified sample is the highest,which lays an experimental foundation for further studing of Ni-Pd-Ru synergistic modification.On the basis of previous experimental research,in order to realize the multivariate synergistic modification of Ni-Pd-Ru and further improve the performance of SiO2@Ta3N5nanophotocatalytic materials,the influence of the relative proportion of modifiers,modification methods and other process conditions on the photocurrent of the samples were explored.The results show that Ni-impregnated nitriding and oxiding post-treatment contributes to the improvement of photocurrent.Under acidic condition,the photocurrent value of Ni-Pd-Ru co-modified sample is the highest,which lays an experimental foundation for further studing of Ni-Pd-Ru synergistic modification. |
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