| With the development of social industrialization,the over-exploitation of fossil energy has also led to the double crisis of environmental pollution and energy shortage.Finding renewable clean energy to replace fossil energy has always been a problem that we need to pay close attention to and solve.As a renewable and clean energy,hydrogen is rich in resources and does not pollute the environment,so it is the best choice to replace fossil energy.The use of photocatalytic decomposition of water to produce hydrogen is also considered to be an ideal strategy to solve the crisis,but the development of good performance and stable photocatalyst is the core of photocatalytic technology.High-entropy oxides have attracted much attention due to their unique crystal structure,abundant active sites,high temperature phase stability and adjustable specific surface area.However,there are few reports on photocatalytic hydrogen production using high-entropy oxides as photocatalysts.In this paper,the spinel high-entropy oxides were used as the research object,a simple preparation process was designed,and the high-entropy oxides were modified by semiconductor composite modification methods to prepare high-entropy oxides（HEOs）/Ti O2 composites.The effects of Ti O2 content and preparation temperature on the photocatalytic hydrogen production performance were systematically studied.（1）Preparation of（Cr Mn Co Ni Zn）3O4/Ti O2nano-heterojunction and investigation of photocatalytic hydrogen production performance.（Cr Mn Co Ni Zn）3O4 high-entropy oxide was successfully prepared by solution combustion method,and then（Cr Mn Co Ni Zn）3O4/Ti O2 nano-heterojunction was prepared after grinding and calcination.The structure,morphology and hydrogen production performance of the composites were investigated by various characterization.The results show that the heterojunction is formed between（Cr Mn Co Ni Zn）3O4and Ti O2,and the photogenerated carrier separation and mobility are higher,which improves the photocatalytic activity of hydrogen production.When the molar ratio of（Cr Mn Co Ni Zn）3O4 to Ti O2 is 1:10 and the calcination temperature is 500℃,the photocatalytic hydrogen production rate reaches the maximum.The photocatalytic hydrogen production rate of the nano-composite material under visible light reaches 1403.2μmol·h-1·g-1,which is 96 and 2.13 times higher than that of the（Cr Mn Co Ni Zn）3O4 nano-material and Ti O2 nano-particle,respectively.After 3-12 h light stability test,the hydrogen production attenuation rate of the composite was 18.7%,which also showed that the nanocomposite had better light stability than Ti O2.（2）Preparation of（Ti Mn Co Ni Zn）3O4/Ti O2 nano-heterojunction and investigation of photocatalytic hydrogen production performance.The（Ti Mn Co Ni Zn）3O4/Ti O2 nano-heterojunction was prepared by the preparation method in（1）.The heterojunction is confirmed to be formed in the composite material by various characterization means,and the heterojunction provides abundant active sites,thereby improving the problem of high recombination efficiency of photogenerated carriers.The utilization rate of visible light is increased,and the photocatalytic hydrogen production activity is improved.When the molar ratio of（Ti Mn Co Ni Zn）3O4 to Ti O2 is1:30 and the secondary calcination temperature is 450℃,the hydrogen production rate of the nano-composite material under visible light reaches 1304.5μmol·h-1·g-1,which is 85 times and1.98 times of that of（Ti Mn Co Ni Zn）3O4 and Ti O2,respectively.After the light stability test,the hydrogen production attenuation rate of the composite was 11%,which also showed that the composite had better light stability than Ti O2.（3）Preparation of（Ti Cr Mn Co Ni）3O4/Ti O2 nano-heterojunction and investigation of photocatalytic hydrogen production performance.The（Ti Cr Mn Co Ni）3O4/Ti O2 nano-heterojunction was prepared by the preparation method in（1）.Through various characterization means,it is determined that a heterojunction is formed in the composite material,the separation and migration efficiency of photogenerated carriers is faster,the utilization rate of visible light is improved,and the service life of the photogenerated carriers is also improved.After secondary calcination,more active sites are exposed on the surface of the composite material,and the photocatalytic activity is improved.When the molar ratio of（Ti Cr Mn Co Ni）3O4 to Ti O2 is 1:40and the secondary calcination temperature is 550℃,the photocatalytic hydrogen production rate of the nanocomposite reaches 1449μmol·h-1·g-1 under visible light,which is 98 times and 2.2times of that of（Ti Cr Mn Co Ni）3O4 and Ti O2,respectively.After the light stability test,the hydrogen production attenuation rate of the composite was 13.6%,which also showed that the composite had better light stability than Ti O2. |
