Study on photocatalyst for hydrogen production by photolysis of water

Tantalates atao3 (a = li, k) and a2srta2o7 nh2o (a = h, k, rb) have similar crystal structures, but they all share the common features of octahedral TaO6. Kato H. et al. studied the photocatalytic activity of tantalate series LiTaO _ 3, Natao _ 3 and KTaO3 _ 3. It was found that both the unloaded LiTaO _ 3 and Natao _ 3 achieved good photocatalytic effect under ultraviolet irradiation, while the activity of NiO-loaded Natao _ 3 in decomposing water was significantly improved under ultraviolet irradiation, and the quantum efficiency reached 28%. However, when LiTaO3 _ 3 and KTaO3 _ 3 are loaded with NiO, their photocatalytic activity decreases, which can be explained by the conduction band position of tantalate. The conduction band position of NataO _ 3 is higher than that of NiO, so the photogenerated electrons generated in the conduction band of NataO _ 3 can be easily transferred to the conduction band of NiO, thus enhancing the separation of electrons and holes and improving the photocatalytic activity. The conduction band position of KTaO3 is lower than that of NiO, which can not produce this effect. However, after LiTaO _ 3 was loaded with NiO, Li+ was doped into NiO, which led to the deactivation of NiO catalyst and reduced the photocatalytic activity of LiTaO _ 3. As soon as Kudo discovered alkali metals,

Alkaline earth metal tantalate, as a catalytic material for ultraviolet light to decompose water, shows high activity under no-load condition. After doping La, the activity of NiO/NaTaO3 is the highest. Ikeda et al. synthesized Ca2Ta2O7, Na2Ta2O6 and K2Ta2O6 by hydrothermal method, and put NiO-loaded Ca2Ta2O7 and pure Ca2Ta2O7 into 0. 1 mmol dm3 NaOH solution respectively. By the end of the reaction, it was found that NiO/Ca2Ta2O7 saved 6 hours compared with pure Ca2Ta2O7, and it was analyzed by XRD before and after the reaction. Comparing NiO/Na2Ta2O6, NiO/ K2Ta2O6 and NiO/ Ca2Ta2O7, it is found that NiO/ Na2Ta2O6 and NiO/K2Ta2O6 have stronger catalytic ability than NiO/ Ca2Ta2O7, which may be because the energy gap of Ca2Ta2O7 is narrower than that of Na2Ta2O6 and K2Ta2O6, or because of Ca2Ta2O7. Yoshioka K. et al. studied the catalytic activities of SrTa2O6, SRT A2O9, Sr5Ta4O 15, and Sr2Ta2O7 for water, and found that their catalytic activities were Sr2Ta2O7 >. Sr 5 ta 4 o 15 & gt； Srta 2O 6 & GTSR 4 T 2O 9, which is mainly due to their different crystal structures. ZnSeS compounds can form solid solutions with narrow energy gaps. Xu Yunbo et al. prepared ZnSeS photocatalyst doped with copper and indium by chemical precipitation method. It is found that when the molar fraction of Cu and In in ZnSeS is 2%, its light absorption performance is the best, and the maximum absorption edge shifts to 700nm. Under ultraviolet irradiation, the quantum efficiency of photocatalytic decomposition of hydrogen in water reaches 4.83%. The catalyst has good thermal stability and light stability, and its hydrogen production performance does not decay after reaction100h. Cubic Znln2S4 has a bandwidth of 2.3eV, visible light response characteristics and good stability, and can be used as photocatalytic materials. Znln2S4 with cubic spinel structure with high specific surface area was prepared by hydrothermal synthesis method. After loading 2%Pt, the maximum hydrogen production rate can reach 213&in 0.43 mol/l LNA2S-0.5 mol/l Na2SO3 solution. Microscopic; Mol/h Kudo A. et al. found that AgInZn7S9 can be excited by visible light to produce hydrogen from an aqueous solution containing SO32- or S2- without adding Pt cocatalyst; The catalytic activity is better after loading Pt, and the maximum hydrogen production rate can reach 970 & micro；; Molar/hour. Yang prepared Zn0.957Cu0.043S and Zn0.999Ni0.00 1S, in which

Zn0.957Cu0.043S comes from K2SO3 and Na2S under the irradiation of visible light.

H2 is released from aqueous solution, and Zn0.999Ni0.00 1S can also release H2 from K2SO3 and Na2S aqueous solution under N2 flow and 770K K heat treatment ... Wen et al. prepared C60 aqueous solution, mixed with Zn0.999Ni0.00 1S, and followed the reaction by gas chromatography. It is found that the amount of hydrogen released is more than four times that without C60. Because C60 is a strongly electronegative substance, when it is mixed with Zn0.999Ni0.00 1S, it can be used as a shallow potential trap for electrons, which effectively inhibits the recombination of electrons and holes, thus promoting the reaction.