Preparation of novel protonated forms of the ion-exchangeable layered perovskite via selective reaching of bismuth oxide sheets and their application to photocatalytic activities

Photocatalytic activities of the protonated forms of ion-exchangeable layered perovskites.We investigated the photocatalytic activities of the Aurivillius phases Bi_2ANaNb_3O_&lt；12&gt；(A=Ca or Sr，Bi_2CaNaTa_3O_&lt；12&gt；and the protonated forms of ion-exchangeable layered perovskite prepared from these Aurivillius phases via selective aching of bismuth oxets by acetment。Photocatalytic activities were estimated based on H_2evolution behavior from aqueous ethanol solutions(containing20%ethanol)under UV irradiation.Aurivillius phases showed no activities for H_2evolution，while the protonated forms exhibited the photocatalytic activities。UV-Vis diffuse reflectancee spectra indicated that selective leaching of bismuth oxide sheets led to the change in electric structure.XRD patterns of the protonated forms after H_2evolution showed the increase in the interlayer distance，indicating the effective use of the interlayer space during H_2evolution.Therefore，the difference i…More n the photocatalytic activity behavior between the Aurivillius phases and the protonated forms is attributable to the change in the position of the bottom of the conduction bands and/or the increases in surface area caused by the selective leaching of bismuth oxide sheets.Preparation of novel double-layered tungstic acid.We conducted acid treatment of an Aurivillius phase，Bi_2W2O_9，whose ose-layered tungstic acid.We conducted acid treatment of an Aurivillius phase，Bi_2W2O_9，whose-layered tungstic acid.We conducted acid。XRD，ICP and TG analyses as well as TEM observation showed the selective leaching of the bismuth oxide sheets，indicating the formation of the novel tungstic acid，H_2W_2O_7·nH_2O，which could potentially exhibit the photocatalytic activities.Reaction of the protonated forms of layered perovskite and alcohols.Since the n-alcohol is generally used as a sacrificial reagent for photocatalytic H2O.The reaction of HCa_2Nb_2O_&lt；10&gt；·xH_2O with n-alcohols led to the formation of alkoxy-derivatives of HCa_2Nb_2O_&lt；10&gt；·xH_2O.To achieve high photocatalytic activities，we explored the new pillaring method using organic derivatives of layered perovskities.When we conducted the reaction of CH_2=CH(CH_2)_nO-derivatives(n=3，8)of HLaNb_2O_7·xH_2O with hydrochlorosilanes and oligosiloxanes，XRD，IR and NMR analyses showed the occurrence of hydrosilylation in the interlayer space，indicating that hydrosily lation is utilizable for pillaring.Less：Less

Photocatalytic activities of the protonated forms of ion-exchangeable layered perovskites.We investigated the photocatalytic activities of the Aurivillius phases Bi_2ANaNb_3O_<12> (A=Ca or Sr,Bi_2CaNaTa_3O_<12> and the protonated forms of ion-exchangeable layered perovskite prepared from these Aurivillius phases via selective leaching of bismuth oxide sheets by acid treatment. Photocatalytic activities were estimated based on H_2 evolution behavior from aqueous ethanol solutions (containing 20% ethanol) under UV irradiation. Aurivillius phases showed no activities for H_2 evolution, while the protonated forms exhibited the photocatalytic activities. UV-Vis diffuse reflectancee spectra indicated that selective leaching of bismuth oxide sheets led to the change in electric structure. XRD patterns of the protonated forms after H_2 evolution showed the increase in the interlayer distance, indicating the effective use of the interlayer space during H_2 evolution. Therefore, the difference i … More n the photocatalytic activity behavior between the Aurivillius phases and the protonated forms is attributable to the change in the position of the bottom of the conduction bands and/or the increases in surface area caused by the selective leaching of bismuth oxide sheets.Preparation of novel double-layered tungstic acid.We conducted acid treatment of an Aurivillius phase, Bi_2W_2O_9, whose structure was similar to that of ion-exchangeable layered perovskite. XRD,ICP and TG analyses as well as TEM observation showed the selective leaching of the bismuth oxide sheets, indicating the formation of the novel tungstic acid, H_2W_2O_7・nH_2O, which could potentially exhibit the photocatalytic activities.Reaction of the protonated forms of layered perovskite and alcohols.Since the n-alcohol is generally used as a sacrificial reagent for photocatalytic H_2 evolution from water, we investigated the interaction between the protonated forms of ion-exchangeable layered perovskite HCa_2Nb_2O_<10>・xH_2O and n-alcohol. The reaction of HCa_2Nb_2O_<10>・xH_2O with n-alcohols led to the formation of alkoxy-derivatives of HCa_2Nb_2O_<10>・xH_2O.To achieve high photocatalytic activities, we explored the new pillaring method using organic derivatives of layered perovskite. When we conducted the reaction of CH_2=CH(CH_2)_nO- derivatives (n=3,8) of HLaNb_2O_7・xH_2O with hydrochlorosilanes and oligosiloxanes, XRD,IR and NMR analyses showed the occurrence of hydrosilylation in the interlayer space, indicating that hydrosily lation is utilizable for pillaring. Less