A dye-sensitized photocatalyst combining Pt-loaded TiO_(2) and Ru(Ⅱ)tris-diimine sensitizer(RuP)was constructed and its activity for photochemical hydrogen evolution was compared with that of Pt-intercalated HCa_(2)N...A dye-sensitized photocatalyst combining Pt-loaded TiO_(2) and Ru(Ⅱ)tris-diimine sensitizer(RuP)was constructed and its activity for photochemical hydrogen evolution was compared with that of Pt-intercalated HCa_(2)Nb_(3)O_(10) nanosheets.When the sacrificial donor ethylenediaminetetraacetic acid(EDTA)disodium salt dihydrate was used,RuP/Pt/TiO_(2) showed higher activity than RuP/Pt/HCa_(2)Nb_(3)O_(10).In contrast,when NaI(a reversible electron donor)was used,RuP/Pt/TiO_(2) showed little activity due to back electron transfer to the electron acceptor(I_(3)-),which was gener-ated as the oxidation product of I-.By modification with anionic polymers(sodium poly(styrenesulfonate)or sodium polymethacrylate)that could inhibit the scavenging of conduction band electrons by I_(3)-,the H_(2) production activity from aqueous NaI was improved,but it did not exceed that of RuP/Pt/HCa_(2)Nb_(3)O_(10).Transient absorption measurements showed that the rate of semiconductor-to-dye back electron transfer was slower in the case of TiO_(2) than HCa_(2)Nb_(3)O_(10),but the electron transfer reaction to I3-was much faster.These results indicate that Pt/TiO_(2) is useful for reactions with sacrificial reductants(e.g.,EDTA),where the back electron transfer reaction to the more reducible product can be neglected.However,more careful design of the catalyst will be nec-essary when a reversible electron donor is employed.展开更多
Pt‐loaded graphitic carbon nitride(g‐C_(3)N_(4))is known to be a good photocatalyst for H_(2) evolution under visible light.In most cases,however,sacrificial electron donors such as triethanolamine are required for ...Pt‐loaded graphitic carbon nitride(g‐C_(3)N_(4))is known to be a good photocatalyst for H_(2) evolution under visible light.In most cases,however,sacrificial electron donors such as triethanolamine are required for the water‐splitting operation,and nonsacrificial H_(2) evolution by g‐C_(3)N_(4) remains a challenge.In this work,we investigated the photocatalytic activities of carbon nitride nanosheet(NS‐C_(3)N_(4)),which was prepared by thermal treatment of urea,for nonsacrificial H_(2) evolution using reversible electron donors under visible light(λ>400 nm).Whereas Pt‐loaded NS‐C_(3)N_(4) did not produce H_(2) from aqueous solutions containing I−,Fe^(2+),or[Fe(CN)_(6)]^(4−),modification of the Pt/NS‐C_(3)N_(4) photocatalyst with CrO_(x) led to observable H_(2) evolution.Transmission electron microscopy observations and energy‐dispersive X‐ray spectroscopic analysis suggested that a Pt‐core/CrO_(x)‐shell structure was formed on the NS‐C_(3)N_(4).The CrO_(x)/Pt/NS‐C_(3)N_(4) served as a H_(2)‐evolution photocatalyst for visible‐light‐driven Z‐scheme overall water splitting,in combination with a modified WO_(3) photocatalyst,in the presence of a[Fe(CN)_(6)]^(3−/4−)redox mediator.展开更多
文摘A dye-sensitized photocatalyst combining Pt-loaded TiO_(2) and Ru(Ⅱ)tris-diimine sensitizer(RuP)was constructed and its activity for photochemical hydrogen evolution was compared with that of Pt-intercalated HCa_(2)Nb_(3)O_(10) nanosheets.When the sacrificial donor ethylenediaminetetraacetic acid(EDTA)disodium salt dihydrate was used,RuP/Pt/TiO_(2) showed higher activity than RuP/Pt/HCa_(2)Nb_(3)O_(10).In contrast,when NaI(a reversible electron donor)was used,RuP/Pt/TiO_(2) showed little activity due to back electron transfer to the electron acceptor(I_(3)-),which was gener-ated as the oxidation product of I-.By modification with anionic polymers(sodium poly(styrenesulfonate)or sodium polymethacrylate)that could inhibit the scavenging of conduction band electrons by I_(3)-,the H_(2) production activity from aqueous NaI was improved,but it did not exceed that of RuP/Pt/HCa_(2)Nb_(3)O_(10).Transient absorption measurements showed that the rate of semiconductor-to-dye back electron transfer was slower in the case of TiO_(2) than HCa_(2)Nb_(3)O_(10),but the electron transfer reaction to I3-was much faster.These results indicate that Pt/TiO_(2) is useful for reactions with sacrificial reductants(e.g.,EDTA),where the back electron transfer reaction to the more reducible product can be neglected.However,more careful design of the catalyst will be nec-essary when a reversible electron donor is employed.
基金supported by the Grants-in-Aid for Scientific Research on the Innovative Area “Mixed Anion” (Project JP16H06441) by the Japan Society for the Promotion of Science (JSPS), and the Japan Association for Chemical Innovation
文摘Pt‐loaded graphitic carbon nitride(g‐C_(3)N_(4))is known to be a good photocatalyst for H_(2) evolution under visible light.In most cases,however,sacrificial electron donors such as triethanolamine are required for the water‐splitting operation,and nonsacrificial H_(2) evolution by g‐C_(3)N_(4) remains a challenge.In this work,we investigated the photocatalytic activities of carbon nitride nanosheet(NS‐C_(3)N_(4)),which was prepared by thermal treatment of urea,for nonsacrificial H_(2) evolution using reversible electron donors under visible light(λ>400 nm).Whereas Pt‐loaded NS‐C_(3)N_(4) did not produce H_(2) from aqueous solutions containing I−,Fe^(2+),or[Fe(CN)_(6)]^(4−),modification of the Pt/NS‐C_(3)N_(4) photocatalyst with CrO_(x) led to observable H_(2) evolution.Transmission electron microscopy observations and energy‐dispersive X‐ray spectroscopic analysis suggested that a Pt‐core/CrO_(x)‐shell structure was formed on the NS‐C_(3)N_(4).The CrO_(x)/Pt/NS‐C_(3)N_(4) served as a H_(2)‐evolution photocatalyst for visible‐light‐driven Z‐scheme overall water splitting,in combination with a modified WO_(3) photocatalyst,in the presence of a[Fe(CN)_(6)]^(3−/4−)redox mediator.
