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Akihiko Kudo - One of the best experts on this subject based on the ideXlab platform.
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water splitting and co2 reduction under visible light irradiation using z scheme systems consisting of metal sulfides coox loaded bivo4 and a reduced graphene oxide electron mediator
Journal of the American Chemical Society, 2016Co-Authors: Akihide Iwase, Rose Amal, Yun Hau Ng, Shunya Yoshino, Tomoaki Takayama, Akihiko KudoAbstract:Metal sulfides are highly active Photocatalysts for water reduction to form H2 under visible light irradiation, whereas they are unfavorable for water oxidation to form O2 because of severe self-photooxidation (i.e., photocorrosion). Construction of a Z-scheme system is a useful strategy to split water into H2 and O2 using such photocorrosive metal sulfides because the photogenerated holes in metal sulfides are efficiently transported away. Here, we demonstrate powdered Z-schematic water splitting under visible light and simulated sunlight irradiation by combining metal sulfides as an H2-evolving Photocatalyst, reduced graphene oxide (RGO) as an electron mediator, and a visible-light-driven BiVO4 as an O2-evolving Photocatalyst. This Z-schematic Photocatalyst composite is also active in CO2 reduction using water as the sole electron donor under visible light.
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Z-schematic water splitting into H2 and O2 using metal sulfide as a hydrogen-evolving Photocatalyst and reduced graphene oxide as a solid-state electron mediator
Journal of the American Chemical Society, 2015Co-Authors: Katsuya Iwashina, Akihide Iwase, Rose Amal, Yun Hau Ng, Akihiko KudoAbstract:Z-schematic water splitting was successfully demonstrated using metal sulfide Photocatalysts that were usually unsuitable for water splitting as single particulate Photocatalysts due to photocorrosion. When metal sulfide Photocatalysts with a p-type semiconductor character as a H2-evolving Photocatalyst were combined with reduced graphene oxide-TiO2 composite as an O2-evolving Photocatalyst, water splitting into H2 and O2 in a stoichiometric amount proceeded. In this system, photogenerated electrons in the TiO2 with an n-type semiconductor character transferred to the metal sulfide through a reduced graphene oxide to achieve water splitting. Moreover, this system was active for solar water splitting.
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synthesis of highly active rhodium doped srtio3 powders in z scheme systems for visible light driven photocatalytic overall water splitting
Journal of Materials Chemistry, 2013Co-Authors: Hideki Kato, Yasuyoshi Sasaki, Nana Shirakura, Akihiko KudoAbstract:Two-step excitation photocatalytic systems called Z-scheme systems are attractive to achieve overall water splitting under visible light irradiation. The low activity of SrTiO3:Rh as a H2-evolving Photocatalyst suppresses the overall efficiency of the Z-scheme system composed of SrTiO3:Rh modified with a Pt or Ru cocatalyst, BiVO4, and an Fe3+/Fe2+ electron mediator. In this study, improvement of efficiency for water splitting over the Z-scheme system has been achieved through the preparation of highly efficient SrTiO3:Rh Photocatalysts by hydrothermal and polymerizable complex methods. It has also been revealed that excess amounts of Sr are necessary to obtain highly active SrTiO3:Rh Photocatalysts. Apparent quantum yields of the Z-scheme systems were improved from 0.4% to 3.9–4.2% at 420 nm when SrTiO3:Rh prepared by HT and PC methods was used as a H2-evolving Photocatalyst instead of that prepared by a solid state reaction. The efficiency of the improved Z-scheme system for solar energy conversion was determined to be 0.1%.
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co bpy 3 3 2 and co phen 3 3 2 electron mediators for overall water splitting under sunlight irradiation using z scheme Photocatalyst system
Journal of the American Chemical Society, 2013Co-Authors: Yasuyoshi Sasaki, Hideki Kato, Akihiko KudoAbstract:[Co(bpy)3]3+/2+ and [Co(phen)3]3+/2+ redox couples were revealed to play as electron mediators for Z-scheme Photocatalyst systems composed of Ru/SrTiO3:Rh and BiVO4 powders for overall water splitting under visible light irradiation. These electron mediators were effective for only the combination of SrTiO3:Rh with BiVO4. They did not work when nondoped SrTiO3 and TiO2 of H2-evolving Photocatalysts and WO3 of O2-evolving Photocatalysts were employed. These results indicated that the affinity between Photocatalysts and the Co-complex electron mediators was important. The photocatalytic activity depended on pH. Neutral pH conditions gave the highest activity for overall water splitting. Overall water splitting by the present system steadily proceeded for a long time. The Z-scheme Photocatalyst system was also confirmed to split water under sunlight irradiation at the rates depending on weather. Moreover, overall water splitting by the Z-scheme Photocatalyst system with the Co-complex electron mediator using...
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photocatalytic reduction of carbon dioxide over ag cocatalyst loaded ala4ti4o15 a ca sr and ba using water as a reducing reagent
Journal of the American Chemical Society, 2011Co-Authors: Kosuke Iizuka, Yugo Miseki, Tomoaki Wato, Kenji Saito, Akihiko KudoAbstract:Ag cocatalyst-loaded ALa4Ti4O15 (A = Ca, Sr, and Ba) Photocatalysts with 3.79–3.85 eV of band gaps and layered perovskite structures showed activities for CO2 reduction to form CO and HCOOH by bubbling CO2 gas into the aqueous suspension of the Photocatalyst powder without any sacrificial reagents. Ag cocatalyst-loaded BaLa4Ti4O15 was the most active Photocatalyst. A liquid-phase chemical reduction method was better than impregnation and in situ photodeposition methods for the loading of the Ag cocatalyst. The Ag cocatalyst prepared by the liquid-phase chemical reduction method was loaded as fine particles with the size smaller than 10 nm on the edge of the BaLa4Ti4O15 Photocatalyst powder with a plate shape during the CO2 reduction. CO was the main reduction product rather than H2 even in an aqueous medium on the optimized Ag/BaLa4Ti4O15 Photocatalyst. Evolution of O2 in a stoichiometric ratio (H2+CO:O2 = 2:1 in a molar ratio) indicated that water was consumed as a reducing reagent (an electron donor) fo...
Kazuhiko Maeda - One of the best experts on this subject based on the ideXlab platform.
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photocatalytic water splitting using semiconductor particles history and recent developments
Journal of Photochemistry and Photobiology C-photochemistry Reviews, 2011Co-Authors: Kazuhiko MaedaAbstract:Abstract Overall water splitting to produce H 2 and O 2 over a semiconductor Photocatalyst using solar energy is a promising process for the large-scale production of clean, recyclable H 2 . Numerous attempts have been made to develop Photocatalysts that function under visible-light irradiation to efficiently utilize solar energy. In general, overall water splitting over a Photocatalyst particle can be achieved by modifying the Photocatalyst with a suitable cocatalyst to provide an active redox site. Therefore, the development of active photocatalytic materials has relied on both Photocatalysts and cocatalysts. This review article describes the historical development of water-splitting Photocatalysts.
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photocatalytic water splitting recent progress and future challenges
Journal of Physical Chemistry Letters, 2010Co-Authors: Kazuhiko Maeda, Kazunari DomenAbstract:Water splitting to form hydrogen and oxygen using solar energy in the presence of semiconductor Photocatalysts has long been studied as a potential means of clean, large-scale fuel production. In general, overall water splitting can be achieved when a Photocatalyst is modified with a suitable cocatalyst. It is therefore important to develop both Photocatalysts and cocatalysts. In the past five years, there has been significant progress in water splitting photocatalysis, especially in the development of cocatalysts and related physical and materials chemistry. This work describes the state of the art and future challenges in photocatalytic water splitting, with a focus on the recent progress of our own research.
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efficient nonsacrificial water splitting through two step photoexcitation by visible light using a modified oxynitride as a hydrogen evolution Photocatalyst
Journal of the American Chemical Society, 2010Co-Authors: Kazuhiko Maeda, Masanobu Higashi, Ryu Abe, Kazunari DomeAbstract:A two-step photocatalytic water splitting (Z-scheme) system consisting of a modified ZrO2/TaON species (H2 evolution Photocatalyst), an O2 evolution Photocatalyst, and a reversible donor/acceptor pair (i.e., redox mediator) was investigated. Among the O2 evolution Photocatalysts and redox mediators examined, Pt-loaded WO3 (Pt/WO3) and the IO3−/I− pair were respectively found to be the most active components. Combining these two components with Pt-loaded ZrO2/TaON achieved stoichiometric water splitting into H2 and O2 under visible light, achieving an apparent quantum yield of 6.3% under irradiation by 420.5 nm monochromatic light under optimal conditions, 6 times greater than the yield achieved using a TaON analogue. To the best of our knowledge, this is the highest reported value to date for a nonsacrificial visible-light-driven water splitting system. The high activity of this system is due to the efficient reaction of electron donors (I− ions) and acceptors (IO3− ions) on the Pt/ZrO2/TaON and Pt/WO3 ph...
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solid solution of gan and zno as a stable Photocatalyst for overall water splitting under visible light
Chemistry of Materials, 2010Co-Authors: Kazuhiko Maeda, Kazunari DomeAbstract:Large-scale hydrogen production from water using only solar energy is an ultimate goal for the supply of clean, recyclable energy, and several reactions and schemes have been proposed. Overall water splitting using a particulate Photocatalyst is one attractive solution with a wide range of applications. A number of Photocatalysts have been proposed, and some have achieved high quantum efficiencies. Unfortunately, most of these Photocatalysts consist of metal oxides and work only in the ultraviolet (UV) region. To effectively utilize solar energy, it is necessary to develop a material that will function under visible light. This paper reviews the recent development of such a Photocatalyst, specifically focusing on efforts by the authors’ group to prepare a solid solution of GaN and ZnO. This new material is capable of splitting water into hydrogen and oxygen under visible light (λ > 400 nm) with good reproducibility.
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gan zno solid solution as a Photocatalyst for visible light driven overall water splitting
Journal of the American Chemical Society, 2005Co-Authors: Kazuhiko Maeda, Tsuyoshi Takata, Michikazu Hara, Nobuo Saito, Yasunobu Inoue, Hisayoshi Kobayashi, Kazunari DomenAbstract:Photocatalytic overall water splitting has been studied extensively from the viewpoint of solar energy conversion. Despite numerous attempts, none have yielded satisfactory results for the development of Photocatalysts, which work under visible light irradiation to efficiently utilize solar energy. We report here the first example of visible-light-driven overall water splitting on a novel oxynitride Photocatalyst, a solid solution of GaN and ZnO with a band gap of 2.58−2.76 eV, modified with RuO2 nanoparticles. In contrast to the conventional non-oxide Photocatalysts, such as CdS, the solid solution is stable during the overall water splitting reaction. This is the first example of achieving overall water splitting by a Photocatalyst with a band gap in the visible light region, which opens the possibility of new non-oxide-type Photocatalysts for energy conversion.
Kazunari Domen - One of the best experts on this subject based on the ideXlab platform.
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mutually dependent kinetics and energetics of Photocatalyst co catalyst two redox liquid junctions
Energy and Environmental Science, 2020Co-Authors: Rito Yanagi, Kazunari Domen, Qian Wang, Xin Shen, Jason A Rohr, Takashi Hisatomi, Shu HuAbstract:Water-splitting by Photocatalyst particles has attracted much attention recently for its potential to produce renewable H2 at scale. However, the correlation between the energetics at Photocatalyst/co-catalyst/water interfaces and their interfacial charge-transfer kinetics is still elusive, especially when the energetics are expected to vary spatially along the liquid-junction interface. First, we derived a kinetic model for Photocatalyst particles in contact with two-redox potentials, H+/H2 and O2/H2O, i.e., a semiconductor/two-redox liquid junction. We adopted the principle of detailed balance proven for one-redox liquid junctions and extended this principle to a locally out-of-equilibrium electrolyte containing multiple redox potentials, the condition typical for Photocatalysts. To validate the model, we established a characterization framework to simulate Photocatalyst operation by using photoelectrodes. The open-circuit conditions mimicked operating Photocatalyst surfaces; and the (quasi-) Fermi levels, probed by ohmic back contacts, indicated charge-separation efficiency. Quantitative data fitting further validated the two-redox kinetic model. These characterizations correlated local energetics with multi-electron charge-transfer kinetics, which exhibit tuneable branching ratios controlled by H2-and-O2 gas-mixture compositions and co-catalyst selectivity. Unlike the conventional photoelectrode/electrolyte interfaces, SrTiO3 model particles decorated with Pt co-catalysts were found to bear liquid-junction interfaces of spatially varying energetics with designated reductive and oxidative sites. It is shown that, uniquely for Photocatalysts, the local kinetic-controlled energetics vary spatially across Photocatalyst/co-catalyst/water interfaces of individual particles, and affect charge-separation efficiency sensitively. The mutually dependent behaviour between local kinetics and spatially varying energetics were confirmed for two practical photocatalytic systems, Al-doped SrTiO3 and Ta3N5. This study exemplified and elucidated the design principles for developing efficient Photocatalysts.
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photocatalytic water splitting recent progress and future challenges
Journal of Physical Chemistry Letters, 2010Co-Authors: Kazuhiko Maeda, Kazunari DomenAbstract:Water splitting to form hydrogen and oxygen using solar energy in the presence of semiconductor Photocatalysts has long been studied as a potential means of clean, large-scale fuel production. In general, overall water splitting can be achieved when a Photocatalyst is modified with a suitable cocatalyst. It is therefore important to develop both Photocatalysts and cocatalysts. In the past five years, there has been significant progress in water splitting photocatalysis, especially in the development of cocatalysts and related physical and materials chemistry. This work describes the state of the art and future challenges in photocatalytic water splitting, with a focus on the recent progress of our own research.
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gan zno solid solution as a Photocatalyst for visible light driven overall water splitting
Journal of the American Chemical Society, 2005Co-Authors: Kazuhiko Maeda, Tsuyoshi Takata, Michikazu Hara, Nobuo Saito, Yasunobu Inoue, Hisayoshi Kobayashi, Kazunari DomenAbstract:Photocatalytic overall water splitting has been studied extensively from the viewpoint of solar energy conversion. Despite numerous attempts, none have yielded satisfactory results for the development of Photocatalysts, which work under visible light irradiation to efficiently utilize solar energy. We report here the first example of visible-light-driven overall water splitting on a novel oxynitride Photocatalyst, a solid solution of GaN and ZnO with a band gap of 2.58−2.76 eV, modified with RuO2 nanoparticles. In contrast to the conventional non-oxide Photocatalysts, such as CdS, the solid solution is stable during the overall water splitting reaction. This is the first example of achieving overall water splitting by a Photocatalyst with a band gap in the visible light region, which opens the possibility of new non-oxide-type Photocatalysts for energy conversion.
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a highly active Photocatalyst for overall water splitting with a hydrated layered perovskite structure
Journal of Photochemistry and Photobiology A-chemistry, 1997Co-Authors: T Takata, Michikazu Hara, Kiyoaki Shinohara, Akira Tanaka, Junko N Kondo, Kazunari DomenAbstract:Photocatalytic decomposition of H2O into H2 and O2 over a novel Photocatalyst, K2La2Ti3O10, was accomplished. K2La2Ti3O10, a layered perovskite-type compound with a hydrated interlayer space, exhibited a high activity for overall water splitting with Ni-loading. The highest activity was obtained over Ni(3.0 wt%)–K2La2Ti3O10 when the reaction was carried out in aqueous KOH solution (0.1 M, pH=12.8). By comparison with other Ni-loaded Photocatalysts reported previously, the reaction mechanism of Ni–K2La2Ti3O10 was discussed. © 1997 Elsevier Science S.A.
Kazunari Dome - One of the best experts on this subject based on the ideXlab platform.
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efficient nonsacrificial water splitting through two step photoexcitation by visible light using a modified oxynitride as a hydrogen evolution Photocatalyst
Journal of the American Chemical Society, 2010Co-Authors: Kazuhiko Maeda, Masanobu Higashi, Ryu Abe, Kazunari DomeAbstract:A two-step photocatalytic water splitting (Z-scheme) system consisting of a modified ZrO2/TaON species (H2 evolution Photocatalyst), an O2 evolution Photocatalyst, and a reversible donor/acceptor pair (i.e., redox mediator) was investigated. Among the O2 evolution Photocatalysts and redox mediators examined, Pt-loaded WO3 (Pt/WO3) and the IO3−/I− pair were respectively found to be the most active components. Combining these two components with Pt-loaded ZrO2/TaON achieved stoichiometric water splitting into H2 and O2 under visible light, achieving an apparent quantum yield of 6.3% under irradiation by 420.5 nm monochromatic light under optimal conditions, 6 times greater than the yield achieved using a TaON analogue. To the best of our knowledge, this is the highest reported value to date for a nonsacrificial visible-light-driven water splitting system. The high activity of this system is due to the efficient reaction of electron donors (I− ions) and acceptors (IO3− ions) on the Pt/ZrO2/TaON and Pt/WO3 ph...
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solid solution of gan and zno as a stable Photocatalyst for overall water splitting under visible light
Chemistry of Materials, 2010Co-Authors: Kazuhiko Maeda, Kazunari DomeAbstract:Large-scale hydrogen production from water using only solar energy is an ultimate goal for the supply of clean, recyclable energy, and several reactions and schemes have been proposed. Overall water splitting using a particulate Photocatalyst is one attractive solution with a wide range of applications. A number of Photocatalysts have been proposed, and some have achieved high quantum efficiencies. Unfortunately, most of these Photocatalysts consist of metal oxides and work only in the ultraviolet (UV) region. To effectively utilize solar energy, it is necessary to develop a material that will function under visible light. This paper reviews the recent development of such a Photocatalyst, specifically focusing on efforts by the authors’ group to prepare a solid solution of GaN and ZnO. This new material is capable of splitting water into hydrogen and oxygen under visible light (λ > 400 nm) with good reproducibility.
Jiaguo Yu - One of the best experts on this subject based on the ideXlab platform.
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cu2 oh 2co3 clusters novel noble metal free cocatalysts for efficient photocatalytic hydrogen production from water splitting
Applied Catalysis B-environmental, 2017Co-Authors: Zhikang He, Jiaguo Yu, Junwei Fu, Bei ChengAbstract:Abstract Photocatalytic hydrogen evolution is a potential route for converting inexhaustible solar energy into available clean chemical energy. Herein, highly efficient and stable Cu2(OH)2CO3/TiO2 Photocatalysts for hydrogen generation are prepared by incorporating Cu2(OH)2CO3 clusters onto the surface of TiO2 through a facile precipitation method. The obtained Cu2(OH)2CO3/TiO2 Photocatalyst with optimal Cu2(OH)2CO3 content of 0.5 mol% shows an outstanding photocatalytic H2-production rate of 6713 μmol h−1 g−1 (with apparent quantum efficiency of 15.4% at 365 nm), which is comparable to the excellent Pt/TiO2 Photocatalyst and more efficient than other copper specie modified TiO2 Photocatalyst. The formation of Cu2(OH)2CO3/Cu+/Cu0 clusters essentially contribute to the enhanced H2-production activity by reducing the over-potential of water reduction and promoting the transfer of photogenerated electrons from the conduction band of TiO2 to the Cu2(OH)2CO3/Cu+/Cu0 clusters. A high stability of the Cu2(OH)2CO3/TiO2 Photocatalyst is achieved due to the re-oxidation process of Cu+/Cu0 to Cu2(OH)2CO3 and structure confinement of Cu2(OH)2CO3 clusters in the mesopores of TiO2. This work brings in new insight in developing low-cost noble-metal-free photocatalytic system for solar-to-fuel conversion.
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ultra thin nanosheet assemblies of graphitic carbon nitride for enhanced photocatalytic co2 reduction
Journal of Materials Chemistry, 2017Co-Authors: Jiaguo Yu, Mietek JaroniecAbstract:A two-dimensional layered polymeric Photocatalyst, graphitic carbon nitride (g-C3N4), is becoming the rising star in the field of solar-to-fuel conversion. However, the performance of commonly prepared g-C3N4 is usually very weak because of the high recombination rate of photogenerated charge carriers and a small amount of surface active sites. Here we demonstrate simultaneous texture modification and surface functionalization of g-C3N4via a stepwise NH3-mediated thermal exfoliation approach. The resulting g-C3N4 Photocatalyst possesses a hierarchical structure obtained by the assembly of amine-functionalized ultrathin nanosheets and thus exhibits remarkably enhanced light harvesting, a high redox ability of charge carriers, increased CO2 adsorption and a larger amount of surface active sites, as well as improved charge carrier transfer and separation. Therefore the aforementioned hierarchical g-C3N4 consisting of amine-functionalized ultra-thin nanosheets shows much better performance for photocatalytic CO2 reduction than unmodified conventional g-C3N4 Photocatalysts.
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enhanced photoinduced stability and photocatalytic activity of cds by dual amorphous cocatalysts synergistic effect of ti iv hole cocatalyst and ni ii electron cocatalyst
Journal of Physical Chemistry C, 2016Co-Authors: Huogen Yu, Xiao Huang, Ping Wang, Jiaguo YuAbstract:CdS is one of the most well-known and important visible-light photocatalytic materials for water splitting to produce hydrogen energy. Owing to its serious photocorrosion property (poor photoinduced stability), however, CdS Photocatalyst can unavoidably be oxidized to form S0 by its photogenerated holes, causing an obviously decreased photocatalytic performance. In this study, to improve the photoinduced stability of CdS Photocatalyst, amorphous TiO2 (referred to as Ti(IV)) as a hole cocatalyst was successfully loaded on the CdS surface to prepare Ti(IV)/CdS Photocatalysts. It was found that the resultant Ti(IV)/CdS Photocatalyst exhibited an obviously enhanced photocatalytic stability, namely, its deactivation rate clearly decreased from 37.9% to 13.5% after five cycles of photocatalytic reactions. However, its corresponding photocatalytic activity only showed a very limited increase (ca. 37.4%) compared with the naked CdS. To further improve its photocatalytic performance, the amorphous Ni(II) as an ele...
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enhanced photocatalytic performance of direct z scheme g c3n4 tio2 Photocatalysts for the decomposition of formaldehyde in air
Physical Chemistry Chemical Physics, 2013Co-Authors: Jiaguo Yu, Shuhan Wang, Wei XiaoAbstract:Formaldehyde (HCHO) is a major indoor pollutant and long-term exposure to HCHO may cause health problems such as nasal tumors and skin irritation. Photocatalytic oxidation is considered as the most promising strategy for the decomposition of HCHO. Herein, for the first time, a direct g-C3N4–TiO2 Z-scheme Photocatalyst without an electron mediator was prepared by a facile calcination route utilizing affordable P25 and urea as the feedstocks. Photocatalytic activities of the as-prepared samples were evaluated by the photocatalytic oxidation decomposition of HCHO in air. It was shown that the photocatalytic activity of the prepared Z-scheme Photocatalysts was highly dependent on the g-C3N4 content. At the optimal g-C3N4 content (sample U100 in this study), the apparent reaction rate constant was 7.36 × 10−2 min−1 for HCHO decomposition, which exceeded that of pure P25 (3.53 × 10−2 min−1) by a factor of 2.1. The enhanced photocatalytic activity could be ascribed to the formation of a g-C3N4–TiO2 Z-scheme Photocatalyst, which results in the efficient space separation of photo-induced charge carriers. Considering the ease of the preparation method, this work will provide new insights into the design of high-performance Z-scheme Photocatalysts for indoor air purification.
