Monolithic Ag-Mt dispersed Z-scheme pCN-TiO2 heterojunction for dynamic photocatalytic H2 evolution using liquid and gas phase photoreactors

Fabricating montmorillonite (Mt) dispersed Ag/pCN-TiO₂ heterojunction for stimulating photocatalytic H₂ evolution using two/three phases photo-reactor systems has been investigated. Using Ag–Mt/pCN–TiO₂ composite in three-phase, H₂ rate of 667 μmolh⁻¹ was obtained, much greater than TiO₂-based samples due to superior charges separation with Ag SPR and Mt mediated effect. Among parameters, 0.15 g catalyst loading at pH 7 gives highest H₂ yield with glycerol sacrificial reagents. More interestingly, liquid system with glycerol gave best H₂ rate while gas-phase with methanol encouraged H₂ productivity. Furthermore, H₂ rate increased to 8230 μmolh⁻¹ using two-phase monolith reactor, 9.01 and 12.34 times greater than two-phase fixed-bed and three-phase slurry systems. Comparatively, highest AQY and SY of 39.85% and 54.86 μmolh⁻¹cm⁻³ were obtained using monolith. This superior efficiency was due to efficient photon-flux consumption, effective mass-transfer and large light-fluxed. These findings would be fruitful for further development for clean hydrogen production through photocatalytic water splitting.     

Electrochemical reduction induced self-doping of oxygen vacancies into Ti–Si–O nanotubes as efficient photoanode for boosted photoelectrochemical water splitting

Self-doping of oxygen vacancies (V_O) states into TiO₂-based nanotubes was an efficient way for improving photoelectrochemical (PEC) water splitting properties. Here we induced oxygen vacancies into Si-doped TiO₂ (Ti–Si–O) nanotubes on Ti–Si alloy via a facile electrochemical surface reduction, and applied it for PEC water splitting. Systematic studies revealed that the self-doped oxygen vacancies not only promoted optical absorption of the doped nanotubes but also enhanced separation-transport processes of the photo-generated charge carriers, and thus resulted in improved PEC water splitting properties. The V_O/Ti–Si–O co-doping system exhibited a higher photocurrent density of 1.63 mA/cm² at 0 V vs. Ag/AgCl. Corresponding solar-to-hydrogen efficiency could reach 0.81%, which was about 5.4 times that of undoped TiO₂. It's believed that elements doping and oxygen vacancies self-doping synergistic strategy employed in this work, may provide theoretical and practical significance for designing and fabricating efficient TiO₂-based nanostructures photoanodes in PEC water splitting for boosted solar-to-hydrogen conversion.     

LED light-induced enhanced photocatalytic hydrogen evolution on Au@TiO2 core–shell modified by nitrogen doping and reduced graphene oxide

This study focused on the large band gap of TiO₂ for its use as a photocatalyst under light emitting diode (LED) light irradiation. The photocatalytic activities of core–shell structured Au@TiO₂ nanoparticles (NPs), nitrogen doped Au@TiO₂ NPs, and Au@TiO₂/rGO nanocomposites (NCs) were investigated under various light intensities and sacrificial reagents. All the materials showed better photocatalytic activity under white LED light irradiation than under blue LED light. The N-doped core–shell structured Au@TiO₂ NPs (Au@N–TiO₂) and Au@TiO₂/rGO NCs showed enhanced photocatalytic activity with an average H₂ evolution rate of 9205 μmol h^?1g^?1 and 9815 μmol h^?1g^?1, respectively. All these materials showed an increasing rate of hydrogen evolution with increasing light intensity and catalyst loading. In addition, methanol was more suitable as a sacrificial reagent than lactic acid. The rate of hydrogen evolution increased with increasing methanol concentration up to 25% in DI water and decreased at higher concentrations. Overall, Au@TiO₂ core–shell-based nanocomposites can be used as an improved photocatalyst in photocatalytic hydrogen production.     

Core-shell hetero-phase reduced Ti–Ni–O nanotubes photoanode with enhanced optical absorption and charge transport for boosted photoelectrochemical water splitting

Bulk-phase doping and surface oxygen-defective engineering of TiO₂-based nanostructures are identified as effective routes for enhanced photoelectrochemical (PEC) water splitting. Here, we reported a reduced Ti–Ni–O nanotubes photoanode with anatase-rutile crystalline-core and oxygen vavancies amorphous-shell for boosted PEC water splitting. The core-shell hetero-phase reduced Ti–Ni–O nanotubes were fabricated through phase-structure modulation by a thermal treatment of anodized Ti–Ni–O nanotubes on Ti–Ni alloy and with one-step electrochemical reduction. Microstructure, optical and PEC measurement results confirmed effective bulk-phase Ni-doping and surface oxygen vacancies self-doping into the reduced mixed-phase Ti–Ni–O nanotubes, which enabled high capability of optical-absorption and simultaneously favored charge separation-transfer for remarkably improved the PEC water splitting. A higher photocurrent density of 1.66 mA/cm² at 0 V vs. Ag/AgCl and solar-to-hydrogen efficiency of 0.79% were achieved for the reduced Ti–Ni–O system, which was 5.35 and 5.27 times that of undoped TiO₂, respectively. This work may shed an insight view on fabricating high-performance Ti-based nano-photoanodes with enhanced light harvesting and carrier kinetics for efficient PEC water splitting, through synergistic strategy of bulk-phase elements doping and surface oxygen vacancies self-doping.     

Enhancing hydrogen evolution of water splitting under solar spectra using Au/TiO2 heterojunction photocatalysts

An effective improvement of hydrogen evolution from water splitting under solar light irradiation was investigated using quantum dots (QDs) compounds loaded onto a Au/TiO₂ photocatalyst. First, Au/TiO₂ was prepared by the deposition-precipitation method, and then sulfide QDs were loaded onto the as-prepared Au/TiO₂ by a hydrothermal method. QDs were loaded onto Au/TiO₂ to enhance the energy capture of visible light and near-infrared light of the solar spectrum. The results indicated that the as-prepared heterojunction photocatalysts absorbed the energy from the range of ultraviolet light to the near-infrared light region and effectively reduced the electron-hole pair recombination during the photocatalytic reaction. Using a hydrothermal temperature of 120 °C, the as-prepared (ZnS–PbS)/Au/TiO₂ photocatalyst had a PbS QDs particle size of 5 nm, exhibited an energy gap of 0.92 eV, and demonstrated the best hydrogen production rate. Additionally, after adding 20 wt % methanol as a sacrificial reagent to photocatalyze for 5 h, the hydrogen production rate reached 5011 μmol g⁻¹ h⁻¹.     

Ti–Fe mixed oxides as photocatalysts in the generation of hydrogen under UV-light irradiation

Ti–Fe mixed oxides were prepared by sol-gel and used as photocatalysts for the generation H₂ from water. The solids were characterized by SEM-EDS, N₂ physisorption, XRD, UV–Vis and XPS spectroscopy. The mixed oxides present larger specific surface areas (83–205 m²/g) than that of pure TiO₂ (64 m²/g). The XRD patterns of the Ti–Fe solids resemble that of anatase titania. The band gap energies of the solids vary from 3.0 to 2.5 eV and are smaller than that of TiO₂ (3.2 eV). The mixed oxides were tested as photocatalysts in the production of hydrogen from water using methanol as a sacrificial agent. In all cases, their catalytic activities were higher than that exhibited by TiO₂ after 10 h of reaction.     

TiO2 nanosheets loaded with Cu: A low-cost efficient photocatalytic system for hydrogen evolution from water

Rutile TiO₂ nanosheets were prepared by a simple solvothermal process, and Cu was loaded on the surface of TiO₂ nanosheets using the in situ photo-deposition method. Meanwhile, photocatalytic H₂ evolution from water over the as-prepared TiO₂ nanosheets loaded with Cu was explored using methanol as a sacrificial reagent. The results indicate that the TiO₂ nanosheets loaded with Cu is an efficient photocatalyst under UV irradiation. During the first 5 h, a rate of H₂ evolution of approximately 22.1 mmol g⁻¹ h⁻¹ was achieved under optimal conditions. Furthermore, for practical purposes, the photocatalytic hydrogen evolution was studied as a function of content of Cu, pH of solution, concentration of methanol and dosage of photocatalyst, respectively. At last, the photocatalytic mechanism was preliminarily discussed.     

Structural properties of CuO/TiO2 nanorod in relation to their catalytic activity for simultaneous hydrogen production under solar light

CuO was introduced into porous TiO₂ nanorod through impregnation method. Before the impregnation step, TiO₂ nanorod was hydrothermally synthesized from TiO₂ powder in aqueous NaOH solution and followed by thermal treatment at 450 °C. The structures and properties of impregnated samples were characterized using various techniques, including XRD, BET, XAS, TEM, and UV-DRS. Their photocatalytic performance on simultaneous hydrogen production from pure water and aqueous methanol solution was also investigated under solar light. It was found that CuO/TiO₂ nanorod possessed a high surface area, good photocatalytic property and excellent hydrogen generation activity. Incorporation of Cu ions into the lattice framework of anatase TiO₂ nanorod enhanced the efficiency in visible region at 438–730 nm. Moreover, the XAS results showed that some Cu ions formed solid solution in the TiO₂ nanorod (Cu_xT_1−xO₂). However, the excessive incorporation of Cu ions did not improve any ability of anatase TiO₂ nanorod for production of hydrogen from pure water splitting. This could be due to the excessive CuO agglomeration at outside-pores which blocked the sensitization of TiO₂ nanorod. Only 1% Cu/TiO₂ nanorod was found to be a remarkable and an efficient photocatalyst for hydrogen production under solar light from both pure water and sacrificial methanol splitting. The highest rate of hydrogen production of 139.03 μmol h⁻¹ g_catalyst⁻¹ was found in sacrificial methanol which was 3.24% higher than in pure water.     

A triptych photocatalyst based on the Co-Integration of Ag nanoparticles and carbo-benzene dye into a TiO2 thin film

This work proposes a new efficient, long-lasting scalable and low-cost triptych photocatalyst by assembling a semiconductor thin film (planar anatase TiO₂), a photosensitive molecule of the carbo-benzene (Cbz) family and plasmonic Ag nanoparticles with exquisite degree of intimacy with the semiconductor. Under simulated sunlight conditions over 48 h, the triptych TiO₂/Ag/Cbz photocatalyst allows a hydrogen production rate of 0.18 mmol g_{photocatalyst}⁻¹ h⁻¹ in conditions of applicative pressure (2.2 bars) and temperature (ambient) suitable for commercial applications. A ternary synergy (~33%) for hydrogen production is clearly evidenced with the triptych material in comparison with the diptych counterpart.The role of each component (TiO₂, Ag and Cbz) on the H₂ production is investigated systematically by discriminating the light absorption from the different materials and interfaces. We show how to achieve an efficient vertical Schottky junction between Ag nanoparticles and the TiO₂ substrate that is demonstrated to be of crucial importance in the water-splitting process.     

A novel photoelectrochemical cell with self-organized TiO2 nanotubes as photoanodes for hydrogen generation

A photoelectrochemical (PEC) cell with an innovative design for hydrogen generation via photoelectrocatalytic water splitting is proposed and investigated. It consisted of a TiO₂ nanotube photoanode, a Pt/C cathode and a commercial asbestos diaphragm. The PEC could generate hydrogen under ultraviolet (UV) light-excitation with applied bias in KOH solution. The Ti mesh was used as the substrate to synthesize the self-organized TiO₂ nanotubular array layers. The effect of the morphology of the nanotubular array layers on the photovoltaic performances was investigated. When TiO₂ photocatalyst was irradiated with UV-excitation, it prompted the water splitting under applied bias (0.6 V vs. Normal Hydrogen Electrode, NHE.). Photocurrent generation of 0.58 mA/cm² under UV-light irradiation showed good performance on hydrogen production.     

Photocatalytic hydrogen generation through water splitting on nano-crystalline LaFeO3 perovskite

Visible light active ABO₃ type photocatalyst with LaFeO₃ composition was synthesized by sol-gel method. The photocatalyst was characterized by different techniques such as X-ray diffraction, BET surface area analysis, particle size analysis, scanning electron microscopy, UV–visible diffuse reflectance spectroscopy (UV–Visible DRS), and photoluminescence spectroscopy. LaFeO₃ photocatalyst exhibited an optical band gap of 2.07 eV with the absorption spectrum predominantly in visible region of the spectrum. The BET surface area of photocatalyst LaFeO₃ was observed as 9.5 m²/g, with the crystallite size of 38.8 nm as calculated by the Debye-Scherer equation. The photocatalytic activity of LaFeO₃ was investigated for hydrogen generation through sacrificial donor assisted photocatalytic water splitting reaction by varying conditions in feasible parametric changes using visible light source, ethanol as a sacrificial donor and Pt solution of H₂PtCl₆ as a co-catalyst. The rate of photocatalytic hydrogen evolution was observed to be 3315 μmol g⁻¹ h⁻¹ under optimized conditions and using 1 mg dose of photocatalyst with reaction time of 4 h and illumination of 400 W.     

Hydrogen production from water splitting under UV light irradiation over Ag-loaded mesoporous-assembled TiO2-ZrO2 mixed oxide nanocrystal photocatalysts

Hydrogen production from the photocatalytic water splitting reaction is very attractive because it is an environmentally friendly process, where hydrogen is produced from two abundantly renewable sources, i.e. water and solar energy, with the aid of photocatalysts. TiO₂ is the most widely investigated photocatalyst; however, it alone still exhibits low performance to photocatalytically produce hydrogen. Hence, the aim of this work focused on the enhanced photocatalytic hydrogen production over Ag-loaded mesoporous-assembled TiO₂-ZrO₂ mixed oxide nanocrystal photocatalysts under UV light irradiation. The TiO₂-ZrO₂ mixed oxides with various TiO₂-to-ZrO₂ molar ratios were synthesized by a sol-gel process with the aid of a structure-directing surfactant, followed by Ag loading via a photochemical deposition method. The influences of photocatalyst preparation parameters, i.e. calcination temperature, phase composition, and Ag loading, were studied. The results revealed that the mesoporous-assembled TiO₂-ZrO₂ mixed oxide nanocrystal photocatalyst with a TiO₂-to-ZrO₂ molar ratio of 93:7 calcined at 500 °C exhibited the highest photocatalytic hydrogen production activity, and the Ag loading of 0.5 wt.% further greatly enhanced the photocatalytic activity of such TiO₂-ZrO₂ mixed oxide photocatalyst.     

Test of conductor and semiconductor electrocatalysts in high voltage alkaline electrolyzer as production media for green hydrogen

Despite the restricted success of conductor and semiconductor electrodes in solving hydrogen production problems, they provide a promising alternative to expensive conventional electrodes in water electrolysis investigations. Titanium dioxide (TiO₂) and silver (Ag) are widely used as photocatalysts in water splitting systems for hydrogen generation. Though TiO₂ is an inactive chemical semiconductor with poor conductivity, it has not been entirely investigated as an electrocatalyst yet. Two criteria were used to achieve this target: supplying high voltage to overcome the TiO₂ large band gap and immersing it in an alkaline solution to activate its inert surface. For comparison study, Ag noble metal nanoparticles coating was employed as a competitive electrocatalyst. In this regard, the application of Ag and TiO₂ coated on Ti electrodes in a hydrogen production system operated under high voltage was reported. The nanoparticles were synthesized using cost-effective and simple methods based on UV-deposition for Ag nanoparticles and the chemical precipitation method for TiO₂ nanoparticles. Then the synthesized nanoparticles were deposited on the Ti electrodes by simple immersion. The synthesized nanoparticles and coated electrodes were tested by XRD, SEM, and EDS to study their morphology, structure, particle size, and surface composition. Based on these results, TiO₂ nano-powder and coated electrodes exhibited homogenous spheres with a mixture of rutile and anatase phases, the majority being the anatase phase. The Ag-coated Ti substrate possessed a smaller crystallite size compared to TiO₂ coated substrate. To evaluate the performance of Ag/Ti and TiO₂/Ti electrodes toward hydrogen production, H₂ flow rates were measured in a 3.6 M KOH electrolytic solution at 6 V. Hydrogen flow rates obtained for pure Ti, Ag, and TiO₂ electrodes at a steady state were 21, 35, and 37 SCCM (standard cm³/min), respectively. Also, it was found that energy consumption was reduced when the electrodes were coated with nanoparticles. Furthermore, the electrolyzer's performance was assessed by calculating the hydrogen production efficiency and the voltage efficiency. The results showed that using TiO₂ electrodes gave the best hydrogen production and voltage efficiencies of 27% and 23%, respectively. This study brings new insights about Ag and TiO₂ coated electrodes in alkaline water electrolysis at high voltage regarding nanoparticle performance, hydrogen production, system performance, and energy consumption. In addition, minimizing the fabrication and operation costs of hydrogen production is the major enabler for the broad commercialization of water electrolysis devices.     

Light-assisted synthesis of Au/TiO2 nanoparticles for H2 production by photocatalytic water splitting

A series of Au/TiO₂ photocatalysts was synthesized via the light assistance through the photo-deposition for H₂ production by photocatalytic water splitting using ethanol as the hole scavenger. Effect of solution pH in the range of 3.2–10.0 on the morphology and photocatalytic activity for H₂ production of the obtained Au/TiO₂ photocatalysts was explored. It was found that all Au/TiO₂ photocatalysts prepared in different solution pH exhibited comparable anatase fraction (～0.84–0.85) and crystallite size of TiO₂ (21–22 nm), but showed different quantity of deposited Au nanoparticles (NPs) and other properties, particularly the particle size of the Au NPs. Among all prepared Au/TiO₂ photocatalysts, the Au/TiO₂ (10.0) photocatalyst exhibited the highest photocatalytic activity for H₂ production, owning to its high metallic state and small size of Au NPs. Via this photocatalyst, the maximum H₂ production of 296 μmol (～360 μmol/g?h) was gained at 240 min using the 30 vol% ethanol as the hole scavenger at the photocatalyst loading of 1.33 g/L under the UV light intensity of 0.24 mW/cm² with the quantum efficiency of 61.2% at 254 nm. The loss of the photocatalytic activity of around 20% was observed after the 5th use.     

One-pot synthesis of Cu–TiO2/CuO nanocomposite: Application to photocatalysis for enhanced H2 production,dye degradation & detoxification of Cr (VI)

Photocatalytic hydrogen production under the visible spectrum of solar light is an important topic of research. To achieve the targeted visible light hydrogen production and improve the charge carrier utilization, bandgap engineering and surface modification of the photocatalyst plays a vital role. Present work reports the one-pot synthesis of Cu–TiO₂/CuO nanocomposite photocatalyst using green surfactant -aided -ultrasonication method. The materials characterization data reveals the TiO₂ particle size of 20–25 nm and the existence of copper in the lattice as well as in the surface of anatase TiO₂. This is expected to facilitate better optical and surface properties. The optimized photocatalyst shows enhanced H₂ production rate of 10,453 μmol h⁻¹ g⁻¹ of the catalyst which is 21 fold higher than pure TiO₂ nanoparticles. The photocatalyst was tested for degradation of methylene blue dye (90% in 4 h) in aqueous solution and photocatalytic reduction of toxic Cr⁶⁺ ions (55% in 4 h) in aqueous solution. A plausible mechanistic pathway is also proposed.     

Photocatalytic H2 production from water splitting under visible light irradiation using Eosin Y-sensitized mesoporous-assembled Pt/TiO2 nanocrystal photocatalyst

Sensitized photocatalytic production of hydrogen from water splitting is investigated under visible light irradiation over mesoporous-assembled titanium dioxide (TiO₂) nanocrystal photocatalysts, without and with Pt loading. The photocatalysts are synthesized by a sol–gel process with the aid of a structure-directing surfactant and are characterized by N₂ adsorption–desorption analysis, X-ray diffraction, UV–vis spectroscopy, scanning electron microscopy, transmission electron microscopy and energy-dispersive X-ray analysis. The dependence of hydrogen production on the type of TiO₂ photocatalyst (synthesized mesoporous-assembled and commercial non-mesoporous-assembled TiO₂ without and with Pt loading), the calcination temperature of the synthesized photocatalyst, the sensitizer (Eosin Y) concentration, the electron donor (diethanolamine) concentration, the photocatalyst dosage and the initial solution pH is systematically studied. The results show that in the presence of the Eosin Y sensitizer, the Pt-loaded mesoporous-assembled TiO₂ synthesized by a single-step sol–gel process and calcined at 500 °C exhibits the highest photocatalytic activity for hydrogen production from a 30 vol.% diethanolamine aqueous solution with dissolved 2 mM Eosin Y. Moreover, the optimum photocatalyst dosage and initial solution pH for the maximum photocatalytic activity for hydrogen production are 3.33 g dm⁻³ and 11.5, respectively.     

Promoting hydrogen production by loading PdO and Pt on N–TiO2 under visible light

Nitrogen/titanium dioxide (N/TiO₂) visible light photocatalysts were prepared using the sol–gel method. The catalysts were characterized using transmission electron microscopy, reflective UV–visible spectroscopy, specific surface area measurements, and X-ray diffraction. The prepared catalysts were used to generate hydrogen gas through the water-splitting reaction under visible light (wavelengths greater than 400 nm). Various N/Ti addition ratios were tested, and the hydrogen generation rates were compared to determine the optimal ratio. The maximal hydrogen production rate (approximately 55 μmol h⁻¹ g⁻¹) was attained when the N/Ti ratio of N–TiO₂ was 10. When PdO and Pt were loaded onto the N–TiO₂ catalyst, the hydrogen generation rates increased to 544 and 772 μmol h⁻¹ g⁻¹, respectively. The highest hydrogen production rate (2460 μmol h⁻¹ g⁻¹) was obtained when bimetallic 0.05 wt% PdO-0.10 wt% Pt/N–TiO₂ was used. After three times use the hydrogen yield of the catalyst was maintained as 83%. A possible mechanism of water splitting catalyzed by this visible light photocatalyst is proposed.     

Highly efficient photocatalytic hydrogen evolution by using Rh as co-catalyst in the Cu/TiO2 system

Cu/TiO₂ was modified by adding Rh as co-catalyst and used as a highly efficient photocatalyst for the hydrogen evolution reaction. A low amount of Rh was loaded onto Cu/TiO₂ by the deposition-precipitation with urea (DPU) method to observe the effect on the hydrogen production displayed by different samples. The Rh–Cu/TiO₂ oxide structure exhibited a remarkably high photocatalytic hydrogen evolution performance, which was about twofold higher than that of the Cu/TiO₂ monometallic photocatalyst. This outstanding performance was due to the efficient charge carrier transfer as well as to the delayed electron-hole recombination rate caused by the addition of Rh. The influence of the different parameters of the photocatalyst synthesis and reaction conditions on the photocatalytic activity was investigated in detail. Hydrogen evolution was studied using methanol, ethanol, 2-propanol and butanol as scavengers with an alcohol:water ratio of 20:80. The methanol-water system, which showed the highest hydrogen production, was studied under 254, 365 and 450 nm irradiation; Rh–Cu/TiO₂ showed high photocatalytic activity with H₂ production rates of 9260, 5500, and 1940 μmol h^?1 g^?1, respectively. The Cu–Rh/TiO₂ photocatalyst was active under visible light irritation due to its strong light absorption in the visible region, low band gap value and ability to reduce the electron (e^?) and hole (h⁺) recombination.     

Rational regulation of vacancy species to manage migration paths of carriers in MoS2/TiO2 heterojunctions for efficient photocatalytic H2 generation

Photocatalytic water splitting to produce hydrogen (H₂), as one means to solve environmental pollution and energy shortage, is limited by the serious recombination of photogenerated electrons and holes, resulting in low solar energy conversion efficiency. Thus, steering the behaviors of charge carriers by rationally designing their transport pathway is essential, which can effectively suppress the recombination of electrons and holes. Herein, we designed a MoS₂/TiO₂ heterojunction with different vacancy species to manage the migration paths of photogenerated charge carriers. As demonstrated by experimental characterizations and density functional theory (DFT) calculations, oxygen and sulfur vacancies can induce defect energy levels in heterostructures, which can capture photogenerated holes and electrons, respectively, resulting in substantially promoted charge separation efficiency and longer lifetime of electrons. As expected, the optimized photocatalyst shows a stable H₂ production rate of 1.41 mmol g^?1 h^?1, which is significantly better than that of the bare MoS₂/TiO₂ heterojunction. This finding informs the significance in rational design of the nanostructures for promoting the photocatalytic performance.     

Boundary effect of Ag/TiO2 on catalytic H2O splitting for H2 production: A theoretical account

Ag supported on TiO₂ reveals advantages in photocatalytic H₂O splitting due to its synergistic effects for promoting the e^?/h⁺ separation. The structural and electronic characteristics of Ag/TiO₂, as well as adsorption and splitting of H₂O on different sites, were investigated employing the density functional theory calculations. The analysis of density of states and electrons densities evidenced the electron transfer and hybrid between Ag and TiO₂. The boundary was especially reactive toward the target species being the most active site, and thus electrons could be transferred to the adsorbate through the supported Ag atoms, leading to the generation of Schottky barrier, which inhibited the recombination of photogenerated electron-hole pairs. The O–H bond cleavage with the E_a of 2.18 eV was the rate-determining step for H₂ production on the Ag/TiO₂ boundary. Fukui functions indicated the outermost Ag cluster site on Ag/TiO₂ boundary exhibited high electron transferability and H₂ production tendency.