Simultaneous co-doping of RuO2 and IrO2 into anodic TiO2 nanotubes: A binary catalyst for electrochemical water splitting

The simultaneous doping of RuO₂ and IrO₂ catalysts into anodic TiO₂ nanotubes (NTs) was successfully achieved by single-step anodization. KRuO₄ was used as the precursor for the RuO₂ dopant. However, for IrO₂ doping, IrO_x nanoparticles (NPs) were synthesized from IrCl₃ as an intermediate species to avoid damage to the NTs by chloride ions during doping. ${{\text{IrO}}_4}^{\mathrm{?}}$ generated from the IrO_x NPs through selective dissolution in the electrolyte was simultaneously doped into the positively biased TiO₂ NTs along with RuO₂. The structural features, NT length, and amount of catalyst doping were controlled by the concentration of HF in the electrolyte and the anodizing time. The binary-catalyst-doped TiO₂ NTs exhibited an outstanding onset potential of 0.84 V for the oxygen evolution reaction (OER). In addition, the amount of O₂ gas evolved during the OER at 2.0 V was measured to be 230 μmol cm^?2 min^?1 by gas chromatography, which corresponds to a faradaic efficiency of 99%. The major oxidation states of the metals in the catalysts were found to be Ru⁴⁺ and Ir⁴⁺ by X-ray photoelectron spectroscopy and transmission electron microscopy selected area electron diffraction analysis, indicating the presence of RuO₂ and IrO₂ in the TiO₂ NTs.     

Photoelectrocatalytic hydrogen production of heterogeneous photoelectrodes with different system configurations of CdSe nanoparticles,Au nanocrystals and TiO2 nanotube arrays

The different configurations of CdSe nanoparticles, Au nanocrystals and TiO₂ nanotube arrays play an important role in the photoelectrochemical behavior and photoelectrocatalytic hydrogen production of this heterogeneous photoelectrode system. It is discovered that the photoelectrocatalytic hydrogen production of the TiO₂–CdSe–Au photoelectrode (1.724 mmol g⁻¹ h⁻¹) is about 4 times that of the TiO₂–Au–CdSe photoelectrode (0.430 mmol g⁻¹ h⁻¹) under visible light irradiation. From the comprehensive investigation of their photoelectrochemical behaviors, it is illustrated that the interfacial electrical field has distinct effects on the separation and transportation of photogenerated carriers in these heterostructure photoelectrodes. The directions of the interfacial electrical fields formed at TiO₂–Au and Au–CdSe interfaces are opposite in the TiO₂–Au–CdSe photoelectrode, which hinders the separation of photogenerated electron-hole pairs and subsequent transportation of photogenerated carriers. On the contrary, the directions of the interfacial electrical fields formed at TiO₂–CdSe and CdSe–Au interfaces are identical in the TiO₂–CdSe–Au photoelectrode, which promotes the separation of photogenerated excitons and subsequently enhances their transportation for enlarged photocurrent density. The results of photoelectrocatalytic hydrogen production also confirm our assumption.     

Shape-dependent performance of gold nanocrystals supported on TiO2 for photoelectrochemical water oxidation under different radiations

A number of studies are documented for enhanced solar energy conversion of titanium dioxide (TiO₂) by surface modification with gold (Au) nanostructures. Herein, Au nanocrystals of different geometry (spherical, cubes, triangles and wires) are synthesized and immobilized on TiO₂ (bare and nitrogen–doped) surface. The shape–dependent performance of the as-prepared photocatalysts is evaluated by studying water oxidation, both under UV–visible and visible illuminations. As expected, a strong dependency of PEC performance on the shape of Au nanocrystals is discerned. Also, the trend of performance under UV–visible is different than that of visible radiation, suggesting a distinct charge transport mechanism. In addition, the photocatalytic performance increases under visible light while decreases under UV–visible with increasing Au loading. A schematic is proposed showing a likely interfacial electron transfer reaction between Au nanostructures and TiO₂, depending on illuminating wavelength. The performance variation in the as-prepared photoelectrodes is correlated to particle size, optical properties and electrical conductivity.     

Aging effect of diethanolamine stabilized sol on different properties of TiO2 films: Electrochromic applications

Diethanolamine derived clear precursor sol has been utilized for the deposition of TiO₂ films annealed at 470 °C for 5 min. Effect of the precursor sol's aging on different properties of the films has been examined in the present study. Films obtained from aged sol have exhibited superior electrochemical (diffusion coefficient—2.46×10⁻¹⁰ cm² s⁻¹) and electrochromic characteristics due to enhanced Li ion insertion upon application of electric field. The aged sol derived films have exhibited a higher optical modulation (40% at 550 nm) between the colored and bleached states. The ion storage capacities of the films derived from freshly prepared and aged sols are 4.1 and 8.1 mC cm⁻², respectively, upon applied voltage of ±1.5 V. X-ray diffraction studies have affirmed an increase in the TiO₂ crystallite size upon the use of aged sol for the deposition of films. FTIR investigations have confirmed the conversion of Ti–O–Ti to Ti–O network in the aged sol derived films. SEM studies have evidenced porosity changes in films obtained from the sol aged for different durations. The index of refraction as measured by the ellipsometry method corroborates the SEM results and shows reduced porosity (pore size—38 nm) in films derived from the sol just reaching the state of gelation. Thickness of the aged sol derived film is measured to be the highest i.e. 350 nm. Energy bandgaps of the films for both direct and indirect transitions tend to decrease as a function of sol's aging.     

Sonochemical reduction method for synthesis of TiO2Pd nanocomposites and investigation of anode and cathode catalyst for ethanol oxidation and oxygen reduction reaction in alkaline medium

The development of the superior Pt-free electrocatalyst for enhancing electrocatalytic activity and stability towards the EOR (ethanol oxidation reaction) and ORR (oxygen reduction reaction) are very important for the commercialization of fuel cells. In this work, the palladium nanoparticles (Pd NPs) deposited on titanium dioxide nanospheres (PdTiO₂) were successfully prepared by the sonochemical reduction method. Hence, the TiO₂ nanospheres were directly used as the templates for nucleation and growth of Pd NPs over their surface using PdCl₄⁻ as the Pd precursor, PVP (Polyvinylpyrrolidone) as the stabilizer, ascorbic acid (AA) as the reducing agent, and water as the solvent. The size of Pd NPs is remarkably controlled using the sequential reduction steps by adding an excess of PdCl₄⁻. The excellent electrocatalytic activity towards EOR and ORR is ascribed by the synergistic effect of the Pd nanoparticles and TiO₂ nanospheres support. This unique nanocomposite should be of great benefit to the construction of commercial fuel cell systems.     

Hybrid solar cells based on MEH-PPV and thin film semiconductor oxides (TiO2, Nb2O5, ZnO, CeO2 and CeO2–TiO2): Performance improvement during long-time irradiation

Performance improvement of hybrid solar cells (HSC) applying five different thin film semiconductor oxides has been observed during long-time irradiation in ambient atmosphere. This behavior shows a direct relation between HSC and oxygen content from the environment. Photovoltaic devices were prepared as bi-layers of thin film semiconducting oxides (TiO₂, Nb₂O₅, ZnO, CeO₂–TiO₂ and CeO₂) and the polymer MEH-PPV, with a final device configuration of ITO/Oxide_{thin film}/MEH-PPV/Ag. The oxides were prepared as thin transparent films from sol–gel solutions. The photovoltaic cells were studied in ambient atmosphere by recording the initial values of open circuit voltage (V_oc) and current density (I_sc). Solar decay curves presented as the measurement of the short circuit current as a function of time, IV curves and photophysical analyses were also carried out for each type of device. Solar cells with TiO₂ thin films showed the best performance with maximum V_oc as high as −0.74 V and I_sc of 0.4 mA/cm². Solar decay analyses showed that the devices require a stabilization period of several hours in order to reach maximum performance. In the case of TiO₂, Nb₂O₅ and CeO₂–TiO₂, the maximum current density was observed after 15 h; for CeO₂, the maximum performance was observed after 30 h. The only exception was observed with devices applying ZnO in which the current density decreased drastically and degraded the polymer in just a couple of hours.     

Surveying the hybrid of radiation and magnetic parameters on Maxwell liquid with TiO2 nanotube influence of different blades

In this paper, the impacts of Maxwell nanoliquid transmission, rectangular with titanium oxide nanoparticles are explored over the triangular, chamfer blades. The innovation of this paper is the use of the number of chamfers, rectangular, and triangular blades at the top and bottom of a stretched plate to study physical nanofluid parameters such as temperature and the effects of magnetism. Also, by determining the appropriate height and length for the blades, we achieve the best optimization of temperature and velocity of nanofluid between the plate and the blades, which improves heat transfer and with a more and better effect of magnetic effects. The finite element method is utilized for the calculated differential equations. In this paper, by utilizing the reaction surface strategy, we optimized the titanium oxide nanofluid velocity and temperature, and magnetic parameter passing from the extending sheet. On average, the titanium oxide nanoparticle velocity around the two rectangular blades at the beginning of the sheet is 73.09% higher than triangular blades and 66.98% higher than chamfer blades. Based on the outcomes got from the titanium oxide nanofluid speed charts and the warm exchange cantors and magnetic impacts within the Design-Expert computer program, the most excellent optimization occurred for TiO₂ nanofluid speed and TiO₂ nanofluid temperature and TiO₂ magnetic parameter with u = 0.523, T = 3.25, and H = 2.671.     

A comparative study on photoelectrochemical activity of ZnO/TiO2 and TiO2/ZnO nanolayer systems under visible irradiation

TiO₂/ZnO and ZnO/TiO₂ nanolayer thin films were synthesized using sol-gel method. Optical analysis revealed high transmittance of the films in the visible range with almost the same bandgap energy for the both systems. XPS technique shows stoichiometric formation of TiO₂ and ZnO on the surface of TiO₂/ZnO and ZnO/TiO₂ layers, respectively. According to AFM observations and its data analysis, the TiO₂/ZnO films exhibited a higher surface roughness and more effective interfaces with electrolyte during redox reactions. Based on photoelectrochemical measurements, TiO₂/ZnO nanolayer photoanode possesses a lower charge transfer resistance and higher transient time for charge carriers (e⁻ and h⁺) and hence a higher photocurrent density under visible light irradiation as compared with the ZnO/TiO₂ nanolayer system.     

Photoelectric characterization of Cu(In,Ga)S2 solar cells obtained from rapid thermal processing at different temperatures

CuInS₂-based solar cells have a strong potential of achieving high efficiencies due to their ideal band gap of 1.5 eV. A further increase in the efficiency is expected from doping the absorber film with gallium due to enlargement of the band gap (E_g) and correspondingly the open-circuit voltage (V_OC). We investigated Cu(In,Ga)S₂ solar cells obtained from stacked metal layers sputtered from In and (Cu,Ga) targets followed by rapid thermal processing (RTP) in sulfur vapor. Depending on the actual RTP temperature profile, the films might exhibit CuInS₂/CuGaS₂ (top/bottom) segregation, which is rather detrimental for a large V_OC. We found that only precursors sulfurized at sufficiently high temperatures exhibit the desired interdiffusion of the segregated CuInS₂/CuGaS₂ layers resulting in an increased V_OC. Moreover, temperature dependent current-voltage profiling (suns-V_OC-analysis) yielded strong indications for improved current collection and reduced losses for devices with proper interdiffusion of the CuInS₂/CuGaS₂ layers. A more fundamental question is related to the variation and formation of defect states in differently processed absorber films. The studied samples were thus further investigated by means of admittance spectroscopy, which allowed us to confirm the presence of three individual defect states in both absorber configurations. Two defects exhibit activation energies, which remain unchanged upon varying the RTP temperature whereas a third state exhibits significantly increased activation energy in devices showing interdiffusion of CuInS₂/CuGaS₂ layers. According to the characteristic shift of the conduction band edge upon Ga-doping we conclude that the latter defect level corresponds with the minority carriers in the p-type absorbers.     

Functionalized carbon dots on TiO2 for perovskite photovoltaics and stable photoanodes for water splitting

Various types of fluorescent carbon nanoparticles, often called carbon dots (CDs), are synthesized by different polycondensation methods: microwave irradiation, hydrothermal conditions or solution chemistry at ambient temperature with subsequent chemical functionalization. The CDs are deposited on TiO₂ films to be probed as electron transport layers in perovskite photovoltaics and the anode for photoelectrochemical water splitting. Nitrogen CDs, which do not contain oxygen, lead to an increase of around 50 mV in the open circuit voltage of perovskite solar cells. All the CD types produce an improved photocurrent in water splitting, particularly CDs that are functionalized with thiol groups and butyl chains. It is demonstrated that the modified electrode is stable under continuous operation. Other electrochemical characteristics of the electrode, such as the voltammogram shape, onset potentials and open circuit potentials, remain nearly unchanged upon the deposition of CDs. Only the incident photon to current conversion efficiency improves clearly, extending the absorption range by around 20 nm towards longer wavelengths. This study provides new data about mechanisms and electrode arrangements for improving the performance of n-type semiconductors in photovoltaic cells and photoelectrochemical hydrogen production.     

Effect of single-cation doping and codoping with Mn and Fe on the photocatalytic performance of TiO2 thin films

TiO₂ thin films with varying Mn and Fe dopant levels (0.01–5.00 mol% metal basis; single cation doping and codoping) were deposited on soda-lime-silica glass substrates by spin coating, followed by annealing in air at 450 °C for 2 h. The mineralogical, morphological, optical, and photocatalytic properties of the thin films were determined. The fabricated films were ∼250 nm thick and they were comprised of grains of ∼20–30 nm size. Anatase (or amorphous titania) was the only phase in essentially all the films, with the dopants' being soluble in anatase. All of the films were transparent (∼80%) in the visible region and the optical indirect band gaps were ∼3.4 eV. Photocatalytic testing (≤24 h) showed that the extent of photodegradation decreased with increasing dopant levels. The 0.01 mol% Fe-doped sample showed the best photoactivity since, at this doping level, the negative effects of electron/hole recombination and lattice distortion probably were minimal.     

CuOx dispersion and reducibility on TiO2 and its impact on photocatalytic hydrogen evolution

Nanostructured CuO_x/TiO₂ (a mixture of Cu/Cu₂O/CuO) was prepared by impregnation for enhancing photocatalytic hydrogen generation from an aqueous solution containing 10 v/v% methanol. At an optimum Cu loading of 0.5 wt% and a calcination temperature of 500 °C, the CuO_x was present as relatively highly dispersed (0.90), fine deposits. At Cu loadings beyond 0.5 wt% a bimodal distribution of CuO_x deposits appeared with the prevalence of larger Cu deposits increasing with increasing Cu content. A corresponding decrease in H₂ generation was observed as Cu loading increased which was attributed to the increasing presence of the larger CuO_x deposits. The particle calcination temperature (in air) was also found to affect CuO_x/TiO₂ activity with an optimum performance achieved at a temperature of 300 °C. Calcining the CuO_x/TiO₂ at 500 °C led to greater oxidation of the CuO_x deposits (∼40%) to form more Cu²⁺ which corresponded to an almost proportional (42%) decrease in H₂ generation. The findings demonstrate the importance of Cu dispersion and oxidation state in governing photocatalytic H₂ generation by CuO_x/TiO₂.     

Enhanced electrocatalytic activity and stability of Pd nanoparticles supported on TiO2-modified nitrogen-doped carbon for ethanol oxidation in alkaline media

TiO₂-modified nitrogen-doped carbon (TiO₂-NC), prepared by a polymerization-pyrolysis process, is used to support the Pd catalyst for ethanol oxidation reaction (EOR) in alkaline media. X-ray photoelectron spectroscopy characterization indicates that the incorporation of TiO₂ and nitrogen into the carbon matrix could improve the percentage of Pd⁰ in Pd/TiO₂-NC catalyst. Electrochemical characterization shows that the Pd/TiO₂-NC catalyst presents higher electrocatalytic activity and stability for EOR than the nitrogen-doped carbon-supported Pd (Pd/NC) catalyst and the carbon black-supported Pd (Pd/CB) catalyst, which can be mainly attributed to the high percentage of Pd⁰ in Pd/TiO₂-NC catalyst (65%) than those in Pd/NC (48%) and Pd/CB (31%) catalysts. The results indicate that the Pd/TiO₂-NC catalyst holds great potential as high-performance anode catalyst for direct ethanol fuel cells.     

Experimental and numerical study of forced convection heat transfer in different internally ribbed tubes configuration using TiO2 nanofluid

TiO₂/water nanofluid is used together with a ribbed tube for heat transfer augmentation. This paper presents an experimental and numerical investigation to study the influence of the ribs' pitch distance and ribbed tube configuration on heat transfer using TiO ₂ nanofluid in a turbulent regime with Reynolds numbers of 5000‐40 000. Meanwhile, the fluid properties are assumed to be constant with temperature under uniform heat flux. The average nanoparticle size is 50 nm and volume fractions of 0% to 1% are adopted. The study is accomplished by using the finite volume method, and its objective involves finding a low friction factor and high heat transfer enhancement in the presence of TiO ₂/water nanofluids. In comparison with the plain tube, a helical ribbed tube provides higher performance evaluation criteria (about 2.0%), while circumferentially ribbed tube provides 1.9% and longitudinal ribbed tube provides 1.88%. The helical ribbed tubes with a 5.89 mm pitch distance gave higher turbulent kinetic energy due to a stronger swirl intensity, resulting in a thinner thermal boundary layer and a higher Nusselt number with uniform distribution. The nonlinear models of friction factor and Nusselt number have been predicted with a maximum deviation of ±3% and ±2%, respectively.     

Synthesis and sintering of Gd-doped CeO2 electrolytes with and without 1 at.% CuO dopping for solid oxide fuel cell applications

Nano-sized Ce_0.8Gd_0.2O_2−δ and Ce_0.79Gd_0.2Cu_0.01O_2−δ electrolyte powders were synthesized by the polyvinyl alcohol assisted combustion method, and then characterized by powder characteristics, sintering behaviors and electrical properties. The results demonstrate that the as-synthesized Ce_0.8Gd_0.2O_2−δ and Ce_0.79Gd_0.2Cu_0.01O_2−δ possessed similar powder characteristics, including cubic fluorite crystalline structure, porous foamy morphology and agglomerated secondary particles composed of gas cavities and primary nano crystals. Nevertheless, after ball-milling these two powders exhibited quite different sintering abilities. A significant reduction of about 400 °C in densification temperature of Ce_0.79Gd_0.2Cu_0.01O_2−δ was obtained when compared with Ce_0.8Gd_0.2O_2−δ. The Ce_0.79Gd_0.2Cu_0.01O_2−δ pellets sintered at 1000 °C and the Ce_0.8Gd_0.2O_2−δ sintered at 1400 °C exhibited relative densities of 96.33% and 95.7%, respectively. The sintering of Ce_0.79Gd_0.2Cu_0.01O_2−δ was dominated by the liquid phase process, followed by the evaporation-condensation process, Moreover, Ce_0.79Gd_0.2Cu_0.01O_2−δ shows much higher conductivity of 0.026 S cm⁻¹ than Ce_0.8Gd_0.2O_2−δ (0.0065 S cm⁻¹) at a testing temperature of 600 °C.     

Dehydrogenation kinetics of MgH2-based hydrogen storage tank at different operating temperatures and mass flow rates

The most efficient electrical production from fuel cells integrated with hydride-based hydrogen storage tanks is obtained from suitable dehydrogenation kinetics, facilitating constant flow rate of hydrogen supply for a long period of time. Dehydrogenation kinetics of hydride-based tanks depends strongly on operating temperatures and system pressures, relating to hydrogen mass flow rate (H₂-FR) released from the tank. Since a cylindrical tank (96.2 mL) mounted with central heat exchanger containing TiF₄-MWCNT-MgH₂ (～45 g) shows excellent de/rehydrogenation and reversibility (5.4 wt % H₂ upon 20 cycles), the effects of different operating conditions (T = 300–340 °C and H₂-FR = 0.6–1.0 standard L/min) on kinetic properties of this MgH₂-based tank are of significant interest. Kinetic properties either rapid or steady-state desorption can be optimized by tuning the operating temperature and H₂-FR simultaneously. Moreover, the performances in the axial and radial directions of the tank as well as kinetic behaviors and rate-limiting step during dehydrogenation at different temperatures and H₂-FR of MgH₂-based tank are investigated.     

Electrochemical and XAS investigation of oxygen reduction reaction on Pt-TiO2-C catalysts

Pt-TiO₂-C composites with different titanium oxide loading were synthesized by photo-deposition and chemical vapor deposition methods. The changes in their electronic properties improve the electrochemical activity toward the oxygen reduction reaction (ORR) compared to the Pt-C catalyst synthesized at the same conditions. The platinum samples were physically characterized by means of Transmission Electron Microscopy (TEM), Small Angle X-ray Scattering (SAXS), X-ray Absorption Spectroscopy (XAS) and X-ray Photo-electron Spectroscopy (XPS). Their electrochemical activity was also investigated by cyclic and linear voltammetry techniques. TEM analysis shows homogeneously dispersed platinum nanoparticles with an average particle size of 2 nm in all the synthesized samples. Form factor (morphology model) and particle size were determined by SAXS, the data adjusted to spherical Pt nanoparticles in both synthesis methods. XAS studies at the Pt L₃-edge shows a close interaction of Pt with the support material, i.e. C or TiO₂. XPS analysis reveals surface modifications that induce electronic changes on Pt-TiO₂-C. Significant differences in the ORR electrochemical activity were correlated to the TiO₂ loading and the synthesis procedure.     

Effects of anatase TiO2 with different particle sizes and contents on the stability of supported Pt catalysts

Pt/TiO₂-C catalyst with TiO₂ and carbon black as the mixed support has been synthesized by the microwave-assisted polyol process (MAPP). Effects of anatase TiO₂ with different particle sizes and contents on the stability of supported Pt catalysts have been systematically studied. X-ray diffraction (XRD), transmission electron microscopy (TEM), cyclic voltammograms (CV), and accelerated potential cycling tests (APCT) have been carried out to present the influence degree. The experimental results indicate that the original electrochemically active specific surface areas (ESA) of the catalysts decrease with the increase of mean particle sizes of TiO₂ and TiO₂ contents. However, the activity of Pt/TiO₂-C-20 is very close to that of Pt/TiO₂-C-5 and the stability of Pt/TiO₂-C-20 is the best after 1000 cycles APCT, illustrating that the optimized particle size of TiO₂ in Pt/TiO₂-C catalyst is 20 nm. Furthermore, the stability of the catalysts increase with the increase of TiO₂ contents in the mixed support. Taking into account both the activity and stability of various Pt/TiO₂-C catalysts, the optimized particle size of TiO₂ is 20 nm and the optimal TiO₂ content existed in the mixed support is 40%.     

Effects of H2/O2 and H2/O3 gases on PtMo/C cathode PEMFCs performance operating at different temperatures

This study reported the activity of catalysts synthesized from platinum and molybdenum alloys in different atomic ratios and used as cathode electrocatalysts in the PEMFC. The structural properties of PtMo/C and Pt/C catalysts were analyzed by XRD analysis. The composition and distribution of these alloys in Vulcan XC-72R Carbon were determined by SEM and EDX techniques. CV studies assessed electrochemical properties such as ORR and ECSA activity. The performance of PEMFC cathodes that supplied pure hydrogen and oxygen was examined using polarization curves at different temperatures. Another way to improve the cathodic reaction is to use ozone as a potent oxidizing agent. It was measured that the OCV of the H₂/O₃ PEM fuel cell was 1.60 V, much greater than the open circuit voltage of the traditional H₂/O₂ PEM fuel cell. The PtMo/C catalyst achieved its highest power density of 137 mWcm⁻² at 70 °C, 128 mWcm⁻² at 60 °C, 101 mWcm⁻² at 50 °C, and 85 mWcm⁻² at 40 °C when exposed to H₂/O₂. As the temperature of the cell was raised, it was seen that the catalyst's catalytic activity increased.The maximum power density was detected to be inversely related to the rise in temperature when ozone was used. At low current densities, however, ozone was observed to greatly boost activation polarization.     

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.