Materials For Solar Energy Conversion Research Articles

Tracking Charge Transfer to Residual Metal Clusters in Conjugated Polymers for Photocatalytic Hydrogen Evolution

Semiconducting polymers are versatile materials for solar energy conversion and have gained popularity as photocatalysts for sunlight-driven hydrogen production. Organic polymers often contain residual metal impurities such as palladium (Pd) clusters that are formed during the polymerization reaction, and there is increasing evidence for a catalytic role of such metal clusters in polymer photocatalysts. Using transient and operando optical spectroscopy on nanoparticles of F8BT, P3HT, and the dibenzo[b,d]thiophene sulfone homopolymer P10, we demonstrate how differences in the time scale of electron transfer to Pd clusters translate into hydrogen evolution activity optima at different residual Pd concentrations. For F8BT nanoparticles with common Pd concentrations of >1000 ppm (>0.1 wt %), we find that residual Pd clusters quench photogenerated excitons via energy and electron transfer on the femto-nanosecond time scale, thus outcompeting reductive quenching. We spectroscopically identify reduced Pd clusters in our F8BT nanoparticles from the microsecond time scale onward and show that the predominant location of long-lived electrons gradually shifts to the F8BT polymer when the Pd content is lowered. While a low yield of long-lived electrons limits the hydrogen evolution activity of F8BT, P10 exhibits a substantially higher hydrogen evolution activity, which we demonstrate results from higher yields of long-lived electrons due to more efficient reductive quenching. Surprisingly, and despite the higher performance of P10, long-lived electrons reside on the P10 polymer rather than on the Pd clusters in P10 particles, even at very high Pd concentrations of 27000 ppm (2.7 wt %). In contrast, long-lived electrons in F8BT already reside on Pd clusters before the typical time scale of hydrogen evolution. This comparison shows that P10 exhibits efficient reductive quenching but slow electron transfer to residual Pd clusters, whereas the opposite is the case for F8BT. These findings suggest that the development of even more efficient polymer photocatalysts must target materials that combine both rapid reductive quenching and rapid charge transfer to a metal-based cocatalyst.

Mo thio and oxo-thio molecular complexes film as self-healing catalyst for photocatalytic hydrogen evolution on 2D materials

2D semiconducting nanosheets of Transition Metal Dichalcogenides are attractive materials for solar energy conversion because of their unique absorption properties. Here, we show that Mo thio- and oxo-thio-complexes anchored on 2D p-WSe2 nanosheets considerably boost water splitting under visible light irradiation with photocurrent density up to 2.0 mA cm−2 at -0.2 V/NHE. Besides developing high electro-catalytic activity, the Mo-complexes film is also shown to be capable of healing surface defects. We propose that the observed healing of surface defects arises from the strong adsorption on point defects of the 2D WSe2 substrate of Mo complexes such as (MoS4)2-, (MoOS3)2-, (Mo2S6O2)2- as supported by DFT calculations. In addition, the thio-, oxo-thio Mo complexes films are shown to enhance charge carrier separation and migration favouring the hydrogen evolution reaction, putting forward the use of thio-, oxo-thio-Mo complexes as a multicomponent passivation layer exhibiting multiple properties.

Enhanced photoelectrochemical efficiency and stability using nitrogen-doped TiO2 on a GaAs photoanode

GaAs has been attracting significant attention as a material for solar energy conversion because of its visible light absorption capability, high electron mobility, and direct band gap. However, its chemical stability is extremely low for utilization in applications associated with photoelectrochemical water splitting. TiO2 is known to exhibit an excellent chemical stability; however, it has a poor electrical conductivity and a wide band gap. In this study, we fabricated a heterogeneous Z-scheme photoanode by combining TiO2 and GaAs; this photoanode demonstrated a high chemical stability and a high visible light absorption capability. Herein, we propose an effective strategy for achieving nitrogen doping in TiO2 (N-TiO2) to form oxygen vacancies and TiN, which increase the electrical conductivity and reduce the overpotential of the photoanode. The TiN/N-TiO2/ITO/GaAs photoanode thus obtained significantly improved the electrochemical performances of the oxygen evolution reaction, as compared to those obtained with the undoped TiO2/ITO/GaAs photoanode. Further, the Tafel slope was observed to decrease from 315.4 mV/dec to 64.1 mV/dec and the open circuit potential shifted from 0.2 V to −0.2 V vs RHE. In addition, photoelectrochemical stability was significantly improved as compared to that obtained by bare GaAs.

Hybrid nanostructures for solar-energy-conversion applications

Solar energy harvesting through photovoltaic conversion is the most promising technology for renewable energy production. Nanoscience and nanotechnology have enabled the development of hybrid and multifunctional materials for harnessing solar energy. Hybrid nanomaterials consist of more than two nanomaterials to improve the individual performance of the components. In this paper, the authors explain and review two approaches to solar energy harvesting – namely, photovoltaic and photosynthetic. Natural photosynthetic biomaterials such as photosystem I, photosystem II, proteins and bacteria extracted from various leaves, plants or fruits can be used with inorganic nanomaterials to enhance the efficiencies of hybrid solar cells. The authors review biohybrid solar cells based on various natural dyes and nanostructures such as quantum dots, nanotubes, thin films and bulk nanoparticles. Biohybrid nanostructures have the potential to absorb almost 100% light, and hence, they can exhibit an extraordinary efficiency of up to 100%. Artificial photosynthetic systems such as photoelectrochemical cells may be built using biohybrid materials for solar energy conversion at a low cost and in an eco-friendly manner. Biohybrid nanostructured light-harvesting devices are desirable for high efficiency with a wide spectral response. Hybrid solar cells can change the path of next-generation hybrid solar cell technology.

Engineering Cells, Membranes and Light Harvesting/Photosystem II Super-Complexes in Bio-Photoelectrochemical Cells

Photosynthetic organisms, membranes and complexes are attractive starting materials for solar energy conversion (SEC). Our overall goal is to develop methods to perform SEC using these materials in simple, inexpensive and a fashion that will be non-polluting and will not compete with the growth of food materials. I will describe here how the remarkable photocatalytic activity of the photosynthetic apparatus can provide overall water splitting with oxygen and hydrogen production in Bio-Photo-Electro-Chemical (BPEC) cells via the simplest and cleanest of processes wither in the absence or presence of added electron transport molecules. With plant thylakoids, electrons are shuttled by FeCN to a transparent FTO electrode, yielding a photocurrent density of 0.5 mA·cm-2. Hydrogen evolution occurs at the cathode at a bias as low as 0.8 V. A tandem cell comprising the BPEC cell with the thylakoid membranes and a Si photovoltaic module achieves overall water splitting with solar to hydrogen conversion efficiency of 0.3% (Pinhassi et al. Nature Communications 2016). With cyanobacterial cells, following a brief treatment that does not induce loss of cell viability, electrons from both the respiratory and photosynthetic systems are transferred directly to a graphite electrode, utilizing endogenous electron carriers (Saper et al. Nature Communications 2018). The current produced can be used for hydrogen production at low additional bias for significantly longer durations than the plant thylakoids.Another route is to isolate the photosynthetic complexes and chemically connect them to the electrochemical cell. One of the issues with this strategy is the small number of light absorbing chromophores connected to the complex, lowering the photochemical efficiency. Connection of isolated light harvesting complexes can help to overcome this deficiency. Photosystem II (PSII) is the only enzyme that catalyzes light-induced water oxidation being the basis for its application as a biophotoanode in various bio-photovoltaics and photo-bioelectrochemical cells. However, the absorption spectrum of PSII limits the quantum efficiency in the range of visible light, due to a gap in the green absorption region of chlorophylls (500 - 650 nm). To overcome this limitation, we have stabilized the interaction between PSII and Phycobilisomes (PBSs) – the cyanobacterial light harvesting complex, in vitro. The PBS of different cyanobacteria were analyzed for their ability to transfer energy to Thermosynechococcus elongatus (Te) PSII by fluorescence spill-over and photocurrent action spectra. Integration of the PBS-PSII super-complexes within an Os-complex-modified hydrogel on macro-porous indium tin oxide electrodes (MP-ITO) resulted in notably improved, wavelength dependent, incident photon-to-electron conversion efficiencies (IPCE). IPCE values in the green gap were doubled from 3 % to 6 % compared to PSII electrodes without PBS and a maximum IPCE up to 10.9 % at 670 nm was achieved. Figure 1

Mo Thio and Oxo-Thio Molecular Complexes As Water-Soluble Self-Healing Catalysts for Photocatalytic Hydrogen Evolution on 2D Materials

2D semiconducting nanosheets of Transition Metal Dichalcogenides are attractive materials for solar energy conversion because of their unique absorption properties. Recently, Hydrogen evolution reaction (HER) was achieved with thin 2D WSe2 nanosheets activated by well-known precious metal catalysts. Here, we propose for the first time, water-soluble, noble-metal-free, Mo thio- and oxo-thio-complexes anchored on 2D p-WSe2 nanosheets for efficient water splitting under visible light irradiation with photocurrent density up to 2.0 mA cm-2 at -0.2 V/NHE. These Mo thio and oxo-thio- molecular complexes represent an ideal class of catalysts, well-suited to functionalize 2D materials since they are stable in aqueous environments, cheap, environmentally benign to synthesize and process. We propose that the high performances of the oxo thio-Mo complexe catalysts arise from the strong adsorption on point defects of the 2D WSe2 substrate of Mo complexes such as (MoS4)2-, (MoOS3)2-, (Mo2S6O2)2- as shown from DFT calculations. More particularly, advantages of the water-soluble oxo-thio Mo complexes distributions, which spontaneously formed at well-defined pH are highlighted owing to their high electro-activity combined with their strong affinity toward point defects.

(Invited) Photoelectrochemical Solar Fuel Production Using Organic Semiconductors

Pi-conjugated carbon-based semiconductors are well-established as high-performance and easily-processed materials for inexpensive and scalable solar energy conversion in organic photovoltaic (OPV) devices, but their promise in the economic conversion of solar energy into chemical energy (solar fuels) has only recently been recognized. In this presentation, I will discuss the main approaches for employing organic semiconductor-based devices towards solar H2 generation via water splitting and review the state-of-the-art.[1] OPV-biased water electrolysis has advanced significantly, now exceeding 6% solar-to-hydrogen conversion efficiency. However, the direct water splitting by an organic semiconductor in a photoelectrochemical cell, which has attractive advantages, remains limited by the intrinsic stability of organic semiconductors when placed in direct junction with aqueous electrolyte. I will further present experimental insights into the operational stability of donor:acceptor bulk heterojunction photocathodes and photoanodes[2] with an organic/water interface. Using sacrificial redox couples and various electrochemical analysis including impedance spectroscopy we identify and quantify the key factors that govern long-term photoactivity (>12 h). These insights can be extended to overall water splitting with appropriate catalyst overlayer design. Overall our advances with organic semiconductor photoelectrodes open a new path for economically feasible solar fuel production.[1] L. Yao, A. Rahmanudin, N. Guijarro, K. Sivula, Adv. Energy Mater. 2018, 1802585.[2] P. Bornoz, M. S. Prévot, X. Yu, N. Guijarro, K. Sivula, J. Am. Chem. Soc. 2015, 137, 15338.

Realization of ultrathin red 2D carbon nitride sheets to significantly boost the photoelectrochemical water splitting performance of TiO2 photoanodes

Ultrathin 2D carbon nitride sheets (CNs) are potential materials for solar energy conversion. However, these ultrathin sheets usually suffer from a wider bandgap of 3.06 eV, and thus nothing but ultraviolet range absorption. Here, we realized that red CNs has a narrower bandgap of 2.05 eV with a strong band-to-band visible-light absorption band by fluorination of atomic CNs followed by thermal defluorination (F-DF). Theoretical calculation results indicate that (i) a defect band arises near the conduction band minimum (CBM) after F-DF, resulting in a downward shift of the CBM, and (ii) the band structures are highly associated with the spatial distribution of defects in ultrathin 2D CNs. Furthermore, we confirm that such visible-light absorption band of red CNs can enable the number of photons to harvest a larger portion of solar spectrum, and suppress the rapid recombination of the photogenerated carriers. Consequently, the red CNs-sensitized TiO2 nanorod-based photoanode exhibits an outstanding photoelectrochemical water splitting activity in the visible light range. This work presents a new strategy for using 2D wide-bandgap material of bandgap narrowed to achieve a strong band-to-band visible-light absorption band.

Unravelling a long-lived ligand-to-metal cluster charge transfer state in Ce-TCPP metal organic frameworks.

Metal organic frameworks (MOFs) have emerged as promising photocatalytic materials for solar energy conversion. However, a fundamental understanding of light harvesting and charge separation (CS) dynamics in MOFs remains underexplored, yet they are key factors that determine the efficiency of photocatalysis. Herein, we report the design and CS dynamics of the Ce-TCPP MOF using ultrafast spectroscopic methods.

High-Temperature Solar Thermal Energy Conversion Enhanced by Spectrally-Selective Metafilm Absorber under Concentrated Solar Irradiation

Concentrating solar power, particularly parabolic trough system with solar concentrations less than 50, requires spectrally selective solar absorbers that are thermally stable at high temperatures of 400degC above to achieve high efficiency. In this work, the solar-thermal performance of a selective multilayer metafilm absorber is characterized along with a black absorber for comparison by a lab-scale experimental setup that measures the steady-state absorber temperature under multiple solar concentrations. Heat transfer analysis is employed to elucidate different heat transfer modes and validate the solar-thermal experiment. Due to the superior spectral selectivity and excellent thermal stability, the metafilm absorber deposited on the cost-effective stainless steel foil could achieve the solar-thermal efficiency 57% at a steady-state temperature of 371degC under 10 suns during the lab-scale experiment with losses, while a highest efficiency of 83% was projected under the same conditions for practical solar thermal applications. The results here will facilitate the research and development of novel solar materials for high-efficiency solar thermal energy conversion.

Anisotropic CuInSe2 nanocrystals: synthesis, optical properties and their effect on photoelectric response of dye-sensitized solar cell

CuInSe2 I–III–VI2 ternary semiconductor considered as one of the most promising semiconductor material which considers a very efficient solar energy conversion material. An organometallic pyrolysis method is used to prepare monodisperse CuInSe2 nanoparticles using a mixture of oleylamine, and trioctylphosphine (TOP) as capping materials. Controlling the particle shape dot, rods or flowers occurs via varying the reaction temperatures (160, 200, 220°C) respectively. The obtained particles have been characterized to determine the shape and size of CuInSe2 nanoparticles using HR-TEM and XRD. The optical and the electronic properties of these particles have been investigated and discussed in details. Then the different shapes of CIS nanoparticles (nanodots, nanorods, and nanoflowers) were introduced to the DSSC to study their effect on the optical switching properties. It was found that the nanoflowers provide better photovoltaic performance than the other shapes; since it reduces the settling time to 50 milliseconds after it was more than 17 second before adding CIS nanoparticles to the cells.

Electrostatic adsorption of a fluorophores-modified light-harvesting complex II on TiO2 photoanodes enhances photovoltaic performance

The major light-harvesting complex of photosystem II, or LHCII, has been utilized in photovoltaic applications because of its high pigment density. In vitro assembled recombinant LHCII is a modifiable biomimetic material for solar energy conversion. In this report, we assemble a modified recombinant LHCII from apoproteins covalently conjugated artificial fluorophores Atto 590 which absorb greatly near visible green region, where LHCII possesses relatively weak absorption. The absorption and fluorescence excitation spectra indicate that the modified recombinant LHCII possesses enhanced light harvesting capacity because Atto 590 molecules efficiently transfer energy to LHCII. The unmodified or modified recombinant LHCII is then adsorbed on the TiO2 electrode respectively to construct sensitized solar cells, both of which present remarkable photovoltaic enhancement. The incident photon-to-electron conversion efficiency measurements confirm the contribution of the artificial fluorophores. The modified recombinant LHCII sensitized solar cell presents 9.1% increase in open circuit voltage and 13.6% increase in short-circuit current density, compared to the unmodified one. These results suggest that modifications of the recombinant LHCII are feasible ways to enhance its performance in biophotovoltaic cells.

MXene aerogel-based phase change materials toward solar energy conversion

Two-dimensional transition-metal carbides/carbonitrides (MXenes) have demonstrated wide application prospect in energy conversion and storage, mostly in the form of electrochemical energy storage. Compared with the conversion between chemical energy and electrical energy, an energy conversion process initiated by solar energy and driven by the physical change of energy materials will be a sustainable and environmentally friendly strategy. Therefore, a high-performance MXene aerogel-based phase change material for solar energy conversion and thermal energy storage is constructed. MXene nanosheets with an extinction coefficient of 25.67 L/(g.cm) at 808 nm demonstrate excellent light absorption performance, which can spontaneously convert the solar energy into thermal energy. The polyethylene glycol (PEG) possessing high affinity with MXene acts the medium for thermal energy storage and release in the process of fusion and solidification. The MXene@PEG aerogels are lightweight, with a density about 30 mg/cm3. The MXene skeleton is introduced as supporting materials to keep the shape of MXene@PEG aerogel stable during the phase change process. The MXene nanosheets improve the thermal stability of PEG, the thermal decomposition temperatures can be increased by 40 °C. The actual fusion and solidification enthalpies of MXene@PEG aerogels can reach 167.72 and 141.51 J/g, respectively. The photothermal storage efficiency of MXene@PEG aerogels reaches a relatively high value of 92.5%. This work provides a new type of scaffold for lightweight and shape-stable photothermal carrier and paves the way for the application of non-graphene 2D materials toward solar energy utilization.

Solar Thermal Energy Conversion Enhanced by Selective Metafilm Absorber Under Multiple Solar Concentrations at High Temperatures

Concentrating solar power, particularly parabolic trough system with solar concentrations less than 50, requires spectrally selective solar absorbers that are thermally stable at high temperatures of 400°C above to achieve high efficiency. In this work, the solar-thermal performance of a selective multilayer metafilm absorber is characterized along with a black absorber for comparison by a lab-scale experimental setup that measures the steady-state absorber temperature under multiple solar concentrations. Heat transfer analysis is employed to elucidate different heat transfer modes and validate the solar-thermal experiment. Due to the superior spectral selectivity and excellent thermal stability, the metafilm absorber deposited on the cost-effective stainless steel foil could achieve the solar-thermal efficiency 57% at a steady-state temperature of 371°C under 10 suns during the lab-scale experiment with losses, while a highest efficiency of 83% was projected under the same conditions for practical solar thermal applications. The results here will facilitate the research and development of novel solar materials for high-efficiency solar thermal energy conversion.

Highly Selective CO2 Capture and Its Direct Photochemical Conversion on Ordered 2D/1D Heterojunctions

Summary Polymeric carbon nitrides (CNs) are regarded as the most sustainable materials for solar energy conversion via photocatalytic processes. However, the first-generation CNs suffered from imperfect charge separation and insufficient CO2 adsorption. Herein, the construction of a heterojunction material involving highly crystalline CN-nanorods with ordered alignment on graphene is delineated, which improves light harvesting, CO2 capture, and interface charge transfer. The graphene-supported 1D nano-arrays of crystalline CNs show a comparably high selectivity of CO2/N2 up to 44, with an isosteric heat of adsorption of 55.2 kJ/mol for CO2. The heterojunction material also drives the simple and efficient CO2 photoreduction in the gas phase, without the addition of any cocatalyst or sacrificial agent, even at the more relevant case of low concentrations of CO2. These findings provide a robust way for tailoring the performance of CN materials, with the aim of a practicable technological application for CO2 capture and photoreduction.

Performance Investigation of Mott-Insulator LaVO3 as a Photovoltaic Absorber Material

Mott insulators have recently been identified as potential solar energy conversion material due to their favorable parameters. In this paper, we have investigated the cell performance by exploring the photovoltaic properties of Mott Insulator LaVO3 (LVO). The LVO thin films were grown by the sol–gel technique followed by a sintering pathway under various processing conditions. We investigated the influence of processing parameters on the structural, optical and electrical properties of the films through different characterization techniques. A correlation between the material parameters with the device performance has been established to ensure LVO perovskite for photovoltaic applications. This analysis will aid researchers to realize Mott insulators as light absorber material.

Mo Thio Molecular Complexes As Water-Soluble Catalysts for the Photocatalytic Hydrogen Evolution Reaction on 2D Materials

Producing hydrogen fuel through solar-driven photoelectrochemical (PEC) water splitting represents an attractive approach for the development of sustainable energy. 2D semiconducting Transition Metal dichalcogenide (TMDC) nanosheets are attractive materials for solar energy conversion and have been applied as photocathodes for the Hydrogen Evolution Reaction (HER). To improve the performances of the photocathodes, optimized TMDC film microstructure was proposed involving a self-assembly at a liquid-liquid interface. In addition, in combination with a hexyl-tri-silane surfactant treatment, molecularly thin 2D WSe2 nanosheets films were coated by a Pt-Cu catalyst. In this process, the increase of photocurrent resulting from the surfactant treatment was attributed to edge site passivation of the 2D nanosheets drastically decreasing the charge carrier recombination site density. Indeed, for a large scale development of these photocathodes, replacement of Pt-Cu by a precious metal-free catalyst is highly desirable. In this talk, we will present our recent results concerning Mo thio complexes as catalysts anchored on WSe2 nanosheets for efficient water splitting under visible light irradiation. We used WSe2 films prepared by a simple film forming process, i.e. drop casting, and an aqueous environmentally friendly process for the catalyst preparation. Active molecular Mo catalysts including (Mo2S12)2- were deposited via a selection process from a solution allowing the deposition of the most interactive Mo complexes towards the WSe2 nanosheets thus improving their anchorage and durability. Our ultrathin films showed a current density up to -2 mA/cm² at 0 V vs NHE without any passivation additive such as HTS surfactant. The respective contributions namely in electro-catalysis and site passivation observed experimentally for the various molecular Mo complexes involved were supported by DFT calculations of i) Adsorption energies of the Mo thio complexes on the WSe2 substrates and ii) Free energies changes for the hydrogen Evolution Reaction on the various adsorbed molecular Mo complexes. These results will greatly help to better design molecular photo-catalysts for photo-electrodes displaying high surface recombination site density.

(Invited) Toward Unity Quantum Efficiency for Plasmon Induced Hot Electron Transfer at Metal/Semiconductor Junctions

It has been well-established that excitation of plasmons in metal nanostructures can lead to the injection of hot electrons into semiconductors or adsorbed molecules, which can be used to enhance photocatalysis. This novel mechanism suggests that plasmonic nanostructures can potentially function as a new class of widely tunable and robust light harvesting and catalytic materials for solar energy conversion. More importantly, it provides a novel approach to access highly energetic and reactive states of metals that is difficult to access with thermal chemistry. However, plasmon-induced hot electron injections from metal to semiconductor or molecules are still inefficient because of unfavorable initial hot electron distribution and the competing ultrafast hot electron relaxation processes within the metallic domain. In this talk, we discuss two approaches to enhance the efficiency of plasmon induced hot electron transfer. In the first approach, we explore the possibility of enhancing hot electron distribution by decreasing the size of plasmonic Au particles. Using CdS/Au nanorod heterostuctures, we show that the hot electron injection efficiency increases at smaller Au particle size. We attribute this size dependence to increasing contribution of surface assisted plasmon damping, which generates more hot electrons compared to damping by interband transition. In the second approach, we demonstrate that in CdSe/Au hetersostructureswith strong metal/semiconductor coupling, the plasmon decays by direct excitation of an electron from the metal to semiconductor, i.e. plasmon induced interfacial charge transfer transition (PICTT). The new plasmon damping pathway can be very efficient because it bypasses the competition with hot electron relaxation within the metal satisfies both the energy and momentum conservation. We will discuss whether PICTT is a general scheme for efficient hot electron transfer and present preliminary findings of highly efficient plasmon induced hot electron transfer at plasmonic metal/oxide semiconductor interfaces.

Non-fullerene Acceptors for Harvesting Excitons from Semiconducting Carbon Nanotubes

Semiconducting single-walled carbon nanotubes (s-SWCNTs) are promising materials for solar energy conversion and photodetectors. Fullerenes and their derivatives, being widely employed as electron ...

Remarkable Visible-Light Photocatalytic Activity Enhancement over Au/p-type TiO2 Promoted by Efficient Interfacial Charge Transfer.

Metal-induced photocatalysis has emerged as a promising approach for exploiting visible-light-responsive composite materials for solar energy conversion, which is generally hindered by low photocatalytic efficiency. Herein, for the first time, an Au/p-TiO2 (p-type TiO2) strategy with the hole transfer mechanism is developed, remarkably promoting visible-light photocatalytic performance. An efficient acetone evolution rate (138 μmol·g-1·h-1) in the photocatalytic isopropyl alcohol (IPA) degradation under λex = 500 nm light (light intensity, 5.5 mW/cm2) was achieved over Au/p-TiO2, which is approximately 5 times as high as that over Au/n-TiO2 under the same conditions. Photoluminescence and electrochemical impedance spectroscopy measurements indicate enhanced charge carrier separation and transfer for Au/p-TiO2. In an elaborate study, apparent quantum efficiency and transmission electron microscopy characterization on selective PbO2 deposition over p-TiO2 revealed that visible-light-excited holes other than electrons generated in the Au interband transition transferred to p-TiO2, which is opposite to the general route in Au/n-TiO2 (n-type TiO2). Energetic holes generated in the d band of Au led to a fluent transfer across the Schottky barrier, which is further confirmed by the IPA photodegradation mechanism study with different scavengers over Au/p-TiO2. This discovery opens up new opportunities in designing and developing efficient metal semiconductor composite materials with visible-light response.