Dye-sensitized Photoelectrochemical Cells Research Articles

BODIPY Chemisorbed on SnO2 and TiO2 Surfaces for Photoelectrochemical Applications.

Advancement toward dye-sensitized photoelectrochemical cells to produce solar fuels by solar-driven water splitting requires a photosensitizer that is firmly attached to the semiconducting photoelectrodes. Covalent binding enhances the efficiency of electron injection from the photoexcited dye into the metal oxide. Optimization of charge transfer, efficient electron injection, and minimal electron-hole recombination are mandatory for achieving high efficiencies. Here, a BODIPY-based dye exploiting a novel surface-anchoring mode via boron is compared to a similar dye bound by a traditional carboxylic acid anchoring group. Through terahertz and transient absorption spectroscopic studies, along with interfacial electron transfer simulations, we find that, when compared to the traditional carboxylic acid anchoring group, electron injection of boron-bound BODIPY is faster into both TiO2 and SnO2. Although the surface coverage is low compared with carboxylic acids, the binding stability is improved over a wide range of pH. Subsequent photoelectrochemical studies using a sacrificial electron donor showed that this combined dye and anchoring group maintained photocurrent with good stability over long-time irradiation. This recently discovered binding mode of BODIPY shows excellent electron injection and good stability over time, making it promising for future investigations.

Increased solar-driven chemical transformations through surface-induced benzoperylene aggregation in dye-sensitized photoanodes

The impact of benzo[ghi]perylenetriimide (BPTI) dye aggregation on the performance of photoelectrochemical devices was explored, through imide-substitution with either alkyl (BPTI-A, 2-ethylpropyl) or bulky aryl (BPTI-B, 2,6-diisopropylphenyl) moieties, to, respectively, enable or suppress aggregation. While both dyes demonstrated similar monomeric optoelectronic properties in solution, adsorption onto mesoporous SnO2 revealed different behavior, with BPTI-A forming aggregates via π-stacking and BPTI-B demonstrating reduced aggregation in the solid state. BPTI photoanodes were tested in dye-sensitized solar cells (DSSCs) before application to dye-sensitized photoelectrochemical cells (DSPECs) for Br2 production (a strong oxidant) coupled to H2 generation (a solar fuel). BPTI-A demonstrated a twofold higher dye loading of the SnO2 surface than BPTI-B, resulting in a fivefold enhancement to both photocurrent and Br2 production. The enhanced output of the photoelectrochemical systems (with respect to dye loading) was attributed to both J- and H- aggregation phenomena in BPTI-A photoanodes that lead to improved light harvesting. Our investigation provides a strategy to exploit self-assembly via aggregation to improve molecular light-harvesting and charge separation properties that can be directly applied to dye-sensitized photoelectrochemical devices.Graphical Increased Solar-Driven Chemical Transformations through Surface-Induced Benzoperylene Aggregation in Dye-Sensitized Photoanodes. Benzo[ghi]perylenetriimide (BPTI) dyes are investigated to reveal the effect of aggregation by π-stacking on photovoltaic parameters in dye-sensitized devices. Photoanodes with aggregating BPTIs show both J- and H- aggregation phenomena leading to enlarged visible light absorbance and increased electron injection. The use of aggregating BPTI outperforms a non-aggregation BPTI with fivefold in terms of photocurrent and product generation.

Metal Complexes for Dye-Sensitized Photoelectrochemical Cells (DSPECs).

Since Mallouk's earliest contribution, dye-sensitized photoelectrochemical cells (DSPECs) have emerged as a promising class of photoelectrochemical devices capable of storing solar light into chemical bonds. This review primarily focuses on metal complexes outlining stabilization strategies and applications. The ubiquity and safety of water have made its splitting an extensively studied reaction; here, we present some examples from the outset to recent advancements. Additionally, alternative oxidative pathways like HX splitting and organic reactions mediated by a redox shuttle are discussed.

A dye sensitized photosynthesis cell for stable water oxidation mediated by photo-generated bromine.

The critical step of a dye-sensitized photoelectrochemical cell (DSPEC) is water oxidation. The photoanodes suffer rapid surface carrier recombination due to slow water oxidation kinetics and this results in low solar conversion efficiency and poor stability. Here, we design a novel sensitization-oxidation photo-anode, where the [Ru(4,4'-PO3H2-bpy)(bpy)2]2+ (RuP2+, bpy = 2,2'-bipyridine) chromophore and [Ru(bda)(pic)2] (pic = picoline, bda = 2,2'-bipyridine-6,6'-dicarboxylate) water oxidation catalyst (WOC) are immobilized separately on the surface of a mesoporous semiconductor thin film. The electrode creates a mobile and strong Br3- oxidant generated by the dye-sensitized electrode, which initiates water oxidation at a remote catalytic site. Under 100 mW cm-2 illumination in pH 4.65 in 0.1 M acetate buffer solution, the photoanode could perform a stable photoelectrochemical water oxidation for 6 hours with a photocurrent density of around 0.25 mA cm-2. This dual electrode could open a new door by utilizing an electron transfer mediator to design highly stable photoelectrochemical cells.

(Invited) C–C Bond Cleavage of Lignin with an Organic Dye-Sensitized Photoanode

Chemoselective C–C bond cleavage remains a challenge for the degradation of polymers because of the relatively high bond dissociation energy of C–C σ-bonds at room temperature. Organic molecular-based dye-sensitized photoelectrochemical cells (DSPECs) could offer a means of using renewable solar energy to drive energetically demanding chemoselective C–C bond cleavage reaction. This study reports the solar light-driven activation of a bicyclic aminoxyl mediator to achieve C–C bond cleavage in the aryl-ether linkage of a lignin model compound (LMC) at room temperature using a donor–π-conjugated bridge–acceptor (D–π–A) organic dye-based DSPEC system. The 5-[4-(diphenylamino)phenyl]thiophene-2-cyanoacrylic acid (DPTC) D–π–A organic dye was investigated along with a bicyclic aminoxyl radical mediator (9-azabicyclo[3,3,1]nonan-3-one-9-oxyl, KABNO) in solution and at the interface of a mesoporous structured TiO2 substrate in the presence of LMC. Photophysical studies of DPTC with KABNO were carried out to show intermolecular energy/electron transfer under 1 sun illumination (100 mW·cm− 2). The D–π–A type DPTC sensitized mesoporous TiO2 photoanode in the presence of KABNO can facilitate the generation of the reactive oxoammonium species KABNO+ as a strong oxidizing agent, which plays an important role in the photocatalytic oxidative C–C bond cleavage of LMC. The photoelectrochemical oxidative reaction in a complete DSPEC with KABNO afforded the chemoselective C–C bond cleavage products 2-(2-methoxyphenoxy)acrylaldehyde (94%) and 2,6-dimethoxy-1,4-benzoquinone (66%). This process provides a first report utilizing a D–π–A type organic dye in combination with a bicyclic nitroxyl radical mediator for heterogeneous photoelectrolytic oxidative cleavage of C–C σ-bonds, modeled on those found in lignin, at room temperature.

(Invited) Limitation of Molecular Twisting: Upgrading a Donor-Acceptor Dye to Drive H2 Evolution

Dye-sensitized photoelectrochemical cells (DSPECs) have attracted wide attention to convert solar energy into high-energy chemicals. A DSPEC consists of a photoanode performing the oxidation half reaction and aphotocathode performing the reduction half reaction. In this presentation I will demonstrate how the performance of a dye-sensitized photocathode can be manipulated to enhance performance and even produce hydrogen! We have used a state- of-the-art dye (D-A P1 dye) on the surface of optimized NiO, and co-adsorbed myristic acid (Tetradecanoic Acid), which has a carboxyl anchoring group and a long apolar alkyl chain. Time-resolved photoluminescence and Density Functional Theory studies show that twisting lowers the energy levels of the photoexcited D-A dye, while twisting is inhibited in case myristic acid is co-adsorbed on the NiO surface. The presence of myristic acid also favors light-induced charge separation, as apparent from femtosecond transient absorption, and increases the apparent photocurrent. Very interestingly, only in the presence of myristic acid, light-induced H2 evolution is observed in aqueous media, despite the absence of a H2 evolution catalyst. We assign the H2 generation to a synergetic effect of inhibited twisting of the D-A dye radical anion increasing its electrochemical potential, combined with charge transfer and conversion of H+ on the hydroxylated NiO surface. Our work illustrates the importance of understanding effects of photoinduced intramolecular twisting and demonstrates that control thereof offers a simple design approach for efficient solar fuel devices.

A computational study photophysical properties of a series phenothiazine-linked-BODIPY as D-D-π-a photosensitizer unit for photo-induced hydrogen production from water

Phenothiazine-derivatives are designed as sensitizers which covalently-linked with BODIPY for application in a system of dye-sensitized photoelectrochemical cells (DSPECs). A series of phenothiazine-linked-BODIPY as D-D-π-A chromophore have been investigated by a computational approach for studying the capability of the photosensitizers for application in photoinduced water splitting hydrogen production in DSPECs. The geometries of sensitizers at the ground state and excited state were optimized by the CAM-B3LYP/6-31G (d,p) level method. The theoretical study has been done in order to investigate the photophysical properties such as absorption profile, HOMO-LUMO energy and surface plots of the photosensitizer. The result of calculation for HOMO-LUMO energy level of each dyes showed that the LUMO energy are ranging more than -2.8 - (-2.86) eV which is higher than -4.0 eV of conduction band of TiO2 as semiconductor in DSPEC, meaning that all these dyes could be used as photosensitizers in DSPECs. In addition, the oscillator strength data of each dyes showed the dyes have absorption profile in visible region, meaning the dyes could harvest higher intensity of sunlight to induce water splitting reaction to produce hydrogen.

(Invited) Nitroxyl-Derivatives As Cocatalyst for Lignin Decomposition by Dye-Sensitized Photoelectrochemical Cell

For stable and chemoselective decomposition of lignin model compound by DSPEC, metal based sensitizer was replaced by organic dye, 5-[4-(diphenylamino)phenyl]thiophene-2-cyanoacrylic acid (L1). For effective regeneration of dyes and oxidation of lignin model compounds(LMCs), bicyclic nitroxyl derivates, such as 2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) and 9-azabicyclo[3,3,1]nonan-3-one-9-oxyl (Keto-ABNO) were used. Keto-ABNO exhibited higher photo-electrocatalytic activity than TEMPO for the oxidation and decomposition of LMC. The superior reactivity with high selectivity of L1 sensitizer with Keto-ABNO mediator is attributed to the effective Caryl-Cα bond cleavage with 100% conversion yield for 24hrs at room temperature while it was 86% with TEMPO. The D–π–A type organic dye with a bicyclic nitroxyl radical mediator provides a possible strategic pathway for heterogeneous photocatalytic C–C bond cleavage at ambient condition.

Charge Recombination Deceleration by Lateral Transfer of Electrons in Dye-Sensitized NiO Photocathode.

Control of charge separation and recombination is critical for dye-sensitized solar cells and photoelectrochemical cells, and for p-type cells, the latter process limits their photovoltaic performance. We speculated that the lateral electron hopping between dyes on a p-type semiconductor surface can effectively separate electrons and holes in space and retard recombination. Thus, device designs where lateral electron hopping is promoted can lead to enhanced cell performance. Herein, we present an indirect proof by involving a second dye to monitor the effect of electron hopping after hole injection into the semiconductor. In mesoporous NiO films sensitized with peryleneimide (PMI) or naphthalene diimide (NDI) dyes, dye excitation led to ultrafast hole injection into NiO from either excited PMI* (τ < 200 fs) or NDI* (τ = 1.2 ps). In cosensitized films, surface electron transfer from PMI- to NDI was rapid (τ = 24 ps). Interestingly, the subsequent charge recombination (ps-μs) with NiO holes was much slower when NDI- was generated by electron transfer from PMI- than when NDI was excited directly. We therefore indicate that the charge recombination is slowed down after the charge hopping from the original PMI sites to the NDI sites. The experimental results supported our hypothesis and revealed important information on the charge carrier kinetics for the dye-sensitized NiO photoelectrode system.

Artificial photosynthesis a brief literature review

Dye Sensitized Photoelectrochemical Cells (DS-PEC) are a promising development for artificial photosynthesis. Currently however photoinduced conversion of water to hydrogen and oxygen remains limited by desorption, alternative processes and charge accumulation. This brief literature review will primarily focus on transition metal complex chromophore catalyst dyads, for water oxidation catalysis (WOC) as well as hydrogen evolution catalysis (HEC). Assessing the dyads individual charge separation, electron transfer and catalytic photoelectrochemical properties. Comparing and contrasting the techniques employed by Dye Sensitized Photoelectrochemical Cells (DS-PEC) dyads in addition to collectively evaluating their current limiting factors and suggesting potential developments for further work.

Overcoming residual carbon-induced recombination in water-oxidation catalysis: combining a superior catalyst with low-carbon-content atomic layer deposition of SnO2 for improved catalysis

Two routes, as well as their combination, are examined for overcoming recombination in a dye-sensitized photoelectrochemical cell for water oxidation catalysis.

Strategies to Enhance the Rate of Proton‐Coupled Electron Transfer Reactions in Dye‐Water Oxidation Catalyst Complexes

AbstractA thorough understanding of the proton‐coupled electron transfer (PCET) steps that are involved in photocatalytic water oxidation is of crucial importance in order to increase the efficiency of dye‐sensitized photoelectrochemical cells (DS‐PEC) for solar to fuel conversion. This work provides a computational investigation of the ground and excited state potential energy surfaces of PCET reactions in two supramolecular dye‐catalyst complexes for photocatalytic water splitting. The intrinsic reaction coordinate path is computed for the rate limiting PCET step in the catalytic cycle for both complexes. By using time‐dependent density functional theory calculations, we show that the ground and excited state potential energy surfaces have a (near) degeneracy in the region of the PCET transition state. We discuss two possible strategies that take advantage of this feature to accelerate the PCET reaction: (i) through optimizing the conditions for vibronic coupling by chemical design and synthesis or (ii) through populating the product state with appropriately tuned laser pulses.

(Invited, Digital Presentation) Photocatalytic C-C/C-O Bond Cleavage in Lignin Using a Dye-Sensitized Photoelectrochemical Cell

Molecular-based dye-sensitized photoelectrochemical cells (DSPECs) have traditionally targeted solar-driven water splitting for the conversion of solar energy into fuels in aqueous media. Here we describe a novel approach to develop the DSPECs by combining hydrogen atom transfer mediator (HAT) with nanostructured semiconductors and photocatalysts for photocatalytic C−C/C−O bonds cleavage in lignin. This work reports the application of the DSPEC specifically designed to carry out photocatalytic oxidative cleavage of C−C/C−O σ-bonds in lignin model compounds at the photoanode. Current studies targeting the development of photocatalysts via HAT process for biomass conversion especially lignin depolymerization will be described, with the novel finding that a DSPEC utilizes a solar-driven catalytic conversion of woody biomass into value-added fuels and chemicals under aerobic mild conditions. The efficient photocatalytic bond cleavage in DSPECs is important to the development of sustainable approaches for lignin depolymerization and biomass conversion.

The Effect of Photoanode Interface and Surface Treatment in Dye-Sensitized Photo-Electrochemical Systems for Effective Lignin Decomposition

Traditionally, Dye-sensitized photo electrochemical cells (DSPECs) have been targeted for solar-driven water splitting as production of fuels in aqueous media. Recently, hydrogen atom transfer incorporated dye-sensitized photo electrochemical cell (HAT-DSPEC) which used photocatalyst and homogeneous catalysts incorporating system was suggested for the decomposition process of lignin. This HAT-DSPEC system representing conversion efficiencies over 90% resulted in the formation of the oxidized ketone product from model compounds under simulated solar illumination with an applied bias 0.4 V vs Ag/Ag+ for 24 hrs. However, they have several issues such as long reaction time, low stability, and high bias potential.To overcome these problems, in this study, dye-sensitized photovoltaics’ advanced technic is applied. In HAT-DSPEC system, photo-anode (TiO2@Dye) has important role to produce oxoammonium species by oxidizing nitroxyl derivatives, such as 4-acetomido TEMPO (ACT). And these oxoammonium species act as a catalytic reaction with lignin model compounds (LMCs) to oxidizing of 1o or 2o alcohol and cleavage Caryl-Cα bond cleavage. However, in photo-anode, lots of charge recombination and electron back transfer occurs on the FTO and TiO2 surface and it induce low current and reactivity. For effectively producing oxoammonium species from photoelectrode, using blocking layer to passivate FTO surface from electrolytes and applying TiCl4 post-treatment for fast charge transport in TiO2 by enhancing interconnection of TiO2 nanoparticles. The photocurrent response of the m-TiO2@Ru470 photoelectrode in a nonaqueous electrolyte was examined with increasing mediator concentration during light on/off cycles under AM 1.5G illumination (100 mW/cm2), with an applied bias 0.1 V vs Ag/Ag+. Three kinds of electrode condition such as m-TiO2, BL/m-TiO2, BL/m-TiO2/TiCl4 post treatment was examined under same condition and treated photoelectrode (BL/m-TiO2/TiCl4) showed a significant increase in maximum photocurrent up to approximately 367.69 μA/cm2 with 3 mM ACT mediator, while BL/m-TiO2 exhibits 26.75 μA/cm2 and m-TiO2 1.26 μA/cm2. This result indicates that the blocking layer and TiCl4 post treatment enhanced electron lifetime and collection efficiency in the photoelectrode, as well as enhancing the capability of producing oxoammonium species.

(Invited) Hydrogen Atom Transfer Coupled Dye-Sensitized Photoelectrochemical Cell for Lignin Decomposition

For the decomposition process of lignin, there have been several processes reported. However, low selectivity of oxidative cleavage is one of prime issues because of reaction under harsh condition such as high temperature and high pressure. To overcome these problems, especially, dye-sensitized photo-electrochemical cells (HAT-DSPEC), which used photocatalyst (RuC) and homogeneous catalysts incorporated system was suggested. it represents conversion efficiencies over 90% under 24 h light illumination (AM 1.5G). However, metal complex sensitizer has disadvantages like low stability, high cost and low absorption coefficient.In this study, for highly stable HAT-DSPEC process, metal based sensitizer was replaced by organic dye(5-[4-(diphenylamino)phenyl]thiophene-2-cyanoacrylic acid, L1) which has high stability and molar absorption coefficient. For regenerating dye molecules and oxidating lignin model compounds(LMCs), bicyclic nitroxyl derivates, such as 2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO), and 9-azabicyclo[3,3,1]nonan-3-one-9-oxyl (Keto-ABNO) was used. In HAT-ODSPEC (organic dye-sesitized photo-electrochemical cell), Keto-ABNO exhibits higher photo-electrocatalytic activity than TEMPO for the oxidation and decomposition of LMC. The superior activity of L1 sensitizer with Keto-ABNO mediator is especially noteworthy of Caryl-Cα bond cleavage and with keto-ABNO exhibits 100% conversion yield of for 24hrs at room temperature while 86% with TEMPO. This HAT-ODSPEC process provides a unique foundation to perform selective C−C bond cleavage for real lignin conversion technologies.

Copper(I) Donor–Chromophore–Acceptor Assembly for Light-Driven Oxidation on a Zinc Oxide Nanowire Electrode

Dye-sensitized photoelectrochemical cells have emerged as a potential candidate for solar-to-fuel conversion. Herein, we report a Cu(I)-based donor–chromophore–acceptor triad comprising a triphenylamine electron donor and a dipyrido[3,2-a:2′,3′-c]phenazine electron acceptor as the active material for photoanodes. Energy levels of this triad are carefully aligned for thermodynamically favorable photoinduced electron transfer. Once this triad is surface-grafted onto zinc oxide nanowires, photoelectrochemical studies confirm the utility of this architecture for oxidative processes such as alcohol oxidation with modest yields.

(Invited) Dye-Sensitized Photoelectrochemical Cells with Hydrogen-Atom Transfer Co-Catalyst for Oxidative Lignin Decomposition

The lack of selectivity of oxidative-cleavage is one of prime issues for decomposition of lignin, because of the harsh reaction environments, such as high temperature and high pressure, in general. Dye-sensitized photoelectrochemical cells with a homogenous hydrogen-atom transfer co-catalyst with Ruthenium-complex based sensitizer as a photocatalyst (e.g. RuC ((bis-2,2′-bipyridine)(2,2′-bipyridine-4,4′-dicarboxylic acid)Ru(II)) (HAT-DSPEC), was suggested as an alternative and this system exhibited the conversion efficiency of over 90% at 24 hour illumination (AM 1.5G) although these metal-complex based sensitizers, having relatively low values of absorption coefficient, generally are not cost-effective and stable enough.In this study, for highly stable HAT-DSPEC process, metal complex sensitizer was replaced by organic dye(5-[4-(diphenylamino)phenyl]thiophene-2-cyanoacrylic acid, L1) which has high stability and molar absorption coefficient. Also three kinds of organic nitroxyl mediators (HAT) was used such as 2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO), 4-Acetamido-TEMPO (ACT) and 9-azabicyclo[3,3,1]nonan-3-one-9-oxyl (Keto-ABNO). Each HATs (TEMPO, ACT and keto-ABNO) showed different reactivity and conversion efficiency (about 65%, 60% and 88%). In HAT-ODSPEC(organic dye-sesitized photo-electrochemical cell), Keto-ABNO showed highest conversion efficiency with 2-ol(S,G). This HAT-ODSPEC process provides a unique foundation to perform selective C−C bond cleavage for real lignin conversion technologies.

Photoanode Interface and Surface Treatment Effect in Dye-Sensitized Photo Electrochemical Systems on Oxidative Cleavage of Lignin

Traditionally, Dye-sensitized photo electrochemical cells (DSPECs) have been targeted for solar-driven water splitting as production of fuels in aqueous media. Recently, hydrogen atom transfer incorporated dye-sensitized photo electrochemical cell (HAT-DSPEC) which used photocatalyst and homogeneous catalysts incorporating system was suggested for the decomposition process of lignin. This HAT-DSPEC system representing conversion efficiencies over 90% resulted in the formation of the oxidized ketone product from model compounds under simulated solar illumination with an applied bias 0.4 V vs Ag/Ag+ for 24 hrs. However, they have several issues such as long reaction time, low stability and high bias potential.To overcome these problems, in this study, dye-sensitized photovoltaics’ advanced technic is applied. In HAT-DSPEC system, photo-anode (TiO2@Dye) has important role to produce oxoammonium species by oxidizing HAT mediator. And these oxidized HAT do a catalytic reaction with target materials: lignin model compounds (LMCs). However, in photo-anode, lots of charge recombination and electron back transfer occurs on the FTO and TiO2 surface. So, for effectively producing oxoammonium species from photoelectrode, using blocking layer to passivate FTO surface from electrolytes and applying TiCl4 post-treatment enhances charge transport in TiO2. The photocurrent response of the m-TiO2@Ru470 photoelectrode in a nonaqueous electrolyte was examined with increasing mediators concentration during light on/off cycles under AM 1.5G illumination (100 mW/cm−2), with an applied bias 0.4 V vs Ag/Ag+. Comparing three kinds of condition such as m-TiO2, BL/m-TiO2, BL/m-TiO2/TiCl4 post treatment, showed a significant increase in maximum photocurrent up to approximately 49.3, 101.3, 231.6 μA/cm−2 with 5 mM NHPI/2,6-Lutidine mediator. This result indicates that the blocking layer and TiCl4 post treatment enhanced electron life time and collection efficiency in the photoelectrode, as well as enhancing the capability of producing oxoammonium species.

In Silico Optimization of Charge Separating Dyes for Solar Energy Conversion.

Dye‐sensitized photoelectrochemical cells are promising devices in solar energy conversion. However, several limitations still have to be addressed, such as the major loss pathway through charge recombination at the dye‐semiconductor interface. Charge separating dyes constructed as push‐pull systems can increase the spatial separation of electron and hole, decreasing the recombination rate. Here, a family of dyes, consisting of polyphenylamine donors, fluorene bridges, and perylene monoimide acceptors, was investigated in silico using a combination of semi‐empirical nuclear dynamics and a quantum propagation of photoexcited electron and hole. To optimize the charge separation, several molecular design strategies were investigated, including modifying the donor molecule, increasing the π‐bridge length, and decoupling the molecular components through steric effects. The combination of a triphenylamine donor, using an extended 2‐fluorene π‐bridge, and decoupling the different components by steric hindrance from side groups resulted in a dye with significantly improved charge separation properties in comparison to the original supramolecular complex.

Aqueous Biphasic Dye‐Sensitized Photosynthesis Cells for TEMPO‐Based Oxidation of Glycerol

AbstractThis work reports an aqueous dye‐sensitized photoelectrochemical cell (DSPEC) capable of oxidizing glycerol (an archetypical biobased compound) coupled with H2 production. We employed a mesoporous TiO2 photoanode sensitized with the high potential thienopyrroledione‐based dye AP11, encased in an acetonitrile‐based redox‐gel that protects the photoanode from degradation by aqueous electrolytes. The use of the gel creates a biphasic system with an interface at the organic (gel) electrode and aqueous anolyte. Embedded in the acetonitrile gel is 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO), acting as both a redox‐mediator and a catalyst for oxidative transformations. Upon oxidation of TEMPO by the photoexcited dye, the in situ generated TEMPO+ shuttles through the gel to the acetonitrile–aqueous interface, where it acts as an oxidant for the selective conversion of glycerol to glyceraldehyde. The introduction of the redox‐gel layer affords a 10‐fold increase in the conversion of glycerol compared to the purely aqueous system. Our redox‐gel protected photoanode yielded a stable photocurrent over 48 hours of continuous operation, demonstrating that this DSPEC is compatible with alkaline aqueous reactions.