Photoelectrochemical Detection of Glucose by Using an Enzyme‐Modified Photoelectrode

A new photoelectrochemical method for the determination of glucose based on the photoelectrochemical effect of poly(thionine) photoelectrode to hydrogen peroxide (H₂O₂) was reported. The H₂O₂‐sensitive photoelectrode was fabricated by electropolymerizing thionine on the surface of ITO electrode. And then glucose oxidase was immobilized on the photoelectrode via the aid of chitosan enwrapping, forming an enzyme‐modified photoelectrode. The photoelectrode was employed as an electron acceptor; H₂O₂ from the catalytic reaction of enzyme was employed as an electron donor, developing an analytical method of glucose without hydrogen peroxidase. In the paper, the photoelectrochemical effects of photoelectrode to H₂O₂ and glucose were studied. The effects of the bias voltage and the electrolyte pH on the photocurrent were investigated. The linear response of glucose concentrations ranged from 0.05 to 2.00 mmol/L was obtained with a detection limit of 22.0 µmol/L and sensitivity of 73.2 nA/(mmol·L^?1). The applied feasibility of method was acknowledged through monitoring the glucose in practical samples.     

Performance of CeO2–TiO2-admixed photoelectrode for natural dye-sensitized solar cell

Extracts from roots of Beta vulgaris were used as natural sensitizers of a wide-bandgap semiconductor (CeO₂–TiO₂) in photoelectrochemical solar cells. The natural dye, adsorbed onto the semiconductor surface, absorbs visible light and promotes electron transfer across the dye/semiconductor interface. We have applied CeO₂–TiO₂ to natural dye sensitizer solar cells as a photoelectrode to reduce the charge recombination rate by providing energy barrier at the interface between the photoanode and electrolyte which offers an improvement of photovoltaic efficiency. Short-circuit current density (J _sc) and open-circuit voltages (V _oc) of 9.0 mA cm^?2 and 680 mV, respectively, were obtained, and an effective energy conversion efficiency of 3.5?% was achieved. This simple and cheap technique of cell preparation opens up a perspective of commercial feasibility for inexpensive and environment-friendly dye cells.     

Photoinduced Electron Transfer in Tetrathiafulvalene−Porphyrin−Fullerene Molecular Triads

The two molecular triads 1a and 1b consisting of a porphyrin (P) covalently linked to a fullerene (C₆₀) electron acceptor and tetrathiafulvalene (TTF) electron‐donor moiety were synthesized, and their photochemical properties were determined by transient absorption and emission techniques. Excitation of the free‐base‐porphyrin moiety of the TTF−P_{2 H}−C₆₀ triad 1a in tetrahydro‐2‐methylfuran solution yields the porphyrin first excited singlet state TTF−¹P_{2 H}−C₆₀, which undergoes photoinduced electron transfer with a time constant of 25 ps to give TTF−P_{2 H}^.+−C₆₀^.−. This intermediate charge‐separated state has a lifetime of 230 ps, decaying mainly by a charge‐shift reaction to yield a final state, TTF^.+−P_{2 H}−C₆₀^.−. The final state has a lifetime of 660 ns, is formed with an overall yield of 92%, and preserves ca. 1.0 eV of the 1.9 eV inherent in the porphyrin excited state. Similar behavior is observed for the zinc analog 1b . The TTF‐P_Zn^.+−C₆₀^.− state is formed by ultrafast electron transfer from the porphyrinatozinc excited singlet state with a time constant of 1.5 ps. The final TTF^.+−P_Zn−C₆₀^.− state is generated with a yield of 16%, and also has a lifetime of 660 ns. Although charge recombination to yield a triplet has been observed in related donor‐acceptor systems, the TTF^.+−P−C₆₀^.− states recombine to the ground state, because the molecule lacks low‐energy triplet states. This structural feature leads to a longer lifetime for the final charge‐separated state, during which the stored energy could be harvested for solar‐energy conversion or molecular optoelectronic applications.     

Photoinduced Oxygen Reduction Reaction Boosts the Output Voltage of a Zinc–Air Battery

Utilization of solar energy is of great interest for a sustainable society, and its conversion into electricity in a compact battery is challenging. Herein, a zinc–air battery with the polymer semiconductor polytrithiophene (pTTh) as the cathode is reported for direct conversion of photoenergy into electric energy. Upon irradiation, photoelectrons are generated in the conduction band (CB) of pTTh and then injected into the π_2p* orbitals of O₂ for its reduction to HO₂^?, which is disproportionated to OH^? and drives the oxidation of Zn to ZnO at the anode. The discharge voltage was significantly increased to 1.78 V without decay during discharge–charge cycles over 64 h, which corresponds to an energy density increase of 29.0 % as compared to 1.38 V for a zinc–air battery with state‐of‐the‐art Pt/C. The zinc–air battery with an intrinsically different reaction scheme for simultaneous conversion of chemical and photoenergy into electric energy opens a new pathway for utilization of solar energy.     

Nanostructured CuO/SrTiO3 bilayered thin films for photoelectrochemical water splitting

Bilayered thin films of CuO/SrTiO₃ with varying thickness of CuO were deposited by sol–gel spin-coating technique on indium tin oxide substrate and used as photoelectrode in the photoelectrochemical cell for water splitting reaction. Maximum photocurrent density of 1.85 mA/cm² at ?0.9 V/saturated calomel electrode was exhibited by 590-nm-thick CuO/SrTiO₃ bilayered photoelectrode, which is approximately eight times higher than that for CuO and 30 times higher than that for SrTiO₃. The bilayered system offered increased photocurrent density and enhanced photoconversion efficiency, attributed to improved conductivity, which ameliorate separation of the photo-generated carriers at the CuO/SrTiO₃ interface and higher value of flatband potential. Details about synthesis and various characterisations involving X-ray diffraction and scanning electron microscopy have been discussed. An energy band diagram has been proposed to dwell upon the mechanism of charge carrier transfer across the interface.     

Coupled Solar Battery with 6.9 % Efficiency

Solar-to-electrochemical energy storage in solar batteries is an important solar utilization technology comparable to solar-to-electricity (solar cells) and solar-to-fuel (photocatalytic cells) conversion. Unlike the indirect approach of integrated solar flow batteries combining photoelectrodes with redox-electrodes, coupled solar batteries enable direct solar energy storage, but are hampered by low efficiency due to rapid charge recombination of materials and misaligned energy levels between electrodes. Herein, we propose a design for a coupled solar battery that intercouples two photo-coupled ion transfer (PCIT) reactions through electron-ion transfer upon co-photo-pumping of photoelectrochemical storage cathode and anode. We used a representative covalent organic framework (COF) to achieve efficient charge separation and directional charge transfer between two band-matched photoelectrochemical storage electrodes, with a photovoltage sufficient for COF dual-redox reactions. By pumping these electrodes, the coupled solar battery stores solar energy via two synergistic PCIT reactions of electron-proton-relayed COF oxidation and reduction, and the stored solar energy is released as electrochemical energy during COF regeneration in discharge while interlocking the loops. A breakthrough in efficiency (6.9 %) was achieved, adaptive to a large-area (56 cm²) tandem device. The presented photo-intercoupled electron-ion transfer (PIEIT) mechanism provides expandable paths toward practical solar-to-electrochemical energy storage.     

A Cation‐Exchange Approach for the Fabrication of Efficient Methylammonium Tin Iodide Perovskite Solar Cells

Tin‐based halide perovskite materials have been successfully employed in lead‐free perovskite solar cells, but the overall power conversion efficiencies (PCEs) have been limited by the high carrier concentration from the facile oxidation of Sn²⁺ to Sn⁴⁺. Now a chemical route is developed for fabrication of high‐quality methylammonium tin iodide perovskite (MASnI₃) films: hydrazinium tin iodide (HASnI₃) perovskite film is first solution‐deposited using presursors hydrazinium iodide (HAI) and tin iodide (SnI₂), and then transformed into MASnI₃ via a cation displacement approach. With the two‐step process, a dense and uniform MASnI₃ film is obtained with large grain sizes and high crystallization. Detrimental oxidation is suppressed by the hydrazine released from the film during the transformation. With the MASnI₃ as light harvester, mesoporous perovskite solar cells were prepared, and a maximum power conversion efficiency (PCE) of 7.13 % is delivered with good reproducibility.     

Efficient and Stable MoS2/CdSe/NiO Photocathode for Photoelectrochemical Hydrogen Generation from Water

A novel CdSe/NiO heteroarchitecture was designed, prepared, and used as a photocathode for hydrogen generation from water. The composite films were structurally, optically, and photoelectrochemically characterized. The deposition of CdSe on the NiO film enhanced light harvesting in the visible‐light region and photoelectrochemical properties. Moreover, the CdSe/NiO photoelectrode showed superior stability both in nitrogen‐saturated and air‐saturated neutral environments. The CdSe/NiO photoelectrode after MoS₂ modification retained the stability of the CdSe/NiO electrode and exhibited higher photocatalytic and photoelectrochemical performances than the unmodified CdSe/NiO electrode. In pH 6 buffer solution, an average hydrogen‐evolution rate of 0.52 μmol h^?1 cm^?2 at ?0.131 V (versus reversible hydrogen electrode, RHE) was achieved on a MoS₂/CdSe/NiO photocathode, with almost 100 % faradaic efficiency.     

光电化学分解水电池的电极性能提高方法及光阴极研究进展

光电化学水分解电池能够将太阳能直接转化为氢能,是一种理想的太阳能利用方式. p-n叠层电池具有理论转换效率高、成本低廉、材料选择灵活等优势,被认为是最有潜力的一类光电化学水分解电池. 然而,目前这类叠层电池的太阳能转化效率还不高,主要原因是单个电极的效率太低. 本文介绍了几种提高光电极分解水性能的方法--减小光生载流子的体相复合、表面复合以及抑制背反应等,同时综述了国内外关于几种p型半导体光阴极的研究进展,如Si、InP、CuIn_1-x GaxS(Se)₂、Cu₂ZnSnS₄等. 通过总结,作者提出一种p-Cu₂ZnSnS₄(CuIn_1-xGaxS(Se)₂)/n-Ta₃N₅(Fe₂O₃) 组装方式,有望获得高效低成本叠层光电化学水分解电池.     

Photoelectrochemical Reduction of Carbon Dioxide to Methanol through a Highly Efficient Enzyme Cascade

Natural photosynthesis is an effective route for the clean and sustainable conversion of CO₂ into high‐energy chemicals. Inspired by the natural process, a tandem photoelectrochemical (PEC) cell with an integrated enzyme‐cascade (TPIEC) system was designed, which transfers photogenerated electrons to a multienzyme cascade for the biocatalyzed reduction of CO₂ to methanol. A hematite photoanode and a bismuth ferrite photocathode were applied to fabricate the iron oxide based tandem PEC cell for visible‐light‐assisted regeneration of the nicotinamide cofactor (NADH). The cell utilized water as an electron donor and spontaneously regenerated NADH. To complete the TPIEC system, a superior three‐dehydrogenase cascade system was employed in the cathodic part of the PEC cell. Under applied bias, the TPIEC system achieved a high methanol conversion output of 220 μm h⁻¹, 1280 μmol g⁻¹ h⁻¹ using readily available solar energy and water.     

Bulk heterojunction perovskite solar cells incorporated with solution-processed TiOx nanoparticles as the electron acceptors

In the past ten years, perovskite solar cells were rapidly developed, but the intrinsic unbalanced charge carrier diffusion lengths within perovskite materials were not fully addressed by either a planar heterojunction or meso-superstructured perovskite solar cells. In this study, we report bulk heterojunction perovskite solar cells, where perovskite materials CH₃NH₃PbI₃ is blended with solution-processed n-type TiO_x nanoparticles as the photoactive layer. Studies indicate that one-step solution-processed CH₃NH₃PbI₃:TiO_x bulk-heterojunction thin film possesses enhanced and balanced charge carrier mobilities, superior film morphology with enlarged crystal sizes, and suppressed trap-induced charge recombination. Thus, bulk heterojunction perovskite solar cells by CH₃NH₃PbI₃ mixed with 5 wt% of TiO_x, which is processed by one-step method rather than typical two-step method, show a short-circuit current density of 20.93 mA/cm², an open-circuit voltage of 0.90 V, a fill factor of 80% and with a corresponding power conversion efficiency of 14.91%, which is more than 30% enhancement as compared with that of perovskite solar cells with a planar heterojunction device structure. Moreover, bulk heterojunction perovskite solar cells possess enhanced device stability. All these results demonstrate that perovskite solar cells with a bulk heterojunction device structure are one of apparent approaches to boost device performance.     

Aqueous Photoelectrochemical CO2 Reduction to CO and Methanol over a Silicon Photocathode Functionalized with a Cobalt Phthalocyanine Molecular Catalyst

We report a precious-metal-free molecular catalyst-based photocathode that is active for aqueous CO₂ reduction to CO and methanol. The photoelectrode is composed of cobalt phthalocyanine molecules anchored on graphene oxide which is integrated via a (3-aminopropyl)triethoxysilane linker to p-type silicon protected by a thin film of titanium dioxide. The photocathode reduces CO₂ to CO with high selectivity at potentials as mild as 0 V versus the reversible hydrogen electrode (vs RHE). Methanol production is observed at an onset potential of −0.36 V vs RHE, and reaches a peak turnover frequency of 0.18 s⁻¹. To date, this is the only molecular catalyst-based photoelectrode that is active for the six-electron reduction of CO₂ to methanol. This work puts forth a strategy for interfacing molecular catalysts to p-type semiconductors and demonstrates state-of-the-art performance for photoelectrochemical CO₂ reduction to CO and methanol.     

Electrochemical monitoring of photoelectrocatalytic degradation of rhodamine B using TiO2 thin film modified graphite electrode

A commercially available TiO₂ powder (Degussa P25) has been used to prepare thin films on graphite plates. The photoelectrochemical degradation of rhodamine B was investigated using this photoelectrode. The effects of applied potential, pH, and initial rhodamine B concentration on the photoelectrocatalytic (PEC) degradation of rhodamine B using ultraviolet illuminated TiO₂/graphite (TiO₂/C) thin film electrode were examined and discussed. Also, direct photolysis, electrochemical oxidation, photocatalytic, and PEC degradation of rhodamine B were compared. Results show that the best responses for PEC are obtained at applied potential of 1.2?V vs. reference electrode, pH?4.0, and initial rhodamine B concentration of 4.2?mg?L^?1.     

Efficient solar-to-chemical conversion with chlorine photoanode

The photoelectrochemical water splitting is an artificial photosynthetic approach that could provide a sustainable supply of clean energy, however, the sluggish kinetics of the oxygen evolution reaction (OER) has been a bottleneck to the solar-to-chemical conversion. Here we report an implementation of 8% efficient photoanode based on the photoelectrolysis of saturated NaCl solution. Replacing the OER with the chlorine evolution reaction (CER) has transformed both the thermodynamic basis and the kinetic process of the photoelectrolysis, more chemical energy can be produced with much less driving force. The RuO₂/TiO₂/n-Si photoanode exhibits a high rate of photoelectrochemical conversion (35 mA/cm² at equilibrium potential), which steadily and exclusively produces Cl₂ without detectable O₂.     

Synthesis and properties of 3,4-dioxythiophene and 1,4-dialkoxybenzene based copolymers via direct C?H arylation: Dopant-free hole transport material for perovskite solar cells

Direct C H arylation coupling reaction has gained significant importance in synthesis of conjugated polymers for organic electronic applications. We report here a facile and straightforward method called “direct C H arylation” reaction to synthesize conjugated 3,4-dioxythiophene and 1,4-dialkoxybenzene based copolymers as hole transport material (HTM) for perovskite solar cells. Two electron-rich conjugated polymers P1-2 were synthesized, in which 1,4-dibromo-2,5-bis(dodecyloxy)benzene and 3,4-dialkoxy-thiophene units were used for polymerization. The resulting polymers were characterized and exhibited high solubility in organic solvents. Electrochemical and optical characterizations were carried out by cyclic voltammetry and UV–Vis–NIR absorption spectroscopy and found that these polymers show higher-lying HOMO energy levels with wide band gap. Density functional theory calculation was performed on these polymers ( P1-2 ) and correlated with our experimental results. Finally, perovskite solar cells were fabricated by solution-processable deposition of P1-2 as dopant-free HTM with device geometry ITO/SnO₂/Perovskite/HTM( P1 / P2 )/Ag and achieved a maximum power conversion efficiency of 5.28%. This study provides information on designing and simple preparation by direct C H arylation reaction of higher-lying HOMO energy level polymer as HTM for perovskite solar cells.     

An Integrated Photoelectrochemical–Chemical Loop for Solar‐Driven Overall Splitting of Hydrogen Sulfide

Abundant and toxic hydrogen sulfide (H₂S) from industry and nature has been traditionally considered a liability. However, it represents a potential resource if valuable H₂ and elemental sulfur can be simultaneously extracted through a H₂S splitting reaction. Herein a photochemical‐chemical loop linked by redox couples such as Fe²⁺/Fe³⁺ and I^?/I₃^? for photoelectrochemical H₂ production and H₂S chemical absorption redox reactions are reported. Using functionalized Si as photoelectrodes, H₂S was successfully split into elemental sulfur and H₂ with high stability and selectivity under simulated solar light. This new conceptual design will not only provide a possible route for using solar energy to convert H₂S into valuable resources, but also sheds light on some challenging photochemical reactions such as CH₄ activation and CO₂ reduction.     

Organic Photocathode Supported by Copper Nanosheets Array for Overall Water Splitting

The Z-scheme overall solar water splitting is a mimic of natural photosynthesis to convert solar energy into chemical energy. Since the energy levels of most organic semiconductors match well with the hydrogen evolution potential, they have great application prospects as photocathodes in Z-scheme photoelectrochemical systems. However, due to the weak light absorption and difficult carrier separation, the photocurrent density and onset potential of organic photocathodes are still low. To solve these problems, we introduced a copper nanosheets array (Cu NSA) framework under organic layers to increase the surface reaction sites, improve the light absorption and enhance the distribution range of built-in electric field simultaneously. As a result, the photocurrent density and onset potential of poly(3-hexylthiophene) : [6,6]-phenyl-C₆₁-butyric acid (P3HT : PCBM) photocathode were enhanced significantly. The onset potential increased by 50 mV to 0.65 V vs. RHE, and the photocurrent density reached −1 mA cm⁻² at 0 V vs. RHE, which was 18 times that of the sample without Cu NSA. The optimized photocathode was connected with titanium dioxide nanorods array photoanode in a tandem manner to realize the spontaneous overall water splitting. Without bias and co-catalyst, the photocurrent density was maintained at 110 μA cm⁻² and the solar-to-fuel conversion efficiency was 0.14 % in neutral solution. These results provide a feasible method for optimizing the performance of organic photocathodes.     

Photoelectrochemical Complexes of Fucoxanthin‐Chlorophyll Protein for Bio‐Photovoltaic Conversion with a High Open‐Circuit Photovoltage

Open‐circuit photovoltage (V_oc ) is among the critical parameters for achieving an efficient light‐to‐charge conversion in existing solar photovoltaic devices. Natural photosynthesis exploits light‐harvesting chlorophyll (Chl) protein complexes to transfer sunlight energy efficiently. We describe the exploitation of photosynthetic fucoxanthin‐chlorophyll protein (FCP) complexes for realizing photoelectrochemical cells with a high V_oc . An antenna‐dependent photocurrent response and a V_oc up to 0.72 V are observed and demonstrated in the bio‐photovoltaic devices fabricated with photosynthetic FCP complexes and TiO₂ nanostructures. Such high V_oc is determined by fucoxanthin in FCP complexes, and is rarely found in photoelectrochemical cells with other natural light‐harvesting antenna. We think that the FCP‐based bio‐photovoltaic conversion will provide an opportunity to fabricate environmental benign photoelectrochemical cells with high V_oc , and also help improve the understanding of the essential physics behind the light‐to‐charge conversion in photosynthetic complexes.     

A Multifunctional Polymer as an Interfacial Layer for Efficient and Stable Perovskite Solar Cells

Metal-cation defects and halogen-anion defects in perovskite films are critical to the efficiency and stability of perovskite solar cells (PSCs). In this work, a random polymer, poly(methyl methacrylate-co-acrylamide) (PMMA-AM), was synthesized to serve as an interfacial passivation layer for synergistically passivating the under-coordinated Pb²⁺ and anchor the I^- of the [PbI₆]⁴⁻ octahedron. Additionally, the interfacial PMMA-AM passivation layer cannot be destroyed during the hole transport layer deposition because of its low solubility in chlorobenzene. This passivation leads to an enhancement in the open-circuit voltage from 1.12 to 1.22 V and improved stability in solar cell devices, with the device maintaining 95 % of the initial power conversion efficiency (PCE) over 1000 h of maximum power point tracking. Additionally, a large-area solar cell module was fabricated using this approach, achieving a PCE of 20.64 %.