Synthesis of Large Surface‐Area g‐C3N4 Comodified with MnOx and Au‐TiO2 as Efficient Visible‐Light Photocatalysts for Fuel Production

Herein, this study successfully fabricates porous g‐C₃N₄‐based nanocomposites by decorating sheet‐like nanostructured MnO_x and subsequently coupling Au‐modified nanocrystalline TiO₂. It is clearly demonstrated that the as‐prepared amount‐optimized nanocomposite exhibits exceptional visible‐light photocatalytic activities for CO₂ conversion to CH₄ and for H₂ evolution, respectively by ≈28‐time (140 µmol g^?1 h^?1) and ≈31‐time (313 µmol g^?1 h^?1) enhancement compared to the widely accepted outstanding g‐C₃N₄ prepared with urea as the raw material, along with the calculated quantum efficiencies of ≈4.92% and 2.78% at 420 nm wavelength. It is confirmed mainly based on the steady‐state surface photovoltage spectra, transient‐state surface photovoltage responses, fluorescence spectra related to the produced ?OH amount, and electrochemical reduction curves that the exceptional photoactivities are comprehensively attributed to the large surface area (85.5 m² g^?1) due to the porous structure, to the greatly enhanced charge separation and to the introduced catalytic functions to the carrier‐related redox reactions by decorating MnO_x and coupling Au‐TiO₂, respectively, to modulate holes and electrons. Moreover, it is suggested mainly based on the photocatalytic experiments of CO₂ reduction with isotope ¹³CO₂ and D₂O that the produced ?CO₂ and ?H as active radicals would be dominant to initiate the conversion of CO₂ to CH₄.     

Leaf‐Mosaic‐Inspired Vine‐Like Graphitic Carbon Nitride Showing High Light Absorption and Efficient Photocatalytic Hydrogen Evolution

Green plants use solar energy efficiently in nature. Simulating the exquisite structure of a natural photosynthesis system may open a new approach for the construction of desirable photocatalysts with high light harvesting efficiency and performance. Herein, inspired by the excellent light utilization of “leaf mosaic” in plants, a novel vine‐like g‐C₃N₄ (V‐CN) is synthesized for the first time by copolymerizing urea with dicyandiamide‐formaldehyde (DF) resin. The as‐prepared V‐CN exhibits ultrahigh photocatalytic hydrogen production of 13.6 mmol g^?1 h^?1 under visible light and an apparent quantum yield of 12.7% at 420 nm, which is ≈38 times higher than that of traditional g‐C₃N₄, representing one of the highest‐activity g‐C₃N₄‐based photocatalysts. This super photocatalytic performance is derived from the unique leaf mosaic structure of V‐CN, which effectively improves its light utilization and affords a larger specific surface area. In addition, the introduction of DF resin further optimizes the energy band of V‐CN, extends its light absorption, and improves its crystallinity and interfacial charge transport, resulting in high performance. It is an easy and green strategy for the preparation of broad‐spectrum, high‐performance g‐C₃N₄, which presents significant advancement for the design of other nanophotocatalysts by simulating the fine structure of natural photosynthesis.     

Microwave‐Induced Metal Dissolution Synthesis of Core–Shell Copper Nanowires/ZnS for Visible Light Photocatalytic H2 Evolution

A microwave‐induced metal dissolution strategy is developed for in situ synthesis of copper nanowires/ZnS (CuNWs/ZnS) hybrids with core–shell structure. The CuNWs are used as microwave antennas to create local “super‐hot” surfaces to further initiate ZnS crystallization with full coverage on CuNWs. With the help of S^2?, the hot metal surface further results in the CuNWs dissolution with promoted Cu⁺ diffusion and incorporation into the ZnS lattice. With the narrowed bandgap of ZnS and the strongly coupled interface between CuNWs and ZnS created by microwaves, the as‐prepared hybrid composites exhibit an enhanced activity and stability in visible light for the photocatalytic H₂ evolution. The corresponding H₂ evolution rate reaches up to 10722 µmol h^?1 g^?1 with apparent quantum efficiency (AQE) of 69% under 420 nm LED irradiation, showing a remarkably high AQE among the noble‐metal free visible light‐driven photocatalysts and demonstrating a promising potential in practical applications to deal with the energy crisis.     

High Efficiency Photocatalytic Water Splitting Using 2D α‐Fe2O3/g‐C3N4 Z‐Scheme Catalysts

Photocatalysis is the most promising method for achieving artificial photosynthesis, but a bottleneck is encountered in finding materials that could efficiently promote the water splitting reaction. The nontoxicity, low cost, and versatility of photocatalysts make them especially attractive for this application. This study demonstrates that small amounts of α‐Fe₂O₃ nanosheets can actively promote exfoliation of g‐C₃N₄, producing 2D hybrid that exhibits tight interfaces and an all‐solid‐state Z‐scheme junction. These nanostructured hybrids present a high H₂ evolution rate >3 × 10⁴ µmol g^‐1 h^‐1 and external quantum efficiency of 44.35% at λ = 420 nm, the highest value so far reported among the family of g‐C₃N₄ photocatalysts. Besides effectively suppressing the recombination of electron–hole pairs, this Z‐scheme junction also exhibits activity toward overall water splitting without any sacrificial donor. The proposed synthetic route for controlled production of 2D g‐C₃N₄‐based structures provides a scalable alternative toward the development of highly efficient and active photocatalysts.     

Boosting Oxygen Evolution Kinetics by Mn–N–C Motifs with Tunable Spin State for Highly Efficient Solar‐Driven Water Splitting

Solar‐driven water splitting is in urgent need for sustainable energy research, for which accelerating oxygen evolution kinetics along with charge migration is the key issue. Herein, Mn³⁺ within π‐conjugated carbon nitride (C₃N₄) in form of Mn–N–C motifs is coordinated. The spin state (e_g orbital filling) of Mn centers is regulated by controlling the bond strength of Mn–N. It is demonstrated that Mn serves as intrinsic oxygen evolution reaction (OER) site and the kinetics is dependent on its spin state with an optimized e_g occupancy of ≈0.95. Specifically, the governing role of e_g occupancy originates from the varied binding strength between Mn and OER intermediates. Benefiting from the rapid spin state‐mediated OER kinetics, as well as extended optical absorption (to 600 nm) and accelerated charge separation by intercalated metal‐to‐ligand state, Mn–C₃N₄ stoichiometrically splits pure water with H₂ production rate up to 695.1 µmol g^?1 h^?1 under simulated sunlight irradiation (AM1.5), and achieves an apparent quantum efficiency of 4.0% at 420 nm, superior to most solid‐state based photocatalysts to date. This work for the first time correlates photocatalytic redox kinetics with the spin state of active sites, and suggests a nexus between photocatalysis and spin theory.     

Efficient Photocatalytic Nitrogen Fixation over Cuδ+‐Modified Defective ZnAl‐Layered Double Hydroxide Nanosheets

The photocatalytic reduction of nitrogen (N₂) with water (H₂O) as the reducing agent holds great promise as a sustainable future technology for the synthesis of ammonia (NH₃). Herein, the effect of oxygen vacancies and electron‐rich Cu^δ+ on the performance of zinc‐aluminium layered double hydroxide (ZnAl‐LDH) nanosheet photocatalysts for N₂ reduction to NH₃ under UV–vis excitation is systematically explored. Results show that a 0.5%‐ZnAl‐LDH nanosheet photocatalyst (containing 0.5 mol% Cu by metal basis) affords a remarkable NH₃ production rate of 110 µmol g^?1 h^?1 and excellent stability in pure water. The X‐ray absorption spectroscopy, electron paramagnetic resonance, and density functional theory calculations reveal that Cu addition imparts oxygen vacancies and coordinatively unsaturated Cu^δ+ (δ < 2) with electron‐rich property in the ZnAl‐LDH nanosheets, both of which readily contribute to efficient separation and transfer of photogenerated electrons and holes and promote N₂ adsorption, thereby both activating N₂ and facilitating its multielectrons reduction to NH₃.     

Optimization of Carbon‐ and Binder‐Free Au Nanoparticle‐Coated Ni Nanowire Electrodes for Lithium‐Oxygen Batteries

A Au nanoparticle‐coated Ni nanowire substrate without binder or carbon is used as the electrode (denoted as the Au/Ni electrode) for Li‐oxygen (Li‐O₂) batteries. A minimal amount of Au nanoparticles with sizes of <30 nm on a Ni nanowire substrate are coated using a simple electrodeposition method to the extent that maximum capacity can be utilized. This optimized, one body, Au/Ni electrode shows high capacities of 921 mAh g^?1_Au, 591 mAh g^?1_Au, and 359 mAh g^?1_Au, which are obtained at currents of 300 mAg^?1_Au, 500 mAg^?1_Au, and 1000 mAg^?1_Au respectively. More importantly, the Au/Ni electrode exhibits excellent cycle stability over 200 cycles.     

Tailoring Selectivity of Electrochemical Hydrogen Peroxide Generation by Tunable Pyrrolic‐Nitrogen‐Carbon

The electrochemical reduction of O₂ via a two‐electron reaction pathway to H₂O₂ provides a possibility for replacing the current anthraquinone process, enabling sustainable and decentralized H₂O₂ production. Here, a nitrogen‐rich few‐layered graphene (N‐FLG) with a tunable nitrogen configuration is developed for electrochemical H₂O₂ generation. A positive correlation between the content of pyrrolic‐N and the H₂O₂ selectivity is experimentally observed. The critical role of pyrrolic‐N is elucidated by the variable intermediate adsorption profiles as well as the dependent negative shifts of the pyrrolic‐N peak on X‐ray adsorption near edge structure spectra. By virtue of the optimized N doping configuration and the unique porous structure, the as‐fabricated N‐FLG electrocatalyst exhibits high selectivity toward electrochemical H₂O₂ synthesis as well as superior long‐term stability. To achieve high‐value products on both the anode and cathode with optimized energy efficiency, a practical device coupling electrochemical H₂O₂ generation and furfural oxidation is assembled, simultaneously enabling a high yield rate of H₂O₂ at the cathode (9.66 mol h^?1 g_cat^?1) and 2‐furoic acid at the anode (2.076 mol m^?2 h^?1) under a small cell voltage of 1.8 V.     

Drastic Layer‐Number‐Dependent Activity Enhancement in Photocatalytic H2 Evolution over nMoS2/CdS (n ≥ 1) Under Visible Light

Exploiting noble‐metal‐free cocatalysts is of huge interest for photocatalytic water splitting using solar energy. As an efficient cocatalyst in photocatalysis, MoS₂ is shown promise as a low‐cost alternative to Pt for hydrogen evolution. Here we report a systematical study on controlled synthesis of MoS₂ with layer number ranging from ≈1 to 112 and their activities for photocatalytic H₂ evolution over commercial CdS. A drastic increase in photocatalytic H₂ evolution is observed with decreasing MoS₂ layer number. Particularly for the single‐layer (SL) MoS₂, the SL‐MoS₂/CdS sample reaches a high H₂ generation rate of ≈2.01 × 10^?3m h^?1 in Na₂S–Na₂SO₃ solutions and ≈2.59 × 10^?3m h^?1 in lactic acid solutions, corresponding to an apparent quantum efficiency of 30.2% and 38.4% at 420 nm, respectively. In addition to the more exposed edges and unsaturated active S atoms, valence band–XPS and Mott–Schottky plots analysis indicate that the SL MoS₂ has the more negative conduction band energy level than the H⁺/H₂ potential, facilitating the hydrogen reduction.     

Efficient Plasmonic Au/CdSe Nanodumbbell for Photoelectrochemical Hydrogen Generation beyond Visible Region

In this communication, light harvesting and photoelectrochemical (PEC) hydrogen generation beyond the visible region are realized by an anisotropic plasmonic metal/semiconductor hybrid photocatalyst with precise control of their topology and heterointerface. Controlling the intended configuration of the photocatalytic semiconductor to anisotropic Au nanorods' plasmonic hot spots, through a water phase cation exchange strategy, the site‐selective overgrowth of a CdSe shell evolving from a core/shell to a nanodumbbell is realized successfully. Using this strategy, tip‐preferred efficient photoinduced electron/hole separation and plasmon enhancement can be realized. Thus, the PEC hydrogen generation activity of the Au/CdSe nanodumbbell is 45.29 µmol cm^?2 h^?1 (nearly 4 times than the core/shell structure) beyond vis (λ > 700 nm) illumination and exhibits a high faradic efficiency of 96% and excellent stability with a constant photocurrent for 5 days. Using surface photovoltage microscopy, it is further demonstrated that the efficient plasmonic hot charge spatial separation, which hot electrons can inject into CdSe semiconductors, leads to excellent performance in the Au/CdSe nanodumbbell.     

Au/TiO2–gC3N4 Nanocomposites for Enhanced Photocatalytic H2 Production from Water under Visible Light Irradiation with Very Low Quantities of Sacrificial Agents

Here for the first time the design and optimization are presented of a three‐component Au/TiO₂–gC₃N₄ nanocomposite photocatalyst able to efficiently produce H₂ from water using very low amounts of sacrificial agents and under visible light irradiation. This enhanced photocatalytic behavior compared to Au/TiO₂ and Au/gC₃N₄ materials is the result of synergetic effects due to high quality assembly and interface between the three components. This optimized nanoscale assembly characterized by simultaneous favorable nanoheterojunction formation between g‐C₃N₄ and TiO₂ semiconductors, as well as AuNPs/gC₃N₄ and AuNPs/TiO₂ junctions, leads to enhanced visible light harvesting, charge separation, and H₂ production. This composite photocatalyst yields a high H₂ production (350 µmol^?1 h^?1 g_catalyst^?1) under visible light irradiation with minimal amounts of sacrificial agent (≤1 vol%), corresponding to activities much higher than reported so far under comparable conditions.     

2D Metal Organic Framework Nanosheet: A Universal Platform Promoting Highly Efficient Visible‐Light‐Induced Hydrogen Production

2D metal organic frameworks (MOF) have received tremendous attention due to their organic–inorganic hybrid nature, large surface area, highly exposed active sites, and ultrathin thickness. However, the application of 2D MOF in light‐to‐hydrogen (H₂) conversion is rarely reported. Here, a novel 2D MOF [Ni(phen)(oba)]_n·0.5nH₂O (phen = 1,10‐phenanthroline, oba = 4,4′‐oxybis(benzoate)) is for the first time employed as a general, high‐performance, and earth‐abundant platform to support CdS or Zn_0.8Cd_0.2S for achieving tremendously improved visible‐light‐induced H₂‐production activity. Particularly, the CdS‐loaded 2D MOF exhibits an excellent H₂‐production activity of 45 201 µmol h^?1 g^?1, even exceeding that of Pt‐loaded CdS by 185%. Advanced characterizations, e.g., synchrotron‐based X‐ray absorption near edge structure, and theoretical calculations disclose that the interactive nature between 2D MOF and CdS, combined with the high surface area, abundant reactive centers, and favorable band structure of 2D MOFs, synergistically contribute to this distinguished photocatalytic performance. The work not only demonstrates that the earth‐abundant 2D MOF can serve as a versatile and effective platform supporting metal sulfides to boost their photocatalytic H₂‐production performance without noble‐metal co‐catalysts, but also paves avenues to the design and synthesis of 2D‐MOF‐based heterostructures for catalysis and electronics applications.     

Heat Diffusion‐Induced Gradient Energy Level in Multishell Bisulfides for Highly Efficient Photocatalytic Hydrogen Production

Insufficient light absorption and low carrier separation/transfer efficiency constitute two key issues that hinder the development of efficient photocatalytic hydrogen production. Here, multishell ZnS/CoS₂ bisulfide microspheres with gradient distribution of Zn based on the heat diffusion theory are designed. The Zn distribution can be adjusted by regulating the heating rate and manipulating the diffusion coefficients of the different elements conforming the multishell photocatalyst. Because of the unique structure, a gradient energy level is created from the core to the exterior of the multishell microspheres, which effectively facilitates the exciton separation and electron transfer. In addition, stronger light absorption and larger specific surface area have been achieved in the multishell ZnS/CoS₂ photocatalysts. As a result, the multishell ZnS/CoS₂ microspheres with gradient distribution of Zn exhibit a remarkable hydrogen production rate of 8001 µ mol g^?1 h^?1, which is 3.5 times higher than that of the normal multishell ZnS/CoS₂ particles with well‐distributed Zn and 11.3 times higher than that of the mixed nonshell ZnS and CoS₂ particles. This work demonstrates for the first time that controlling the diffusion rate of the different elements in the semiconductor is an effective route to simultaneously regulate morphology and structure to design highly efficient photocatalysts.     

A Heterogeneous Carbon Nitride–Nickel Photocatalyst for Efficient Low‐Temperature CO2 Methanation

The Sabatier reaction, i.e., the hydrogenation of CO₂ to methane (CH₄) using hydrogen (H₂), constitutes a potentially scalable method to store energy in a product with a high energy density. However, up to today, this reaction has been mainly thermally driven and conducted at high temperatures (typically 400–600 °C). Using light as a renewable energy source will allow for a more sustainable process by lowering the reaction temperature. Here, it is demonstrated that Ni nanoparticles support on graphitic carbon nitride (g‐CN) are a highly efficient and stable photocatalyst for the gas‐phase CO₂ methanation at low temperature (150 °C). Detailed mechanistic studies reveal a very low activation energy for the reaction and high activity under visible light, leading to a remarkable and continuous CH₄ production of 28 µmol g^?1 h^?1 of CH₄ for 24 h.     

Carbon Nitride/Reduced Graphene Oxide Film with Enhanced Electron Diffusion Length: An Efficient Photo‐Electrochemical Cell for Hydrogen Generation

Polymeric carbon nitride (CN) has emerged as a promising semiconductor for energy‐related applications. However, its utilization in photo‐electrochemical cells is still very limited owing to poor electron–hole separation efficiency, short electron diffusion length, and low absorption coefficient. Here the synthesis of a highly porous carbon nitride/reduced graphene oxide (CN‐rGO) film with good photo‐electrochemical properties is reported. The CN‐rGO film exhibits long electron diffusion length and high electrochemical active surface area, good charge separation, and enhanced light‐harvesting properties. The film displays a 20‐fold enhancement of photocurrent density over pristine CN, reaching up to 75 µA cm^?2 at 1.23 V versus reversible hydrogen electrode (RHE) in an alkaline solution, as well as stability over a wide pH range. Photocurrent measurements with a hole scavenger reveal a photocurrent density of 660 µA cm^?2 at 1.23 V versus RHE and a quantum efficiency of 60% at 400 nm, resulting in the production of 0.8 mol h^?1 g^?1 of hydrogen. The substantial photo‐electrochemical activity enhancement and hydrogen production together with the low price, high electrochemical surface area, long electron diffusion length, stability under harsh condition, and tunable photophysical properties of CN materials open many possibilities for their utilization in (photo)electrochemical and electronic devices.     

Progress toward a biomimetic leaf: 4,000 h of hydrogen production by coating‐stabilized nongrowing photosynthetic Rhodopseudomonas palustris

Intact cells are the most stable form of nature's photosynthetic machinery. Coating‐immobilized microbes have the potential to revolutionize the design of photoabsorbers for conversion of sunlight into fuels. Multi‐layer adhesive polymer coatings could spatially combine photoreactive bacteria and algae (complementary biological irradiance spectra) creating high surface area, thin, flexible structures optimized for light trapping, and production of hydrogen (H₂) from water, lignin, pollutants, or waste organics. We report a model coating system which produced 2.08 ± 0.01 mmol H₂ m^?2 h^?1 for 4,000 h with nongrowing Rhodopseudomonas palustris, a purple nonsulfur photosynthetic bacterium. This adhesive, flexible, nanoporous Rps. palustris latex coating produced 8.24 ± 0.03 mol H₂ m^?2 in an argon atmosphere when supplied with acetate and light. A simple low‐pressure hydrogen production and trapping system was tested using a 100 cm² coating. Rps. palustris CGA009 was combined in a bilayer coating with a carotenoid‐less mutant of Rps. palustris (CrtI^?) deficient in peripheral light harvesting (LH2) function. Cryogenic field emission gun scanning electron microscopy (cryo‐FEG‐SEM) and high‐pressure freezing were used to visualize the microstructure of hydrated coatings. A light interaction and reactivity model was evaluated to predict optimal coating thickness for light absorption using the Kubelka‐Munk theory (KMT) of reflectance and absorptance. A two‐flux model predicted light saturation thickness with good agreement to observed H₂ evolution rate. A combined materials and modeling approach could be used for guiding cellular engineering of light trapping and reactivity to enhance overall photosynthetic efficiency per meter square of sunlight incident on photocatalysts. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010     

A blue chemiluminescence in the reaction of umbelliferone with hypochlorite

A strongly fluorescing 7-hydroxycoumarin (umbelliferone, U) oxidized in dilute (10 μmol/L-0, 1 mol/L) aqueous solution with CIO^? or CIO^? + H₂O₂ (but not with H₂O₂ alone) produces a strong chemiluminescence (CL). Light emission kinetics depends on the pH of solution (4.0–10.5) and the reaction has a low activation energy E_a = 31 ± 2 kJ/mol (285–310 K). The spectrum covers the fluorescence of umbelliferone (400–550 nm, λ_max 460nm). No red emission typical of ¹Δg, ¹Σ⁺g (O₂)₂ is observed either in the umbelliferone +CIO^? or the umbelliferone +CIO^? + H₂O₂ solution. The possible mechanism of CL and concomitant degradative oxidation of umbelliferone is discussed.     

Controllable Synthesis of Mesoporous TiO2 Polymorphs with Tunable Crystal Structure for Enhanced Photocatalytic H2 Production

Multiphasic titanium dioxide (TiO₂) possessing abundant heterophase junctions have been widely used for various photocatalytic applications. Current synthesis of multiphasic TiO₂ mainly involves the process of thermal treatment and multiple steps of rigorous reactions, which is adverse to controlling the crystal phases and phase ratios of multiphasic TiO₂. Meanwhile, the resulting products have relatively low surface area and nonporous structure. Here, a facile polymer‐assisted coordination‐mediated self‐assembly method to synthesize mesoporous TiO₂ polymorphs with controllable heterophase junctions and large surface area by using polyethylenimine as the porogen in an acidic aqueous synthesis system is reported. Using this approach, the crystal phases (triphase, biphase, and monophase) and phase compositions (0–100%) are easily tailored by selecting the suitable acidic media. Furthermore, the specific surface areas (77–228 m² g^?1) and pore sizes (2.9–10.1 nm) are readily tailored by changing the reaction temperature. The photocatalytic activity of mesoporous TiO₂ polymorphs is evaluated by photocatalytic hydrogen evolution. The triphasic TiO₂ exhibits an excellent photocatalytic H₂ generation rate of 3.57 mmol h^?1 g^?1 as compared to other polymorphs, which is attributed to the synergistic effects of heterophase junctions and mesostructure. The band diagram of possible electron transfer pathway for triphasic TiO₂ is also elucidated.     

Nitrogen‐Doped Carbon‐Coated CuO‐In2O3 p–n Heterojunction for Remarkable Photocatalytic Hydrogen Evolution

CuO as a catalyst has shown promising application prospects in photocatalytic splitting of water into hydrogen (H₂). However, the instability of CuO in amine aqueous solution limits the applications of CuO‐based photocatalysts in the photocatalytic H₂ evolution. In this work, a novel dodecahedral nitrogen (N)‐doped carbon (C) coated CuO‐In₂O₃ p–n heterojunction (DNCPH) is designed and synthesized by directly pyrolyzing benzimidazole‐modified dodecahedral Cu/In‐based metal‐organic frameworks, showing long‐term stability in triethanolamine (TEOA) aqueous solution and excellent photocatalytic H₂ production efficiency. The improved stability of DNCPH in TEOA solution is ascribed to the alleviation of electron deficiency in CuO by forming the p–n heterojunction and the protection with coated N‐doped C layer. Based on detailed theoretical calculations and experimental studies, it is found that the improved separation efficiency of photogenerated electron/hole pairs and the mediated adsorption behavior (|?G_H*|→0) by coupling N‐doped C layer with CuO‐In₂O₃ p–n heterojunction lead to the excellent photocatalytic H₂ production efficiency of DNCPH. This work provides a feasible strategy for effectively applying CuO‐based photocatalysts in photocatalytic H₂ production.     

Light‐Dependent and Aeration‐Independent Gram‐Scale Hydroxylation of Cyclohexane to Cyclohexanol by CYP450 Harboring Synechocystis sp. PCC 6803

Oxygenase‐containing cyanobacteria constitute promising whole‐cell biocatalysts for oxyfunctionalization reactions. Photosynthetic water oxidation thereby delivers the required cosubstrates, that is activated reduction equivalents and O₂, sustainably. A recombinant Synechocystis sp. PCC 6803 strain showing unprecedentedly high photosynthesis‐driven oxyfunctionalization activities is developed, and its technical applicability is evaluated. The cells functionally synthesize a heterologous cytochrome P450 monooxygenase enabling cyclohexane hydroxylation. The biocatalyst‐specific reaction rate is found to be light‐dependent, reaching 26.3 ± 0.6 U g_CDW^?1 (U = μmol min^?1 and cell dry weight [CDW]) at a light intensity of 150 µmol_photons m^?2 s^?1. In situ substrate supply via a two‐liquid phase system increases the initial specific activity to 39.2 ± 0.7 U g_CDW^?1 and stabilizes the biotransformation by preventing cell toxification. This results in a tenfold increased specific product yield of 4.5 g_cyclohexanol g_CDW^?1 as compared to the single aqueous phase system. Subsequently, the biotransformation is scaled from a shake flask to a 3 L stirred‐tank photobioreactor setup. In situ O₂ generation via photosynthetic water oxidation allows a nonaerated process operation, thus circumventing substrate evaporation as the most critical factor limiting the process performance and stability. This study for the first time exemplifies the technical applicability of cyanobacteria for aeration‐independent light‐driven oxyfunctionalization reactions involving highly toxic and volatile substrates.