Photocatalytic O2 Production Research Articles

Multifunctional Hydrogel Containing Oxygen Vacancy‐Rich WOx for Synergistic Photocatalytic O2 Production and Photothermal Therapy Promoting Bacteria‐Infected Diabetic Wound Healing

AbstractAn effective method capable of simultaneously providing antibacterial activity, blood glucose regulation, and angiogenesis promotion for healing bacteria‐infected diabetic wounds is not reported to date, but urgently required. In this study, a hydrogel composite (γ‐PGA/PDA/GOx/WOx (PPGW)), endowed with these desired attributes is fabricated by incorporating polydopamine (PDA), glucose oxidase (GOx), and tungsten oxide (WOx) nanowires into the poly(γ‐glutamic acid) (γ‐PGA) framework. The exceptional photothermal conversion properties of PDA facilitated notable antibacterial effects on bacteria‐infected diabetic wounds; GOx regulated high blood glucose by consuming glucose and generating hydrogen peroxide (H2O2); while WOx nanowires displayed remarkable photocatalytic abilities, converting H2O2 into oxygen (O2) when exposed to 808‐nm near‐infrared radiation. Density functional theory calculations and experiments are conducted to confirm the mechanism of WOx‐mediated photocatalytic degradation of H2O2 to produce O2. These transformations aided in alleviating the hypoxic conditions in wounds associated with diabetes, expediting angiogenesis, and fostering cell crawling and proliferation. Consequently, the multifunctional hydrogel dressing PPGW, featuring photothermal, antibacterial, and enzyme‐catalyzed activity reduces hyperglycemia at the wound site. Moreover, photocatalytic O2 production represents a promising strategy for addressing chronic bacteria‐infected diabetic wounds.

Photocatalytic Oxygen Evolution under Visible Light Mediated by Molecular Heterostructures.

Due to their structural and property tunability, semiconductive conjugated polymers (CPs) have emerged as promising candidates for photocatalytic water splitting. Compared with inorganic materials, the photocatalytic performance of mono-component polymers was limited by the fast recombination of photoexcited charge carriers, and they always needed to catch up to expectations. To this end, researchers established molecular donor-acceptor heterostructures, which could notably promote oxygen production efficiency due to their more effective charge carrier separation. In this work, easy Schiff base reactions between side-chain -CHO groups and terminal -NH2 groups were used to introduce benzene and perylene diimide (PDI) into the molecular heterostructure to serve as electron donors (D) and electron acceptors (A). In particular, for the first time, we employed the molecular heterostructures of CPs to promote photocatalytic O2 production. One prepared molecular heterostructure was demonstrated to improve oxygen generation rate (up to 0.53 mmol g-1 h-1) through visible light-driven water splitting. Interestingly, based on the photoelectric properties, a stepwise two-electron/two-electron pathway constituted the photocatalytic mechanism for oxygen production with the molecular heterostructure. These results provide insights into designing and fabricating high-performance molecular heterostructures for photocatalytic oxygen production.

Spin selection in atomic-level chiral metal oxide for photocatalysis

The spin degree of freedom is an important and intrinsic parameter in boosting carrier dynamics and surface reaction kinetics of photocatalysis. Here we show that chiral structure in ZnO can induce spin selectivity effect to promote photocatalytic performance. The ZnO crystals synthesized using chiral methionine molecules as symmetry-breaking agents show hierarchical chirality. Magnetic circular dichroism spectroscopic and magnetic conductive-probe atomic force microscopic measurements demonstrate that chiral structure acts as spin filters and induces spin polarization in photoinduced carriers. The polarized carriers not only possess the prolonged carrier lifetime, but also increase the triplet species instead of singlet byproducts during reaction. Accordingly, the left- and right-hand chiral ZnO exhibit 2.0- and 1.9-times higher activity in photocatalytic O2 production and 2.5- and 2.0-times higher activities in contaminant photodegradation, respectively, compared with achiral ZnO. This work provides a feasible strategy to manipulate the spin properties in metal oxides for electron spin-related redox catalysis.

Dual Cocatalysts Synergistically Promote Perylene Diimide Polymer Charge Transfer for Enhanced Photocatalytic Water Oxidation

Water oxidation is a critical reaction in artificial photosynthesis which is limited by a high reaction energy barrier and often requires matching cocatalysts. Dual cocatalysts Co3O4 and Pt are combined with a perylene diimide (PDI) polymer, accomplishing a photocatalytic O2 production rate of 24.4 mmol g–1 h–1 under visible light irradiation, which is a 5.4-fold enhancement compared with PDI alone. Moreover, the apparent quantum yield of the O2 evolution reaction reaches 6.9% at 420 nm and remains 1.2% at 590 nm. The dual cocatalysts-constructed interfacial electric fields provide an anisotropic driving force for photogenerated holes to Co3O4 and electrons to Pt, synergistically improving the spatial charge separation efficiency for water oxidation. Co3O4 molecules serve as active sites for the water oxidation reaction to improve the utilization of photogenerated holes on the surface. This work provides a valuable demonstration of the interaction process and mechanism of cocatalysts, guiding the selection of cocatalysts for high-efficiency solar energy conversion.

In Situ Formed Z-Scheme Graphdiyne Heterojunction Realizes NIR-Photocatalytic Oxygen Evolution and Selective Radiosensitization for Hypoxic Tumors.

Photon radiotherapy is a common tool in the armory against tumors, but it is limited by hypoxia-related radioresistance of tumors and radiotoxicity to normal tissues. Here, we constructed a spatiotemporally controlled synergistic therapy platform based on the heterostructured CuO@Graphdiyne (CuO@GDY) nanocatalyst for simultaneously addressing the two key problems above in radiotherapy. First, the in situ formed Z-scheme CuO@GDY heterojunction performs highly efficient and controlled photocatalytic O2 evolution upon near-infrared (NIR) laser stimulation for tumor hypoxia alleviation. Subsequently, the CuO@GDY nanocatalyst with X-ray-stimulated Cu+ active sites can accelerate Fenton-like catalysis of ·OH production by responding to endogenous H2O2 for the selective killing of tumor cells rather than normal cells. In this way, the sequential combination of NIR-triggered photocatalytic O2 production and X-ray-accelerated Fenton-like reaction can lead to a comprehensive radiosensitization. Overall, this synergism underscores a controllable and precise therapy modality for simultaneously unlocking the hypoxia and non-selectivity in radiotherapy.

Z-scheme MoS2/Co3S4@PEG nanoflowers: Intracellular NIR-II photocatalytic O2 production facilitating hypoxic tumor therapy

Intratumoral hypoxia, which is in favour of cancer cell proliferation, invasion and metastasis, also inhibits photodynamic therapy (PDT) badly. Herein, second near-infrared (NIR-II) photocatalytic O2 production is established to realize hypoxia relief. MoS2/Co3S4@PEG (MSCs@PEG) nanoflowers (100–150 nm) are prepared via a two-step hydrothermal method. These samples possess high NIR-II harvest and photothermal conversion (39.8 %, 1064 nm) ability. That not only reveals photothermal therapy (PTT) but also lifts the thermal energy of nanomaterials to replenish extra energy, making sure the co-excitation of MoS2 (1.14 eV) and Co3S4 (1.40 eV) by low-energy NIR-II (1064 nm, 1.16 eV) laser. The investigation of band structure further displays the Z-Scheme characterization of MSCs heterostructure. These photo-excited holes/electrons hold great redox ability to form O2 (water splitting) and reactive oxygen species (ROS), simultaneously. In addition, MSC-2@PEG can be served to mimic catalase, peroxidase, and glutathione (GSH) oxidase to further boost oxidative stress. It is noted that heterostructure discovers the greater nanozyme activity, attributing to the lower resistance for charge transfer. Moreover, MSC-2@PEG displays a novel biodegradation ability to induce the elimination via urine and faeces within 14 days. Given the superparamagnetic and photothermal effect, the nanocomposite can be used as magnetic resonance and photothermal imaging (MRI and PTI) contrast. Associated with dual-imaging, intracellular O2 supplementation, and synergistic chemotherapy (CDT)/PTT/PDT, MSC-2@PEG possess great tumor inhibition that also efficiently motivates immune response for anticancer.

Construction of g-C3N4 nanotube/Ag3PO4 S-scheme heterojunction for enhanced photocatalytic oxygen generation

Heterojunction engineering is considered as a hopeful approach to ameliorate the separation of photogenerated carriers of photocatalysts, realizing efficient water-splitting performance. In this study, an organic-inorganic S-scheme of a one-dimensional g-C3N4 nanotube (TCN)/Ag3PO4 photocatalytic system with high photocatalytic water oxidation activity was designed by coupling g-C3N4 nanotubes over Ag3PO4 particles through a chemical coprecipitation method. The TCN/Ag3PO4 heterojunction demonstrated excellent photocatalytic O2 production with an O2 evolution rate of up to 370.2 μmol·L−1·h−1. X-ray photoelectron spectroscopy analysis showed that electron migration between TCN and Ag3PO4 led to the formation of an internal electric field pointing from TCN to Ag3PO4, which drove the S-scheme charge transfer mode between TCN and Ag3PO4. Accordingly, the TCN/Ag3PO4 heterojunction possessed fast charge separation and high redox ability, leading to high photoactivity and photostability. This research provides a new strategy for fabricating highly efficient inorganic-organic S-scheme photocatalysts for O2 production.

Liberating photocarriers in mesoporous single-crystalline SrTaO2N for efficient solar water splitting

Porous single-crystalline SrTaO2N, combining structural homogeneity and high porosity, afford a great promise as an active photocatalyst. The lack of grain boundaries in SrTaO2N porous single crystals (PSCs) enables fast photocarrier migration from bulk to the surface whilst the high porosity offers adequate accessible surface to perform photocatalytic reactions. In this work, we demonstrate a facile synthesis of SrTaO2N PSCs via a topotactic conversion route. These SrTaO2N PSCs deliver exceptional activity and stability for photocatalytic O2 production from water with a record-breaking apparent quantum efficiency as high as 17.9% at 420 ± 20 nm. Overall water splitting with H2/O2 equals 2 has also been attained in a Z-scheme system employing SrTaO2N PSCs as the O2-evolution moiety. These results signify a paradigm to improve photocatalytic performance based on PSCs, which extends the toolbox to achieve efficient solar water splitting over conventional photocatalysts.

Interfacial optimization of Z-scheme Ag3PO4/MoS2 nanoflower sphere heterojunction toward synergistic enhancement of visible-light-driven photocatalytic oxygen evolution and degradation of organic pollutant

Samples of flower-like MoS2 nanosphere-modified Ag3PO4 (Ag3PO4/MoS2) were prepared by a facile and reliable method. The morphology and crystal structure of the Ag3PO4/MoS2 composites were investigated by high-resolution transmission electron microscopy, X-ray diffraction, specific surface areas, and X-ray photoelectron spectroscopy. Analysis results indicated that Ag3PO4 particles were distributed conformably on the surface of flower-like MoS2 spheres, and both formed an enhanced heterojunction structure. Fluorescence spectra, surface photocurrent spectra, and electrochemical impedance spectroscopic results showed that an appropriate amount of MoS2 modification (6 mg) could effectively improve the generation, separation, and migration efficiency of the photogenerated electron/hole pairs (e−/h+). The photocatalytic activity of the samples was evaluated by photocatalytic O2 production and photodegradation of the organic molecules under visible-light irradiation. With the increase in the amount of MoS2, the photocatalytic activity of the Ag3PO4/MoS2 samples increased first and then decreased. The photocatalytic rate reached the fastest when the mass of MoS2 was 6 mg, which was 7.66- and 9.28-fold of that of pure Ag3PO4 for photocatalytic O2 production and photodegradation of organic molecules, respectively. Sacrificial reagent experiments and electron spin resonance spectra showed that superoxide radicals (•O2−) and holes (h+) played a major role in the photocatalytic reaction process. The enhanced photocatalytic performance could be ascribed to the interfacial optimization and formation of Z-scheme heterojunction.

Mimicking Thylakoid Membrane with Chlorophyll/TiO2/Lipid Co-Assembly for Light-Harvesting and Oxygen Releasing.

There is a growing interest in the design and construction of artificial photosythetic materials for solar energy utilization and conversion. Inspired by the structure of thylakoid membrane, we present here a hybrid construct for light-harvesting and oxygen releasing. Our design conjugates chlorophyll to TiO2 in a native-like membrane environment. The natural bilayer structure of lipids is utilized to localize the amphiphilic chlorophyll a and hydrophobic tetrabutyl titanate TBOT in the liposomal membrane during hydration process. The coassembled structure, which mimics the essential organization of the thylakoid membrane, is characterized using a combination of field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectrometer (EDS), Ramam spectra, pressure (π)-area (Α) isotherms, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) analysis. Our results demonstrate successful insertation of chlorophyll a in the membrane and confirm the in situ formation of TiO2 nanoshell confined at the lipid bilayer/water interface. We further show that the hybrid liposomes exhibit unambiguous photoactivity in visible light-harvesting and oxygen release, likely resulting from a larger specific surface area of the TiO2 shell, an efficient interfacial conjugation of the chlorophyll molecules with the thin TiO2 layer. The density functional theory (DFT) calculations were in accordance with the eletron injection processes.We expect that the present work will open a new insight into interfacial recombination between light-harvesting pigments and their sensitized photocatalysis, and develop a new kind of artificial photosynthetic materials with zero-cost of environmental degradation and high efficiency for the photocatalytic O2 production.

Lattice Defects Engineering in W-, Zr-doped BiVO4 by Flame Spray Pyrolysis: Enhancing Photocatalytic O2 Evolution.

A flame spray pyrolysis (FSP) method has been developed, for controlled doping of BiVO4 nanoparticles with W and Zr in tandem with the oxygen vacancies (Vo) of the BiVO4 lattice. Based on XPS and Raman data, we show that the nanolattice of W-BiVO4 and Zr-BiO4 can be controlled to achieve optimal O2 evolution from H2O photocatalysis. A synergistic effect is found between the W- and Zr-doping level in correlation with the Vo-concentration. FSP- made W-BiVO4 show optimal photocatalytic O2-production from H2O, up to 1020 μmol/(g × h) for 5%W-BiVO4, while the best performing Zr-doped achieved 970 μmol/(g × h) for 5%Zr-BiVO4. Higher W-or Zr-doping resulted in deterioration in photocatalytic O2-production from H2O. Thus, engineering of FSP-made BiVO4 nanoparticles by precise control of the lattice and doping-level, allows significant enhancement of the photocatalytic O2-evolution efficiency. Technology-wise, the present work demonstrates that flame spray pyrolysis as an inherently scalable technology, allows precise control of the BiVO4 nanolattice, to achieve significant improvement of its photocatalytic efficiency.

MOF-derived bimetallic Fe-Ni-P nanotubes with tunable compositions for dye-sensitized photocatalytic H2 and O2 production

Dye-sensitized systems show promising in photocatalysis because they can separate the tasks of light absorption, charge generation and surface catalysis to two coupled components. In this system, it is crucial to develop suitable catalysts capable of receiving dye-injected charges and having high activity to a given reaction. Aiming to photocatalytic H2 and O2 production, we present a metal-organic framework derived route to prepare bimetallic Fe-Ni-P nanotubes using Fe-Ni-MIL-88 nanorods as templates. When integrated with different dyes, these Fe-Ni-P nanotubes can serve as efficient catalysts for photocatalytic H2 and O2 production, respectively. Additionally, catalytic activities of such dye-sensitized systems can be conveniently regulated by tailoring the metal compositions in Fe-Ni-P nanotubes. The photocatalytic H2 production of Fe1-Ni2-P can reach 5420 μmol gcat−1 h−1 under eosin-Y sensitization, which is 24 times and 6.7 times higher than Fe2P and Ni2P, respectively. The photocatalytic O2 production of Fe1-Ni2-P can reach 900.3 μmol gcat−1 h−1 under [Ru(bpy)3]Cl2 sensitization, about 4.6 times and 2.9 times higher than Fe2P and Ni2P. The roles of different components in the system have been explored and corresponding working mechanism is proposed. This work demonstrates a new type of dye-sensitized systems consisting of bimetallic phosphides and provides a facile route to regulate their photocatalytic performance.

A Novel Ag(I)-Containing Polyoxometalate-Based MOF for Visible-Light-Driven Water Oxidation

A novel 3D Ag(I)-containing polyoxometalate-based MOF of H17[Ag9(AgH8W11O44)2(BPY)9]·2.5H2O (WAg–BPY; BPY = 4,4′-bipyridine) has been solvothermally synthesized, and structurally characterized by elemental analyses, IR spectrum, UV–Vis spectrum, powder X-ray diffraction (PXRD) and single-crystal X-ray diffraction. WAg–BPY exhibits highly efficient photocatalytic O2 production (964 μmol g−1 in the first 10 min) under visible-light irradiation. More interestingly, transient photocurrent experiments confirm the charge separation and transfer process for the possible mechanism in the photocatalytic reaction. The high photocatalytic efficiency, high stability and good recyclability of the catalyst WAg–BPY demonstrates that Ag(I)-containing polyoxometalate units are crucial factor for water oxidation over heterogeneous systems. The successful synthesis of WAg–BPY not only enriches polyoxometalate-based hybrid materials, but also represents the advantages of the Ag(I)-containing complexes for the potential applications such as heterogeneous photocatalysis and so on.

An Organic Molecular Photocatalyst Releasing Oxygen from Water.

Artificial photosynthesis employing solar energy is one of the best means of reaching a sustainable energy cycle, in which water is oxidized to oxygen and supplies electrons for fuel generation. The development of suitable oxygen evolution materials driven by sunlight is hence the most challenging research topic in the field of photocatalysis. Herein, photocatalytic O2 production from water at a rate of 22.6 μmol h-1 was performed by using a pyrene-based organic molecule constructed through the Ullmann coupling reaction. Its significantly improved light-harvesting ability and notably accelerated separation and transfer of photogenerated charges enhanced the O2 evolution efficiency. This study highlights the structural design of organic molecules applied to photocatalytic water splitting.

Metal-free broad-spectrum PTCDA/g-C3N4 Z-scheme photocatalysts for enhanced photocatalytic water oxidation

Exploiting highly-efficient, broad-spectrum responsive and noble-metal-free water oxidation photocatalyst is a major challenge in the field of photocatalysis. Herein, we tackle this challenge by synthesizing Z-scheme PTCDA/g-C3N4 photocatalysts, which can absorb light with wavelength short than 600 nm, for visible light photocatalytic O2 production from water. Owing to the evident conduction and valance band energy level difference between PTCDA and g-C3N4, the PTCDA/g-C3N4 photocatalysts exhibit efficient charge carrier separation through a Z-scheme mechanism, as demonstrated by the transient photocurrent responses and time-resolved fluorescence decay spectra analysis. Benefitting from the synergetic effect of the broad visible light absorption capacity and efficient charge separation, the optimized PTCDA/g-C3N4 photocatalyst shows the highest O2 evolution rate of 847 μmol·h−1·g−1 under visible light irradiation in the presence of Co3O4 as a cocatalyst and AgNO3 as the sacrificial reagent. An apparent quantum yield of 4.5% was achieved under monochromatic light irradiation at 420 nm.

Cobalt-based cubane molecular co-catalysts for photocatalytic water oxidation by polymeric carbon nitrides

In artificial photocatalysis, sluggish kinetics of hole transfer and the high recombination rate of charge have been the Achilles’ heel of photocatalytic conversion efficiency. The development of co-catalysts for promoting exciton splitting and charge separation has therefore gained continuous attention. Herein, “Co4O4” cubane complex Co4O4(O2CMe)4(py)4 (1a, py = pyridine derivatives), serves as a homogeneous molecular co-catalyst which is engineered into the framework of pristine polymeric carbon nitride (PCN) for water oxidation with light illumination. This modification strategy maximizes the contact areas between co-catalysts and reactants, reduces the over-potential of oxygen producing and accelerates the interface transfer rate of electron-hole pairs, thus leading to enhanced reaction kinetics for photocatalytic water oxidation. Compared with pristine PCN, the photocatalytic O2 production rate up to 19-fold-enhanced in the presence of molecular co-catalyst. This work emphasizes the importance of developing effective, stable and earth-abundant molecular co-catalysts for the promotion of water-splitting photocatalysis.

Kagóme Cobalt(II)-Organic Layers as Robust Scaffolds for Highly Efficient Photocatalytic Oxygen Evolution.

Two Kagóme cobalt(II)-organic layers of [Co3 (μ3 -OH)2 (bdc)2 ]n (1) and [Co3 (μ3 -OH)2 (chdc)2 ]n (2) (bdc=o-benzenedicarboxylate and chdc=1,2-cyclohexanedicarboxylate) that bear bridging OH(-) ligands were explored as water oxidation catalysts (WOCs) for photocatalytic O2 production. The activities of 1 and 2 towards H2 O oxidation were assessed by monitoring the in situ O2 concentration versus time in the reaction medium by utilizing a Clark-type oxygen electrode under photochemical conditions. The oxygen evolution rate (RO2 ) was 24.3 μmol s(-1) g(-1) for 1 and 48.8 μmol s(-1) g(-1) for 2 at pH 8.0. Photocatalytic reaction studies show that 1 and 2 exhibit enhanced activities toward the oxidation of water compared to commercial nanosized Co3 O4 . In scaled-up photoreactions, the pH value of the reaction medium decreased from 8.0 to around 7.0 after 20 min and the O2 production ceased. Based on the amounts of the sacrificial oxidant (K2 S2 O8 ) used, the yield of O2 produced is 49.6 % for 2 and 29.8 % for 1. However, the catalyst can be recycled without a significant loss of catalytic activity. Spectroscopic studies suggest that the structure and composition of recycled 1 and 2 are maintained. In isotope-labeling H2 (18) O (97 % enriched) experiments, the distribution of (16) O(16) O/(16) O(18) O/(18) O(18) O detected was 0:7.55:92.45, which is comparable to the theoretical values of 0.09:5.82:94.09. This work not only provides new catalysts that resemble ligand-protected cobalt oxide materials but also establishes the significance of the existence of OH(-) (or H2 O) binding sites at the metal center in WOCs.

Synthesis of Ordered Mesoporous CuO/CeO₂ Composite Frameworks as Anode Catalysts for Water Oxidation.

Cerium-rich metal oxide materials have recently emerged as promising candidates for the photocatalytic oxygen evolution reaction (OER). In this article, we report the synthesis of ordered mesoporous CuO/CeO2 composite frameworks with different contents of copper(II) oxide and demonstrate their activity for photocatalytic O2 production via UV-Vis light-driven oxidation of water. Mesoporous CuO/CeO2 materials have been successfully prepared by a nanocasting route, using mesoporous silica as a rigid template. X-ray diffraction, electron transmission microscopy and N2 porosimetry characterization of the as-prepared products reveal a mesoporous structure composed of parallel arranged nanorods, with a large surface area and a narrow pore size distribution. The molecular structure and optical properties of the composite materials were investigated with Raman and UV-Vis/NIR diffuse reflectance spectroscopy. Catalytic results indicated that incorporation of CuO clusters in the CeO2 lattice improved the photochemical properties. As a result, the CuO/CeO2 composite catalyst containing ~38 wt % CuO reaches a high O2 evolution rate of ~19.6 µmol·h−1 (or 392 µmol·h−1·g−1) with an apparent quantum efficiency of 17.6% at λ = 365 ± 10 nm. This OER activity compares favorably with that obtained from the non-porous CuO/CeO2 counterpart (~1.3 µmol·h−1) and pure mesoporous CeO2 (~1 µmol·h−1).

Ni2+ doped InVO4 nanocrystals: One-pot microwave-assisted synthesis and enhanced photocatalytic O2 production activity under visible-light

In this letter, Ni2+ doped InVO4 nanocrystals were successfully synthesized by a simple one-pot microwave-assisted method. The energy bandgap of obtained samples can be precisely controlled by varying the Ni2+ doping amount. The O2 production rate of obtained Ni–InVO4 nanocrystals is higher than that of pure InVO4 nanocrystals under visible-light, which can be ascribed to the narrowed band gaps. The corresponding 1% doped sample N1 has the highest O2 production rate (394μmol/h) in all samples, which is 66% higher than the undoped sample N0.

Hydrothermal synthesis and visible-light-driven oxygen production from water splitting of InVO 4 micron–rods

A new type of InVO4 micron–rods photocatalyst was successfully synthesised by a facile additive-assisted hydrothermal method as a novel O2 evolution photocatalyst. The as-obtained micro–rods are well-crystallised with about 2 μm lengths and 500 nm widths. In the authors system, the sodium dodecyl sulfate amount, as well as the reaction time and temperature, plays an important role in the formation of the InVO4 micronrods. From the UV–vis absorption spectrum, the bandgap energy of as-obtained InVO4 microrods is 2.3 eV. Under visible-light irradiation, InVO4 microrods show excellent photocatalytic O2 production activity (2.663 mmol h−1 g−1) with AgNO3 as sacrifice reagents.