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Addressing the escalating concerns over increasing carbon dioxide (CO2) emissions and their detrimental effect on the environment has become global attention. One promising alternative to tackle this issue involves utilizing photocatalytic technology to convert CO2 into more valuable chemicals, with methane (CH4) being a notable targeted product. This article presents a comprehensive review of the exploration of TiO2‐based photocatalysts by researchers worldwide for such applications. The initial discussion revolves around fundamental aspects, including the basic principles, thermodynamics, kinetics, and reaction mechanisms involved in the process. Additionally, to enhance the efficiency of these aspects, support from other factors is necessary, including the physicochemical properties of the photocatalyst through various catalyst synthesis methods (such as sol‐gel, precipitation, hydrothermal, and solvothermal) as well as employing catalyst modification techniques (such as doping, heterojunction, and surface modifications). Furthermore, the review delves into an examination of parameters that influence the photocatalytic CO2 reduction to methane process, as they directly impact the yield and selectivity of the desired product. Ultimately, the existing challenges and potential research opportunities that could provide comprehensive solutions for the applications of photocatalytic technology for converting CO2 to CH4 as a whole are elaborated in this review. [ABSTRACT FROM AUTHOR]

A series of nitrogen‐doped TiO2 were prepared through a simple sol‐solvothermal method. The catalysts were characterized by BET, XRD, SEM‐EDS, Raman, XPS, FTIR, UV‐Vis, etc. The results show that N−TiO2 photocatalyst has a larger specific surface area, stable anatase phase, and narrow forbidden band energy (3.17–3.24 eV). The N‐doped TiO2 has more oxygen vacancies (OVs) than pure TiO2, as confirmed by results such as XPS and ESR. The photocatalytic evaluation results show that the decolorization of methyl orange reached 99.03 % over the 3 % N‐doped TiO2, which is 40 % higher than that of pure TiO2. Meanwhile, 3 % N‐doped TiO2 exhibited a faster MO mineralisation rate than TiO2. After repeatedly used for 5 times, the photocatalyst 3‐N−TiO2 still showed high activity in the degradation of MO. The improvement of the visible light performance of the N−TiO2 photocatalyst could be attributed to the introduction of N in TiO2 to generate new N 2p energy levels and rich OVs. [ABSTRACT FROM AUTHOR]

TiO2 photocatalysis, as an energy‐saving, high‐efficiency and green technology, has a wide range of applications in sewage treatment, cancer treatment, hydrogen production, photocatalytic CO2 reduction and photocatalytic sensors. However, the large band width (Eg=3.2 eV) of TiO2 material hinders its practical application, which in turn leads to low visible‐light utilization and low quantum yield. Therefore, the preparation of TiO2 with high quantum yield and fast response to visible light has become a key topic in current photocatalyst research. This review discusses different photocatalytic applications, current synthetic techniques for the elaboration of nanostructures of several TiO2‐based materials and recent advances in enhancing visible photocatalytic activity. [ABSTRACT FROM AUTHOR]

Titanium dioxide is an essential photocatalyst for the purification of water and air and energy generation. Titanium dioxide shows relatively high chemical stability and reactivity under ultraviolet light (λ< 387 nm), the energy of which exceeds the 3.3 eV bandgap in the crystalline anatase phase. TiO2 is active under UV light, and its practical applicability is limited under visible light. Modification techniques like metal doping can enhance its activity under visible light. Metal doping is employed for introducing additional states in the TiO2 bandgap. Fewer energy transitions are required to cause visible light absorption by these impurities. This review focuses on the effects of metal‐doping and applications of metal‐doped TiO2 in the fields of environmental remediation, hydrogen evolution, and sensing. [ABSTRACT FROM AUTHOR]

With their unique optical and electronic properties, carbon dots (CDs) are showing great momentum in many fields such as biosensing, imaging, drug delivery, and photocatalysis. Due to their efficient light harvesting, extraordinary upconversion photoluminescence, and excellent photoinduced electron transfer capabilities, the combination of CDs with photocatalytic materials will promote light absorption resulting in increased generation of electron‐hole pairs and faster photogenerated electron transfer, effectively suppressing the rate of electron‐hole pair complexation and thus improving photocatalytic activity. In this paper, the mechanism of CDs photocatalysis and various photocatalytic materials such as TiO2, Bi‐based, CdS, and g‐C3N4 complexed with CDs are reviewed. It is hoped that research into CDs in the field of photocatalysis will be advanced and that CDs will be used more widely in environmental and energy applications. [ABSTRACT FROM AUTHOR]

Solar‐driven semiconductor photocatalysis shows great potential to solve growing energy and environmental crises. Electrospun TiO2 nanofibers (NFs) attract attention due to their chemical stability, nontoxicity, cheapness, large specific surface area, and porous structures. The unique unwoven nanofibrous network facilitates mass transportation compared with bulk materials. Electrospun TiO2 NFs are an ideal substrate for growing secondary nanostructures and constructing heterojunction photocatalysts. The hybrid heterojunctions show enhanced electron–hole separation, improved light absorption, effective activation of reactants, and therefore increased photocatalytic performance. Herein, the electrospinning principle and preparing tactics of electrospun TiO2 fibrous nanostructures including solid, hollow, and core/shell NFs are first described. The construction strategies of electrospun TiO2‐based heterojunctions by loading electron or hole cocatalysts and hybridizing secondary semiconductors to engineer catalytic active sites and steer charge carrier separation are outlined. Dopant‐induced increased light absorption and enhanced charge transfer of TiO2 NFs are discussed. Further, the applications of electrospun TiO2‐based photocatalysts for solar‐to‐chemical conversion and environmental remediation are elucidated. Finally, the challenges and perspectives for the development of electrospun TiO2‐based photocatalysts are underlined, which deepen a systematic understanding of the design and fabrication of more efficient electrospun NFs in the future. [ABSTRACT FROM AUTHOR]

Lignin, an underutilized component of lignocellulosic biomass, is regarded as a rich reservoir for the production of aromatic chemicals and fuels. Despite extensive research in recent years, lignin's potential is far from being fully unlocked. Photocatalysis that uses sustainable solar energy to drive lignin conversion under mild conditions has been identified as a promising strategy and received growing research interest. This review aims to present a critical introduction to the photocatalytic conversion of lignin, including a summary of lignin conversion pathways and mechanisms, as well as the latest cutting‐edge innovations on photocatalyst design and reactor construction. Moreover, the screening of solvents and regulation of other key factors that are involved in photocatalytic lignin conversion are also elucidated and future perspectives and challenges for photocatalytic conversion of lignin into valuable products are discussed. [ABSTRACT FROM AUTHOR]

Novel BiOF/TiO2 heterostructures with controlled amounts of BiOF and TiO2 have been successfully synthesized via a simple solid‐state sintering method. The structural, morphological and optical properties were analyzed using several characterization techniques. A shift of the TiO2 absorption edge toward the visible region was observed. The optimal molar ratio of BiOF/TiO2 was found to be (1:3) with a photodegradation percentage of 91.2 % and it was 7 and 5 times more efficient than that of pure BiOF or TiO2 nanopowder, respectively. BiOF/TiO2 (1:3) heterojunction has showed high photodegradation stability for the Rh B photodegradation after three cycles. In the proposed photocatalytic mechanism, TiO2 absorbed the visible light and carried out the photocatalytic reaction owing to the decrease of its band gap value due to the formation of oxygen vacancies, while BiOF played an important role in the charge separation process due to the intimate contact of the BiOF/TiO2 heterojunction. [ABSTRACT FROM AUTHOR]

One‐dimensional (1D) nanostructured photocatalyst is a promising candidate for hydrogen (H2) generation, which can be used to deal with the energy crisis. Herein, novel 1D TiO2/CdS well‐hybridized nanofibers (NFs) were synthesized via in situ electrospinning method. These 1D hybrid NFs showed a high H2‐production rate of 2.32 mmol h−1 g−1 with an apparent quantum efficiency of 10.14 %, which was 35‐fold higher than that of pristine TiO2 NFs. X‐ray photoelectron spectroscopy (XPS) analysis and density functional theory calculation implied that the electrons transferred from CdS to TiO2 upon hybridization and created an internal electric field (IEF) pointing from CdS to TiO2. This IEF drove the photoexcited electrons in TiO2 to transfer toward CdS upon light irradiation as revealed by in situ irradiated XPS analysis, suggesting that a step‐scheme (S‐scheme) heterojunction was formed in the TiO2/CdS nanohybrids and greatly promoted the separation of electron‐hole pairs to foster efficient H2 photogeneration. The significant enhancement of photocatalytic activity was also benefited from the easy transfer for electrons in the 1D well‐distributed nanostructure of nanohybrids. This work presents a method for in situ preparing well‐distributed 1D NFs with high photocatalytic activity for H2 production via the S‐scheme pathways. [ABSTRACT FROM AUTHOR]

Ag/mesoporous black TiO2 nanotubes heterojunctions (Ag‐MBTHs) were fabricated through a surface hydrogenation, wet‐impregnation and photoreduction strategy. The as‐prepared Ag‐MBTHs possess a relatively high specific surface area of ≈85 m2 g−1 and an average pore size of ≈13.2 nm. The Ag‐MBTHs with a narrow band gap of ≈2.63 eV extend the photoresponse from UV to the visible‐light and near‐infrared (NIR) region. They exhibit excellent visible‐NIR‐driven photothermal catalytic and photocatalytic performance for complete conversion of nitro aromatic compounds (100 %) and mineralization of highly toxic phenol (100 %). The enhancement can be attributed to the mesoporous hollow structures increasing the light multi‐refraction, the Ti3+ in frameworks and the surface plasmon resonance (SPR) effect of plasmonic Ag nanoparticles favoring light‐harvesting and spatial separation of photogenerated electron–hole pairs, which is confirmed by transient fluorescence. The fabrication of this SPR‐enhanced visible‐NIR‐driven Ag‐MBTHs catalyst may provide new insights for designing other high‐performance heterojunctions as photocatalytic and photothermal catalytic nanomaterials. Responding strongly: Ag/mesoporous black TiO2 hollow nanotube heterojunctions with wide‐spectrum response (≈2500 nm) were fabricated through a wet‐impregnation and photoreduction strategy. They exhibit excellent visible‐NIR‐driven photocatalytic and photothermal catalytic performance and long‐term stability, due to the synergistic effect of efficient surface hydrogenation, hollow structured TiO2, formation of heterojunctions, and surface plasmon resonance of Ag. [ABSTRACT FROM AUTHOR]

Molybdenum trioxide (MoO3) represented an excellent photocatalytic performance with many applications, including degradation of organic contaminants and splitting of water. This paper presented a new route to synthesize MoO3 nanobelts with high aspect ratios and crystallinity by a hydrothermal technique. This work showed that the as‐synthesized nanobelts exhibited strong photocatalytic activity to degrade an organic dye of Rhodamine B (RhB) in aqueous solution under the exposure of the light source in the near infrared wavelength range, significantly improving the photocatalytic activity of the nanobelts. The results also showed that for a small concentration of RhB at 7.5 mg/L a complete photodegradation (for a given MoO3 nanobelts quantity of 0.1 g) can be reached after exposing for 60 min. For all concentrations of the RhB solution, the photodegradation exhibited an exponential dependence on the exposure time followed by a sudden shutdown, but no complete photodegradation can be reached. Also, the residual quantity of RhB in solution after the photocatalytic reaction was determined by the initial RhB concentration. The photocatalytic degradation can be interpreted by the pseudo–first‐order equation for the absorption of liquid/solid based on solid capacity; thus, photocatalytic degradation can be attributed to the interaction between the photoexcited electrons in the substrate and the antibonding orbital of the RhB in solution. The sudden shutdown was due to the inability of the photoexcited electrons in the substrate hopping to the antibonding orbital of RhB in the presence of the RhB intermediate products from the degraded RhB. In addition, this work showed that the photocatalytic reaction can be recovered after a thermal treatment of postreacted MoO3 nanobelts, enhancing the utilization efficiency of the catalysis. [ABSTRACT FROM AUTHOR]

Degradation of oxalic acid on particulate TiO2, ZnO, CuO, Bi2O3, In2O3, and Nb2O5 under UV-A light exhibits first-order kinetics, and the degradation rates increase linearly with the photon flux. All the oxides show sustainable photocatalytic activity, and the photonic efficiencies of degradation of oxalate are very much lower than those of the acid. The ease of degradation of carboxylic acids is the following: formic > oxalic > acetic > citric. Intimate mixtures of two different particulate semiconductors kept under suspension and at continuous motion exhibit higher photocatalytic activity, revealing interparticle charge transfer. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 716–726, 2009 [ABSTRACT FROM AUTHOR]