Photo-induced CO2 Research Articles

Photoinduced Carbon Dioxide Release via a Metastable Photoacid in a Nonaqueous Environment.

Capturing carbon dioxide (CO2) from the atmosphere is a scientific and technological challenge. CO2 can be captured by forming carbamate bonds with amines, most notably monoethanolamine (MEA). Regenerating MEA by releasing captured CO2 requires that the carbamate solution be heated. Recently, photoacids were used to induce a pH change to release CO2 from aqueous carbonate solutions. We report a merocyanine photoacid that releases CO2 from nonaqueous carbamate solutions of MEA, which has a CO2 loading capacity that is higher than that of water. On the basis of the absorption spectra of the photoacid in the presence of acids and CO2, we show that the photoacid cycle and the CO2 capture of MEA are two separate equilibria coupled to each other via protons. We demonstrate that irradiating the sample with 405 nm light induces the release of CO2, which we detect using an in-line mass spectrometer. This work highlights an alternative path for optimizing a photoinduced CO2 capture and release system.

Time-Resolved Mechanistic Depiction of Photoinduced CO2 Reduction Catalysis on a Urea-Modified Iron Porphyrin.

The development of functional artificial photosynthetic devices relies on the understanding of mechanistic aspects involved in specialized photocatalysts. Modified iron porphyrins have long been explored as efficient catalysts for the light-induced reduction of carbon dioxide (CO2) towards solar fuels. In spite of the advancements in homogeneous catalysis, the development of the next generation of catalysts requires a complete understanding of the fundamental photoinduced processes taking place prior to and after activation of the substrate by the catalyst. In this work, we employ a state-of-the-art nanosecond optical transient absorption spectroscopic setup with a double excitation capability to induce charge accumulation and trigger the reduction of CO2 to carbon monoxide (CO). Our biomimetic system is composed of a urea-modified iron(III) tetraphenylporphyrin (UrFeIII) catalyst, the prototypical [Ru(bpy)3]2+ (bpy=2,2'-bipyridine) used as a photosensitizer, and sodium ascorbate as an electron donor. Under inert atmosphere, we show that two electrons can be successively accumulated on the catalyst as the fates of the photogenerated UrFeII and UrFeI reduced species are tracked. In the presence of CO2, the catalytic cycle is kick-started providing further evidence on CO2 activation by the UrFe catalyst in its formal FeI oxidation state.

Photo-induced CO2 cycloaddition and tetracycline degradation over novel FeOx modified defective graphitic carbon nitride composite

Utilizing sunlight to achieve CO2 conversion and environmental remediation has been a key focus. Herein, “all-in-one” graphitic carbon nitride (g-C3N4) composite-based photocatalysts were synthesized by a simple one-step low-temperature calcination. Lower calcination temperature resulted in defective g-C3N4 enriched in cyano and hydroxyl groups. It was found that by incorporating amorphous FeOX, the resulted FeOX/O-g-C3N4 photocatalyst shows very good performance towards both CO2 cycloaddition reaction and photo-Fenton degradation of tetracycline (TC). It was also found that the photocatalyst shows the highest styrene carbonate yield of 83% (23 mmol g−1 h−1) under ambient conditions, which is 13.8 times higher than that obtained over pure g-C3N4. The photocatalyst also exhibits a 4.7 times faster TC removal rate than that of pure g-C3N4. Systematic characterization and mechanism study demonstrate the role of defects and photo-induced charge carriers.

The slow photo-induced CO2 release of N-phthaloylglycine

As time-resolved infrared spectroscopy shows, the title compound undergoes photo-induced CO2 release within microseconds – orders of magnitudes longer than anticipated.

Biomass derived ZnO/N-doped porous carbon for photo-induced CO2 cycloaddition

Accumulation of atmospheric CO2 poses a serious threat to the global environment, but there is still a lack of effective CO2 catalytic conversion under mild conditions. Herein, multifunctional ZnO/N-doped porous carbon materials, ZNPC-X, were fabricated by pyrolysis of available pine pollen with melamine and zinc chloride. The optimized ZNPC-600 produced at 600 °C can work as an efficient photothermal catalyst towards CO2 cycloaddition conversion with a high catalytic yield of 99% under mild conditions (0.3 W/cm2, 1 bar). Moreover, ZNPC-600 shows excellent recyclability after ten cycles and desirable performance even under simulated flue gas and after moisture treatment. Absorption spectra and time-dependent infrared images unveil that the intrinsically broad light absorption and high photothermal conversion efficiency are the major reasons for the high activity of ZNPC-600. Besides, photogenerated electrons can be transferred to CO2 and activate it, while photogenerated holes can be used as Lewis acid to facilitate the ring opening of epoxides. In addition, the hierarchical pore structure and the synergy between ZnO and pyridine N also play a role in the mass transfer and activation of epoxides and CO2, respectively. This work provides a low-cost and facile solution to obtain catalysts derived from biomass for promoting CO2 conversion.

Amine Hole Scavengers Facilitate Both Electron and Hole Transfer in a Nanocrystal/Molecular Hybrid Photocatalyst

A well-known catalyst, fac-Re(4,4'-R2-bpy)(CO)3Cl (bpy = bipyridine; R = COOH) (ReC0A), has been widely studied for CO2 reduction; however, its photocatalytic performance is limited due to its narrow absorption range. Quantum dots (QDs) are efficient light harvesters that offer several advantages, including size tunability and broad absorption in the solar spectrum. Therefore, photoinduced CO2 reduction over a broad range of the solar spectrum could be enabled by ReC0A catalysts heterogenized on QDs. Here, we investigate interfacial electron transfer from Cd3P2 QDs to ReC0A complexes covalently bound on the QD surface, induced by photoexcitation of the QD. We explore the effect of triethylamine, a sacrificial hole scavenger incorporated to replenish the QD with electrons. Through combined transient absorption spectroscopic and computational studies, we demonstrate that electron transfer from Cd3P2 to ReC0A can be enhanced by a factor of ∼4 upon addition of triethylamine. We hypothesize that the rate enhancement is a result of triethylamine possibly altering the energetics of the Cd3P2-ReC0A system by interacting with the quantum dot surface, deprotonation of the quantum dot, and preferential solvation, resulting in a shift of the conduction band edge to more negative potentials. We also observe the rate enhancement in other QD-electron acceptor systems. Our findings provide mechanistic insights into hole scavenger-quantum dot interactions and how they may influence photoinduced interfacial electron transfer processes.

Designing dual-atom cobalt catalysts anchored on amino-functionalized MOFs for efficient CO2photoreduction

Binuclear Co2-MOF(–NH2) catalyst outperformed its mononuclear counterpart by 10.5 times with a CO yield of 2.44 mmol gCo−1h−1. This highlights the enhanced photoinduced CO2 reduction through synergistic catalysis at two Co sites.

Photoinduced CO2 and N2 reductions on plasmonically enabled gallium oxide

Ag-containing ZnO/ β-Ga2O3 semiconductor, which exhibit reduced bandgap, increased light absorption, and hydrophilicity, have been found to be useful for photocatalytic CO2 reduction and N2 fixation by water. The charge-separation is facilitated by the new interfaces and inherent vacancies. The Ag@GaZn demonstrated the highest photocurrent response, about 20- and 2.27-folds that of the Ga and GaZn samples, respectively. CO, CH4, and H2 formed as products for photo-reduction of CO2. Ag@GaZn catalyst exhibited the highest AQY of 0.121 % at 400 nm (31.2 W/m2). Also, Ag@GaZn generated 740 μmolg-1 of NH4+ ions, which was about 18-folds higher than Ga sample. In situ DRIFTS for isotopic-labelled 13CO2 and 15N2 reaffirmed the photo-activity of as-synthesized catalysts. Density functional theory provided insight into the relative affinity of different planes of heterostructures towards H2O, CO2 and N2 molecules. The structure-photoactivity rationale behind the intriguing Ag@GaZn sample offers a fundamental insight into the role of plasmonic Ag and design principle of heterostructure with improved photoactivity and stability.

Graphene/inorganic nanocomposites: Evolving photocatalysts for solar energy conversion for environmental remediation

Current energy crisis and environmental issues, including depletion of fossil fuels, rapid industrialization, and undesired CO2 emission resulting in global warming has created havoc for the global population and significantly affected the quality of life. In this scenario the environmental problems in the forefront of research priorities. Development of renewable energy resources particularly the efficient conversion of solar light to sustainable energy is crucial in addressing environmental problems. In this regard, the synthesis of semiconductors-based photocatalysts has emerged as an effective tool for different photocatalytic applications and environmental remediation. Among different photocatalyst options available, graphene and graphene derivatives such as, graphene oxide (GO), highly reduced graphene oxide (HRG), and doped graphene (N, S, P, B-HRG) have become rising stars on the horizon of semiconductors-based photocatalytic applications. Graphene is a single layer of graphite consisting of a unique planar structure, high conductivity, greater electron mobility, and significantly very high specific surface area. Besides, the recent advancements in synthetic approaches have led to the cost-effective production of graphene-based materials on a large-scale. Therefore, graphene-based materials have gained considerable recognition for the production of semiconducting photocatalysts involving other semiconducting materials. The graphene-based semiconductors photocatalysts surpasses electron-holes pairs recombination rate and lowers the energy band gap by tailoring the valence band (VB) and conduction band (CB) leading to the enhanced photocatalytic performance of hybrid photocatalysts. Herein, we have summarized the latest developments in designing and fabrication of graphene-based semiconducting photocatalysts using a variety of commonly applied methods such as, post-deposition methods, in-situ binding methods, hydrothermal and/or solvothermal approaches. In addition, we will discuss the photocatalytic properties of the resulting graphene-based hybrid materials for various environmental remediation processes such as; (i) clean H2 fuel production, photocatalytic (ii) pollutants degradation, (iii) photo-redox organic transformation and (iv) photo-induced CO2 reduction. On the whole, by the inclusion of more than 300 references, this review possibly covered in detail the aspects of graphene-based semiconductor photocatalysts for environmental remediation processes. Finally, the review will conclude a short summary and discussion about future perspectives, challenges and new directions in these emerging areas of research.

Photo-induced photo-thermal synergy effect leading to efficient CO2 cycloaddition with epoxide over a Fe-based metal organic framework

It is crucial to design and synthesize a catalyst that can catalyze the production of cyclic carbonates from CO2 and epoxide under mild conditions. Herein, we successfully synthesized a two-dimensional metal organic framework FeTPyP, which displays an outstanding capability to catalyze the CO2 cycloaddition reaction under light irradiation with a yield of styrene carbonate as high as 106.13 mmol/(g h). Characterizations suggests that the major reason is due to (1) the synergistic effect between photocatalysis and thermocatalysis and (2) ultraviolet light can promote the ring-opening reaction of styrene oxide. This work provides an alternative approach to further design efficient heterogeneous catalysts for photo-induced CO2 cycloaddition reaction via coupling thermocatalysis and photocatalysis.

Photo-induced carbon dioxide reduction on hexagonal tungsten oxide via an oxygen vacancies-involved process

Although converting the greenhouse gasses carbon dioxide (CO2) into solar fuels is regarded as a convenient means of solar energy storage, the intrinsic mechanism on how the high chemical inertness linear CO2 molecules is activated and converted on a semiconductor oxide is still elusive. Herein, by creating the oxygen vacancies on the typical hexagonal tungsten oxide (WO3), we realize the continuous photo-induced CO2 reduction to selectively produce CO under light irradiation, which was verified by isotope labeling experiment. Detailed oxygen vacancies evolution investigation indicates that light irradiation can simultaneously induce the in-situ formation of oxygen vacancies on hexagonal WO3, and the oxygen vacancies promote the adsorption and activation of CO2 molecules, leading to the CO2 reduction to CO on the hexagonal WO3via an oxygen vacancies-involved process. Besides, the existence of water further promotes the formation of CO2 reduction intermediate, further promote the CO2 photoreduction. Our work provides insight on the mechanism for converting CO2 into CO under light irradiation.

Highly stable LaCoO3 perovskite supported g-C3N4 nanotextures with proficient charges migration for visible light CO2 photoreduction to CO and CH4

Z-scheme LaCoO3/g-C3N4 heterojunction, synthesized via a facile one-step wet impregnation process, has been investigated for photoinduced CO2 reduction to CO and CH4. The LaCoO3 was uniformly dispersed with g-C3N4 nanotexture to construct heterojunction with proficient electron-hole separation due to good interfacial interaction. The photocatalytic CO2 reduction reveals highest CO evolution over 15% LaCoO3 loaded g-C3N4 with yield rate 135.2 μmol g−1h−1, which is 1.2 and 1.18 folds-higher than using pristine LaCoO3 and g-C3N4 samples, respectively. Similarly, in comparison to LaCoO3 and g-C3N4, using LaCoO3/g-C3N4, CH4 evolution of 1.7 and 1.59 folds higher was achieved. This significantly enhanced productivity toward CO and CH4 was evidently due to good interface interaction with higher light absorption and fascinating separation of charge carrier. Among the operating parameters, highest photoactivity for CO and CH4 production was achieved at lower catalyst loading, which confirms higher light utilization to promote quantum yield of the products. This further confirms that mass transfer and catalyst exposed to light irradiations are the determinable factors to promote efficiency. Furthermore, Z-scheme LaCoO3/g-C3N4 composite exhibits excellent stability in consecutive three cycles. This research provides pathways to construct composite photocatalyst with high-performance and stability, thus would also be useful for other solar energy applications.

A novel N-doped graphene oxide enfolded reduced titania for highly stable and selective gas-phase photocatalytic CO2 reduction into CH4: An in-depth study on the interfacial charge transfer mechanism

A desire for renewable alternatives to fossil fuels can be achieved by utilizing CO2, H2O, and solar energy to generate solar fuels. A novel N-doped graphene oxide enfolded reduced titania (NGO-RT) composite was demonstrated for photocatalytic CO2 reduction into CH4. Later, a small amount of Pt NPs was deposited on NGO-RT that increases the catalytic performance towards CH4 formation. The optimized Pt1.0%-NGO-RT catalyst displayed a selective visible-light CO2 reduction into CH4 using a flow reactor system with ≈12 and ≈2 times higher activity than pristine RT and NGO-RT, respectively. The catalyst demonstrated long-term stability over 35 h. The photo-induced CO2 reduction mechanism was first validated through the electron transfer process, where charge trapping by Ti3+ states near the conduction band of RT plays a vital role in the selective CH4 evolution. These trapped electrons transfer from RT to the closely connected interface of N-doped graphene oxide and Pt NPs to restrict the recombination of electron/hole pair. The improved catalytic performance can be attributed to RT’s downward band bending at the NGO-RT interface, where electron transfer from RT to NGO decreases the charge recombination.

Photoreduction of CO2 in the presence of CH4 over g-C3N4 modified with TiO2 nanoparticles at room temperature

CO2 reduction under simulated sunlight over photocatalysts has become an attractive researcher area recently. In this work, carbon nitride compounds modified by TiO2 nanoparticles (TNPs) have been used for the photoreduction of CO2 in the presence of CH4 at room temperature. Briefly, a series of noble-metal-free TNP-graphitic-carbon nitride (g-C3N4, also abbreviated CN) photocatalysts with different TNPs loadings and calcination temperatures have been synthesized by a wet-chemical method. The characterization results of XRD, FTIR, SEM, TEM, BET, XPS, CO2 Adsorption, UV-vis, and PL demonstrate that the BET surface area and CO2 adsorption capacity have been improved after the calcination. Besides, the g-C3N4 has been successfully coupled with the TNPs and a heterojunction has formed at their interface. These characters contribute to increase the photocatalytic activity of TNPs-CN toward reducing CO2 in the presence of CH4, and its’ performance is better than bare g-C3N4, Titania (P25)–CN, MgO–CN, or Cu2O–CN. Orthogonal experiments are then carried out to investigate the sensitivity factors and optimum conditions. The sensitivity results show that the reaction pressure makes little difference on the photocatalysis results, which verifies the photoinduced CO2–CH4 reaction has a tiny change in gas volume. In addition, under the optimum conditions, the turnover frequency (TOF) of CO after 4 h reaction can reach 9.98 μmol g-cat.−1 h−1, and traces of ethane and ethylene have been detected during the reactions. In addition, surface acetate and carbonaceous deposit are found on the (20)TNPs-CN/450 surface after continuous 24 h irradiation under the optimum conditions, which resulting in the inactivation of the catalyst. Finally, possible reaction mechanisms have been proposed based on the results.

2D/2D/2D O-C3N4/Bt/Ti3C2Tx heterojunction with novel MXene/clay multi-electron mediator for stimulating photo-induced CO2 reforming to CO and CH4

Controlled fabrication of Ti3C2 MXene with unique topology and layered bentonite (Bt) nanoclay to construct a 2D/2D/2D g-C3N4/Bt/Ti3C2 MXene heterojunction for intriguing photocatalytic CO2 reduction has been investigated. The MXene/Bt composite exhibits high-light absorption and faster charges separation and transportation. The photoactivity of 2D/2D Ti3C2/g-C3N4 of 1.38 folds higher than bulk Ti3AlC2/g-C3N4 obtained due to intimate interface interaction with proficient charges separation. The highest g-C3N4/Bt/Ti3C2 heterojunction activity for CH4 evolution of 4.18, 4.42 and 6.96 folds more was achieved compared with g-C3N4/Ti3C3, Bt/g-C3N4 and g-C3N4, respectively. This boosted activity was evidently due to Ti3C2/g-C3N4 Schottky junction with Bt-mediator to provide new electron transfer channels. More interestingly, with proton rich acetic-acid reagent, 4.15 folds more CH4 production than using only water under prolonged stability was observed. Thus, this study provides a promising approach for clean energy system and potential applications of MXenes/Bt materials for solar fuels production.

Photoinduced Dry and Bireforming of Methane to Fuels over La‐Modified TiO2 in Fixed‐Bed and Monolith Reactors

A systematic investigation on the performance of fixed‐bed and monolithic reactors for dynamic photoinduced CO2 reduction with CH4 via dry and bi‐reforming of methane over La‐modified TiO2 nanocatalyst under UV light is conducted. La/TiO2 is synthesized using a modified sol–gel method, and the monolithic‐coated catalyst is synthesized using a dip‐coating method. The performance of La/TiO2 is tested for different reforming systems in both types of photoreactors. The results reveal 5 wt% La/TiO2 effectively promotes CO2 and CH4 conversion to CO, H2, and C2H6, whereas catalyst performance is greatly enhanced in the presence of H2O in both types of reactors via bireforming of methane (BRM). Lower temperature is favorable for CO production, whereas H2 and C2H6 yields are enhanced at higher temperature. Notably, the monolith photoreactor is favorable for enhanced CO and H2 yields. More interestingly, quantum yield (QY) for H2 in BRM using monolith photoreactor is 1.402%—an increment of almost 4.99‐fold than dry reforming of methane (DRM). This can be attributed to enhanced CO2 adsorption with hindered charge recombination by La, appropriate redox potentials, larger illuminated surface area, and higher photon flux. The prolonged La/TiO2 activity in a monolith photoreactor for enhanced CO and H2 production signifies its potential for CO2 conversion applications.

Indirect Z-Scheme Assembly of 2D ZnV2O6/RGO/g-C3N4 Nanosheets with RGO/pCN as Solid-State Electron Mediators toward Visible-Light-Enhanced CO2 Reduction

Indirect Z-scheme assembly of graphene-bridged 2D ZnV2O6/pCN nanosheets composite has been fabricated by one-step solvothermal process and tested for photoinduced CO2 conversion under visible-light irradiations. The highest CH3OH production of 3488 μmol g-cat–1 was obtained over ZnV2O6/RGO/g-C3N4 composite, 1.02 and 1.25 times higher comparing to ZnV2O6/RGO and ZnV2O6/g-C3N4 samples, respectively. This enhanced efficiency can be ascribed to well-designed ternary heterojunction with hierarchical structure and efficient charges separation by RGO. More importantly, CH3OH yield was further improved by introducing RGO/pCN as an electron sink, which led to a 1.07 times higher yield than using only RGO. This reveals that ternary 2D ZnV2O6/RGO/pCN nanostructure has higher visible-light absorption, improved charge separation, and enhanced photocatalytic efficiency due to RGO/pCN as multiple mediators. The stability of composite catalyst also prevailed for 32 h for continuous CH3OH production. Therefore, structured...

Photophysical and electrochemical properties of [Re(CO)3Cl(NN)] (NN = dppp3, dppp2, dppp2Br) complexes functionalised with pendant pyridyl ligands

We report the synthesis, electrochemical, and photophysical properties of a series of rhenium complexes, [Re(CO)3Cl(NN)] (NN = dppp2, dppp3, and dppp2Br; dppp2 = pyrido[2′,3′:5,6]pyrazino[2,3-f][1,10]phenanthroline, dppp3 = pyrido[3′,4′:5,6]pyrazino[2,3-f][1,10]phenanthroline, dppp2Br = 8-bromopyrido[2′,3′:5,6]pyrazino[2,3-f][1,10]phenanthroline), which have potential for use as CO2 photoreduction catalysts. The complexes are related to [Re(CO)3Cl(dppz)] (dppz = dipyrido[3,2-a:2′,3′-c]phenazine) but have an additional nitrogen heteroatom in the distal phenazine (phz) aromatic ring of the dppz ligand which is known to promote potential photoinduced CO2 binding and reduction in related complexes. We use Fourier transform infrared (FTIR), UV/Visible, electron paramagnetic resonance (EPR) and time-resolved infrared (TRIR) spectroscopies to investigate how the location of the additional nitrogen atom, and how the nature of the substituents affects the photophysical properties. In addition, the one electron reduced catalysts are generated following bulk electrochemical reduction and characterised in CH2Cl2. TRIR experiments in d6-DMSO, CH3CN, CH2Cl2, THF and toluene reveal that excitation generates a 3MLCT(phz) (phz = phenazine) excited state in all compounds. In CH3CN and d6-DMSO (not for [Re(CO)3Cl(dppp2)]), we observe the concomitant formation of an 3IL ππ* (IL = intra ligand) excited state. For [Re(CO)3Cl(dppp2)] and [Re(CO)3Cl(dppp3)] in toluene, a mixture of 3MLCT(phen) (phen = phenanthroline) and 3MLCT(phz) states appear to form together, and decay at the same rate. Inclusion of an nitrogen atom in the phz moiety of the dppz ligand lowers the ‘phz’ localised lowest unoccupied molecular orbital (LUMO) energy potentially favouring population of the 3MLCT(phz) state. This effect is more pronounced for [Re(CO)3Cl(dppp3)] with a more positive reduction potential (E½ = −1.16 vs Fc+/Fc in CH2Cl2) compared to [Re(CO)3Cl(dppp2)] (E½ = −1.20 V vs Fc+/Fc in CH2Cl2). For [Re(CO)3Cl(dppp2Br)], lowering of the LUMO energy results in an even more positive potential (E½ = −1.10 vs Fc+/Fc in CH2Cl2) and this can be seen to affect the photophysics. We find the excited state lifetime for each complex increases with decreasing dielectric constant, where their lifetime in toluene is greater than 100 times longer than that observed in d6-DMSO.

Improving methane selectivity of photo-induced CO2 reduction on carbon dots through modification of nitrogen-containing groups and graphitization

The photocatalytic performance of carbon dots is strongly related to surface modifications and graphitization. Herein, we show that carbon dots without metal loaded can serve as an efficient photocatalyst for reducing CO2. The conjugate carbon great π could stabilize the photogenerated electrons, which turned out to improve the separation of the photogenerated electron-hole pairs and can kinetically promote interfacial reaction. Besides, the strong chemisorption of the nitrogen-containing groups on the carbon dots to the CO would help to further conversion of the intermediate in the demonstrated CO2 photo-reduction systems. As a result of these merits, the highly graphitized carbon dots prepared from graphene oxide with plenty of nitrogen-containing groups exhibit 74.8% electronic selectivity of methane. This strategy provides an important requirement for designing of CO2 photocatalysts.

Tailoring performance of La-modified TiO2 nanocatalyst for continuous photocatalytic CO2 reforming of CH4 to fuels in the presence of H2O

Photo-induced CO2 reforming of CH4 in the presence of H2O over La-modified TiO2 nanoparticles in a continuous flow photoreactor has been investigated. The structure and properties of the catalyst samples, synthesized by a sol-gel method, were systematically characterized by XRD, Raman, SEM, TEM, CO2-TPD, TGA, N2-sorption, XPS, UV–Vis DRS and PL spectroscopy. The crystallite size was reduced while, BET surface area and basicity were increased due to the presence of La2O3. The La-modified TiO2 nanocatalysts were tested under different catalyst loading, irradiation time, reaction temperature and type of reductants. The main products detected over La/TiO2 catalysts during photo-induced CO2-CH4 reaction system were CO, H2 and C2H6. The amount of CO produced over 5 wt.% La/TiO2 was 9.6 fold more the amount of CO produced by pure TiO2. When H2O was added to the CO2-CH4 reaction system, the yield of CO increased 37 fold higher over 5 wt.% La/TiO2 compared to TiO2. The enhanced photocatalytic performances can be attributed to the synergistic effect of La2O3 for CO2 adsorption with hindered charge recombination rate by La3+ and appropriate redox potentials. The photocatalytic turnover productivity (PTOP), calculated for the first time, presented amounts of products evolved with the photon energy consumption. The highest PTOP number achieved for CO production using the CO2-CH4-H2O reaction system was 3.83 fold higher than PTOP achieved in CO2-CH4 reaction system. However, PTOP for the production of H2 and C2H6 in CO2-CH4 system was 1.2 and 2.1 fold higher than the CO2-CH4-H2O reaction system, respectively. The stability test revealed prolonged life time of La/TiO2 in cyclic runs for dynamic CO2-CH4 conversion to fuels in the presence of H2O than using only CO2-CH4 reaction system. Therefore, CO2-CH4 could efficiently be converted to fuels over a La/TiO2 catalyst while the addition of H2O could promote both photoactivity and stability.