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Objectives: This study aims to determine the relationship between weight loss and outcomes in patients with atrial fibrillation (AF) ablation, as well as the potential dose-response relationship.Background: Obesity is an independent risk factor for AF, and obesity can affect the prognosis of AF. However, the role of weight loss on outcomes after ablation remains unclear.Methods: The Cochrane Library, PubMed, and Embase databases were searched to identify studies that reported a relationship between weight loss and ablation up to August 17, 2021. Relative risks (RRs) were pooled using random-effects models.Results: One randomized, open-labeled clinical trial and seven cohort studies involving 1150 patients were included. The mean body mass index of all included studies was over 30 kg/m2. The clinical trial showed nonsignificant benefit of weight loss intervention on AF recurrence (odd risk=1.02, 95% confidence interval [CI]: 0.70-1.47). Meta-analysis based on observational studies showed that the recurrence rate of AF after ablation was significantly reduced (RR=0.43, 95% CI: 0.22-0.81, I2 =97%) in relatively obesity patients with weight loss compared with the control group (morbidly obese patients without weight change). Each 10% reduction in weight was associated with a decreased risk of AF recurrence after ablation (RR=0.54, 95% CI: 0.33-0.88) with high statistical heterogeneity (I2 =76%). An inverse linear association (Pnon-linearity =0.27) between AF relapse and increasing weight loss was found.Conclusions: Our results first suggest an inverse dose-response association between weight loss in risk of recurrent AF after ablation in obese patients.

Recent reports of potential harmful effects of nonsteroidal anti-inflammatory drugs (NSAIDs) in treating patients with coronavirus disease 2019 (COVID-19) have raised great concern.We searched the PubMed, EMBASE, Cochrane Library and MedRxiv databases to examine the prevalence of NSAID use and associated COVID-19 risk, outcomes and safety.Twenty-five studies with a total of 101 215 COVID-19 patients were included. Prevalence of NSAID use among COVID-19 patients was 19% (95% confidence interval [CI] 14-23%, no. of studies [n] = 22) and NSAID use prior to admission or diagnosis of COVID-19 was not associated with an increased risk of COVID-19 (adjusted odds ratio [aOR] = 0.93, 95% CI 0.82-1.06, IBased on current evidence, NSAID use prior to admission or diagnosis of COVID-19 was not linked with increased odds or exacerbation of COVID-19. NSAIDs might provide a survival benefit, although they might potentially increase the risk of stroke. Controlled trials are still required to further assess the clinical benefit and safety (e.g., stroke and acute renal failure) of NSAIDs in treating patients with COVID-19.

Phenol is one of the most widespread, toxic and recalcitrant compounds in water sources. Due to its persistent nature, conventional wastewater treatment methods are not effective to remove or degrade phenol from water. In this work, novel photocatalysts were developed to effectively degrade phenol under simulated sunlight. The catalysts were composed of one-dimensional titanium dioxide (TiO2) nanorods decorated with silver (Ag) nanoparticles, coated by an ultrathin magnesium oxide (MgO) overlayer through atomic layer deposition (ALD). Material properties of prepared catalysts were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV-vis diffuse reflectance spectroscopy (UV-Vis DRS). The photocatalytic performance of phenol degradation under simulated sunlight was evaluated and correlated with the material properties. The Ag nanoparticles promoted light absorption and transfer of photo-induced electron-hole pairs from within TiO2 nanorods to the catalyst surface. The ultrathin MgO overlayer with a sub-nanometer thickness did not hinder charge transfer to the surface, but rather, it further increased the light absorption and inhibited surface charge recombination through a surface passivation effect, promoting phenol degradation. The photocatalytic reaction mechanism was investigated by examining hydroxyl and superoxide radical production in the photocatalytic system. The results from this work demonstrated a new strategy for fabricating efficient solar-driven photocatalysts for the degradation of persistent water contaminants.

In this work, we have prepared porous TiO2 with mixed anatase-rutile phases from a metal-organic framework MIL-125 and employed atomic layer deposition (ALD) method to coat an ultrathin MgO overlayer on porous-TiO2. The CO2 photoreduction performance of porous-TiO2 was more than 4 times higher than that of commercial Degussa P25. The MgO coating on porous-TiO2 by ALD in the range of 1 to 100 atomic layers all improved CO2 photoreduction performance, with 5 layers of MgO being the optimal, delivering 4 times higher CO production than that by pristine porous-TiO2 and 21 times higher than P25. It is demonstrated that the uniform dispersion of MgO on TiO2 surface led to increased concentration of surface Ti3+ species and Mg bonded hydroxyl groups, which are active sites for CO2 adsorption and photoreduction. The ALD layer also served to passivate the TiO2 surface states and hinder surface electron-hole recombination. In addition, a conventional wet-impregnation (WI) method was applied to incorporate MgO on porous-TiO2 to serve as a comparison. The WI modified MgO/TiO2 samples were more active than pristine porous-TiO2 but less active than ALD modified MgO/TiO2, because the ALD samples presented significantly higher amounts of surface Ti3+ than WI samples due to higher and more uniform MgO surface coverage by ALD coating. Findings from this original work on ALD modification to enhance photocatalytic performance may be extended to other photocatalyst systems and other catalytic reactions.

IntroductionRecent reports of potential harmful effects of nonsteroidal anti-inflammatory drugs (NSAIDs) in patients with Corona Virus Disease 2019 (COVID-19) have provoked great concern. Therefore, the safety of NSAIDs is still questioned.MethodsWe searched the PubMed, EMBASE, Cochrane Library and Web of Science databases from December 2019 to January 2021 to examine use prevalence for NSAIDs in general, as well as associated COVID-19 risk and outcomes. This study has been registered with PROSPERO (CRD42019132063)ResultsWe included 25 studies with a total of 101,215 COVID-19 patients. The use of NSAIDs in COVID-19 patients reached 19%. Exposure to NSAIDs was not associated with significantly increased risk of developing COVID-19 (odds ratio [OR]=0.98, 95% confidence interval [CI]: 0.78-1.24; I2=82%), hospitalization (OR=1.06, 95%CI: 0.76-1.48; I2=81%), mechanical ventilation (OR=0.71, 95%CI: 0.47-1.06; I2=38%), and length of hospital stay. Moreover, use of NSAIDs was significantly associated with better outcomes, including severity of COVID-19 (OR=0.79, 95%CI: 71-0.89; I2=0%) and death (OR=0.68, 95%CI: 0.52-0.89; I2=85%) in patients with COVID-19. Regarding safety outcomes, exposure to NSAIDs was associated with increased risk of stroke (OR=2.32, 95%CI: 1.04-5.2; I2=0%), but not with myocardial infraction (OR=1.49; p=0.66; I2=0%), overt thrombosis (OR=0.76, p=0.50; I2=28%) and major bleeding (p=0.61).ConclusionBased on current evidence, exposure to NSAIDs is not linked to increased odds or exacerbation of COVID-19 in the general COVID-19 population. Furthermore, administration of NSAIDs might have better outcomes and survival benefits in the general COVID-19 population, although potentially increasing the risk of stroke. Use of NSAIDs might be safe and beneficial in COVID-19. Future observational and randomized control trials are needed for further confirmation.

A well-designed nanocomposite structure, Au/Al2O3/TiO2, that is Au-decorated TiO2 with an atomic-layer-deposited Al2O3 interlayer between Au and TiO2, was synthesized to study the role of plasmonic Au nanoparticles on photocatalytic CO2 reduction as well as the influence of the interlayer. Localized surface plasmon resonance induced hot electron injection and near-field enhancement, together with the enhanced charge separation caused by the Au NPs were found responsible for the promoted photocatalytic CO2 reduction on Au-modified TiO2. The Al2O3 interlayer inhibited electron transfer and dampened the near-field enhancement effect; however, it also served as passivation layer to suppress electron–hole recombination on the TiO2 surface. To further identify the significance of each of the mechanisms, photocatalysts with tailored thickness of Al2O3 interlayer and varied size of Au NPs were carefully synthesized, characterized, and tested for CO2 photoreduction with water. A finite difference time domain simul...

The development of high-performance electrocatalysts for CO2 reduction reaction (CO2RR) is a prerequisite to enable CO2-to-fuels electrolysis a feasible solution for reaching a carbon neutral cycle and producing value-added fuels. In this work, we report the design of a novel nanostructured electrocatalyst consisting of carbon nanotube/carbon nanosheet architecture with N and Fe doping (NFe-CNT/CNS) by a SiO2-protected calcination strategy. The hierarchical structure of CNT/CNS affords abundant N-induced defects and Fe−N species as highly active sites and facilitates mass transportation, and carbon nanotube also offers a smooth route for charge transfer in the CO2RR process. These synergistic merits afford NFe-CNT/CNS with high performance for CO2RR in terms of a maximum FE of 69% at a low overpotential of 0.48 V, a small Tafel slope of 89 mV dec−1, and enhanced stability for CO production in aqueous solution. The findings demonstrate that the integration of structural design and dopants optimization is effective to boost electrocatalytic activity of nanocarbons for CO2 reduction.

We report a new approach of photo-thermo-chemical CO2(dry) reforming of methane (PTC-DRM) to produce syngas using concentrated sunlight as the energy input. A unique catalyst, Pt supported Si-modified CeO2, was designed for this novel PTC-DRM reaction by integrating photocatalytic and thermocatalytic effects, where Pt was the thermocatalytic DRM catalyst and co-catalyst for photocatalysis, CeO2 was the DRM support and semiconductor photocatalyst, and Si was the promoter and stabilizer. Under 30 equivalent suns irradiation at 600 °C in 30 h, the production rates of H2 and CO reached a stable level at 90 and 154 mmol g−1 h−1, respectively, which were 5 and 2 times higher than those obtained in the dark at the same temperature. The significantly enhanced catalytic performance and stability under solar irradiation, taking advantages of the synergy of photocatalytic and thermocatalytic effects, demonstrates the feasibility of a new direction in low-carbon fuel production from sunlight.

Objective Controversial results of the association between green tea consumption and risk for esophageal cancer (EC) were reported by previous meta-analysis. Thus, the aim of this study was to quantitatively investigate the association. Methods The Cochrane Library, PubMed, and EMBASE databases were searched for relevant studies. We used a “one-stage approach” with a restricted cubic spline model to summarize the dose-specific relationships between green tea and risk for EC. Odds ratios (ORs) were used to measure the effects. Fourteen studies were included with a total of 5057 ECs among 493 332 participants. Results In the dose–response analysis, the summary OR for a 1 cup/d increase in green tea was 1.00 (95% confidence interval [CI], 0.95–1.04; I2 = 77%). No nonlinearity association was observed between tea consumption and risk for EC (P = 0.71 for nonlinearity). In the subgroup of sex, the summary OR for a 1 cup/d increase in green tea was 1.03 (95% CI, 0.95–1.11, I2 = 67%) for men and 0.79 (95% CI, 0.68–0.91; I2 = 0%) for women. Conclusion Contrary to previous studies, based on current evidence, the present dose–response study suggested no association between green tea and risk for EC. However, there might be a protective effect of green tea in women. Notably, our conclusion might be influenced by limited studies and potential bias, such as dose of green tea assessment and select bias of case–control studies. Further larger number, prospective, and well-designed larger-scale studies are needed to provide more precise evidence, especially in women and more regions (United States and Europe).

Highly stable and active TiO2-coated Ag-modified ZnO nanorods supported on stainless steel mesh (xTi@Ag_ZnO-SS) were successfully synthesized in this work. A low-temperature one-pot hydrothermal method was used to grow Ag_ZnO on stainless steel mesh, and subsequently, an atomic layer deposition (ALD) technique was applied to deposit a TiO2 layer on the surface of Ag_ZnO-SS. The addition of Ag-enhanced photoactivity via favored charge carrier transfer and the TiO2 layer improved stability through suppressed corrosion under UV irradiation, which was demonstrated by cycling performance for RhB photodegradation in two aspects: morphology and photoactivity. After 10 cycles (2 h/cycle) RhB degradation tests under UV irradiation, all the TiO2-protected ZnO materials maintained more intact nanorods structure and more than 80% of the initial photoactivity in the 1st cycle, whereas the ZnO materials without TiO2 coating were drastically deconstructed and only had 56% of initial photodegradation ability. Comprehensive study indicated that thicker TiO2 layers resulted in higher stability but lower photoactivity due to the inhibited charge transfer. The developed TiO2@Ag_ZnO nanorods immobilized on stainless steel mesh demonstrated a promising strategy for the design of highly stable and active photocatalysts endowed with great industrial scalability and practicality.

Solar-driven heterogeneous photocatalysis has been widely studied as a promising technique for degradation of organic pollutants in wastewater. Herein, we have developed a sulfite-enhanced visible-light-driven photodegradation process using BiOBr/methyl orange (MO) as the model photocatalyst/pollutant system. We found that the degradation rate of MO was greatly enhanced by sulfite, and the enhancement increased with the concentration of sulfite. The degradation rate constant was improved by 29 times in the presence of 20 mM sulfite. Studies using hole scavengers suggest that sulfite radicals generated by the reactions of sulfite (sulfite anions or bisulfite anions) with holes or hydroxyl radicals are the active species for MO photodegradation using BiOBr under visible light. In addition to the BiOBr/MO system, the sulfite-assisted photocatalysis approach has been successfully demonstrated in BiOBr/rhodamine B (RhB), BiOBr/phenol, BiOI/MO, and Bi2O3/MO systems under visible light irradiation, as well as in...

Novel FeOOH and Fe 2 O 3 co-grafted TiO 2 photocatalysts were synthesized and tested for bisphenol A (BPA) degradation in water under simulated solar and visible light irradiations. The grafting temperature was simply controlled to adjust the FeOOH and Fe 2 O 3 compositions, with 55 °C being the optimal temperature that led to the highest BPA degradation. Co-grafted FeOOH and Fe 2 O 3 on TiO 2 is advantageous over mono-grafted or un-grafted TiO 2 , because FeOOH promotes BPA adsorption and Fe 2 O 3 enhances photocatalytic activity by facilitating the interfacial charge transfer. Findings from this study contribute to the fabrication of efficient, low-cost photocatalysts for water pollutant removal.

In this work, anatase nanorods (ANR) of TiO2 with active facet {100} as the major facet were successfully synthesized, and reducing the ANR by NaBH4 led to the formation of gray colored oxygen deficient TiO2-x (ReANR). On the surface of ReANR, a thin layer of Al2O3 was deposited using atomic layer deposition (ALD), and the thickness of Al2O3 varied by the number of ALD cycles (1, 2, 5, 10, 50, 100, or 200). The growth rate of Al2O3 was determined to be 0.25 A per cycle based on high-resolution TEM analysis, and the XRD result showed the amorphous structure of Al2O3. All the synthesized photocatalysts (ANR, ReANR, and Al2O3 coated ReANR) were tested for CO2 photocatalytic reduction in the presence of water vapor, with CO detected as the major reduction product and CH4 as the minor product. Compared with ANR, ReANR had more than 50% higher CO production and more than ten times higher CH4 production due to the oxygen vacancies that possibly enhanced CO2 adsorption and activation. By applying less than 5 cycles of ALD, the Al2O3 coated ReANR had enhanced overall production of CO and CH4 than uncoated ReANR, with 2 cycles being the optimum, about 40% higher overall production than ReANR. Whereas, both CO and CH4 production decreased with increasing number of ALD cycles when more than 5 cycles were applied. Photoluminescence (PL) analysis showed an ultrathin layer of Al2O3 (2 cycles of ALD) coating on the ReANR was able to reduce the charge carrier recombination rate, likely because of the passivation of surface states. On the other hand, a relatively thick layer of Al2O3 may act as an insulation layer to prohibit electron migration to the catalyst surface. This work gives valuable insights on the application of ALD coating on photocatalysts to promote CO2 photoreduction to fuels.

Membrane fouling caused by natural organic matters such as humic acid has been one of the major obstacles inhibiting the wide application of membrane technologies for water treatment. In this work, a novel membrane made of interconnecting TiO 2 nanowires, Fe 2 O 3 nanoparticles, and graphene oxide (GO) sheets was prepared via a simple hydrothermal, colloidal blending, and vacuum filtration method. Membrane performance of humic acid removal under simulated solar irradiation and in the dark were compared for membranes with different Fe 2 O 3 /TiO 2 /GO compositions. It was demonstrated that enhanced humic acid removal was achieved due to the greater adsorption of humic acid by Fe 2 O 3 nanoparticles and the improved photocatalytic activity of TiO 2 by the GO sheets that can facilitate separation of photo-induced electron-hole. An optimal Fe 2 O 3 :TiO 2 :GO weight ratio of 50:100:10 was identified, and over 98% humic acid removal was achieved in a short-term test (2 h) and 92% removal in a 12 h test under solar irradiation. By contrast, only 51% humic acid removal was obtained by the same membrane in dark in the 12 h test. A lower pressure drop across the membrane was also observed under solar irradiation (20 kPa) compared with that in the dark (50 kPa). This nanomaterial-based novel membrane contributes to the development of a more effective water treatment technology.

Photocatalytic reduction of CO 2 into value-added fuels (e.g., CO and CH 4 ) is a promising approach of storing solar energy and mitigating greenhouse gas emissions simultaneously. In this work, a novel material of crystallized titanium-embedded magnesium-aluminum layered double hydroxides (MgAlTi-LDHs) is developed and tested for CO 2 photoreduction with water. Three different materials synthesis methods were explored: (1) coprecipitation, (2) coprecipitation + hydrothermal, and (3) coprecipitation + calcination + reconstruction. The coprecipitation method alone only produced amorphous TiO x species in the LDHs, while the latter two methods resulted in the formation of crystalline anatase TiO 2 when appropriate treatment temperatures were applied but the specific surface area was decreased due to the thermal treatment. Compared with commercial TiO 2 -P25 nanoparticles, all MgAlTi-LDHs prepared in this work demonstrated two to four times higher catalytic activities in CO 2 photoreduction to CO. Among the MgAlTi-LDHs, the CO 2 photoreduction activity was affected by both the crystallinity of TiO 2 and the specific surface area. Consequently, the material hydrothermally treated at 150–200 °C demonstrated the highest CO production due to a well-balanced TiO 2 crystallinity and specific surface area. Findings in this work contribute to the development of efficient photocatalysts for CO 2 reduction and advance the understanding of the catalyst property-activity relationships.

This work for the first time reports engineered oxygen-deficient, blue TiO2 nanocrystals with coexposed {101}-{001} facets (TiO2–x{001}-{101}) to enhance CO2 photoreduction under visible light. The TiO2–x{001}-{101} material demonstrated a relatively high quantum yield (0.31% under UV–vis light and 0.134% under visible light) for CO2 reduction to CO by water vapor and more than 4 times higher visible light activity in comparison with TiO2 with a single {001} plane or {101} plane and TiO2(P25). Possible reasons are the exposure of more active sites (e.g., undercoordinated Ti atoms and oxygen vacancies), the facilitated electron transfer between {001} and {101} planes, and the formation of a new energy state (Ti3+) within the TiO2 band gap to extend the visible light response. An in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) study was applied to understand the roles of coexposed {001}-{101} facets and Ti3+ sites in activating surface intermediates. The in situ DRIFTS analysis ...

Background The relationship between serum hemoglobin A1c (HbA1c) and atrial fibrillation (AF) or postoperative AF (POAF) in coronary artery bypass (CABG) patients is still under debate. It is also unclear whether there is a dose-response relationship between circulating HbA1c and the risk of AF or POAF. Methods and results The Cochrane Library, PubMed, and EMBASE databases were searched. A robust-error meta-regression method was used to summarize the shape of the dose-response relationship. The RR and 95%CI were using a random-effects model. In total, 14 studies were included, totaling 17,914 AF cases among 352,325 participants. The summary RR per 1% increase in HbA1c was 1.16 (95% CI: 1.07–1.27). In the subgroup analysis, the summary RR was 1.13 (95% CI: 1.08–1.19) or 1.12 (95% CI: 1.05–1.20) for patients with diabetes or without known diabetes, respectively. The nonlinear analysis showed a nonlinear (Pnonlinear = 0.04) relationship between HbA1c and AF, with a significantly increased risk of AF if HbA1c was over 6.3%. However, HbA1c (per 1% increase) was not associated with POAF in patients with diabetes (RR: 1.13, P = 0.34) or without known diabetes (RR: 0.91, P = 0.37) among patients undergoing CABG. Conclusion Our results suggest that higher HbA1c was associated with an increased risk of AF, both in diabetes and in without diabetes or with unknown diabetes. However, no association was found between HbA1c and POAF in patients undergoing CABG. Further prospective studies with larger population sizes are needed to explore the association between serum HbA1c level and the risk of POAF.

Phenol is one of the most widespread, toxic and recalcitrant compounds in water sources. Due to its persistent nature, conventional wastewater treatment methods are not effective to remove or degrade phenol from water. In this work, novel photocatalysts were developed to effectively degrade phenol under simulated sunlight. The catalysts were composed of one-dimensional titanium dioxide (TiO

Carbon decorated on commercial TiO2 nanoparticles (P25 and P90) with optimized carbon concentration and structure were fabricated by a facile process employing carbonization method. In addition, the raw materials for Carbon-TiO2 (C-TiO2) preparation are commercially available and relatively cheap and the preparation method is simple and easy to be scaled up, making the reported process a promising method for mass production of electrode materials for high performance lithium-ion batteries (LIBs). The materials were applied as LIBs anodes and the electrochemical results showed that 1.9 wt% C decorated P90 (1.9%C-P90) possessed a very high initial discharge capacity of 231 mA h g−1 and the capacity was retained at 173 mA h g−1 after 100 cycles at a current density of 30 mA g−1. Even at a high current density of 300 mA g−1 it delivered a very stable reversible capacity of 130 mA h g−1. The electrochemical performance of C-P90 was superior to C-P25 because of its higher specific surface area and larger anatase fraction that can accommodate more lithium ions. 1.9% carbon was found to form an optimized carbon layer on TiO2 that can improve the electronic conductivity. The simple method and cheap materials for electrode material preparation have great potential for commercialization.

A series of magnesium/aluminum (MgAl) layered double oxide (LDO) grafted TiO2 cuboids (MgAl-LDO/TiO2) with various molar ratios of (Mg + Al) to Ti were synthesized by a combination of hydrothermal and coprecipitation methods, in which the growth of MgAl-LDO platelets was controlled. The MgAl-LDO/TiO2 composite materials were used for photocatalytic CO2 reduction with water vapor under UV light irradiation in a continuous-flow reactor. CO was found to be the main product from CO2. At near room temperature (e.g., 50 °C), MgAl-LDO/TiO2 did not significantly enhance CO2 reduction compared with pure TiO2 cuboids. At a moderately elevated reaction temperature (e.g., 150 °C), the MgAl-LDO/TiO2 sample with an optimum 10 wt.% MgAl-LDO loading demonstrated CO2 reduction activity five times higher than that of bare TiO2 cuboids. The photo-induced electrons on TiO2 may migrate to the MgAl-LDO/TiO2 interfacial sites to promote CO2 reduction. Findings in this work may lead to a new area of hybrid adsorbent/photocatalyst materials that are capable of sequential CO2 capture and photocatalytic conversion.

In this paper we report a novel architecture of hierarchical 3D porous carbon microspheres (PCM) to encapsulate ZnO-CoO nanoparticles that serves as an advanced anode for high-performance lithium-ion battery (LIB). The PCM is fabricated by a facile aerosol spray pyrolysis method, and ZnO-CoO composite nanoparticles are infiltrated into the PCM by a simple one-pot hydrothermal procedure (i.e., ZnO-CoO@PCM). The developed hybrid material provides several advantages: (1) partial replacement of CoO with ZnO to offer a low-cost and eco-friendly candidate anode, (2) a continuous and large surface area (1236 m 2 g −1 ) carbon network for improved electrical conductivity and uniform dispersion of ZnO-CoO nanoparticles, and (3) porous structure for good electrolyte diffusion and fast Li-ion transport and to buffer the large volume expansion of the metal oxides. As a result, this new ZnO-CoO@PCM nanocomposite demonstrates a higher reversible capacity (1250 mAh g −1 after 150 cycles at a current density of 100 mA g −1 ), more excellent cycling stability, and better rate capability than a ZnO-CoO/PCM mixture and than a non-porous ZnO-CoO/carbon black mixture. The 3D porous nanocomposite architecture in this work could shed light on the design and synthesis of other metal oxides electrodes for energy storage.

Photocatalytic reduction of CO2 with H2O vapor for CO production at a temperature of 150 °C was studied using porous MgO–TiO2 microspheres as the photocatalysts with the benefits of improved CO2 adsorption by incorporating MgO and enhanced products/intermediates desorption at a higher temperature. The MgO–TiO2 microspheres were fabricated by two methods: (1) a one-step spray pyrolysis method using TiO2 (P25) nanoparticles dispersed in Mg(NO3)2 solution as the precursors (Mg/Ti-SP), and (2) spray pyrolysis synthesis of pure TiO2 (P25) microspheres first and then wet-impregnation with MgO (Mg/Ti-WI). The two material synthesis methods led to different MgO dispersion on the TiO2 surface. For Mg/Ti-SP, the strong aggregation of MgO nanoparticles caused a rough surface of the MgO–TiO2 microsphere; while for Mg/Ti-WI, MgO was more uniformly deposited leading to a much smoother surface of the microsphere. The surface dispersion of MgO was found to significantly affect the performance of MgO–TiO2 in CO2 photoreduction. At the same MgO concentration, Mg/Ti-SP had more than two times higher activity than Mg/Ti-WI, and most importantly, little deactivation of the catalyst was observed on Mg/Ti-SP while Mg/Ti-WI started to deactivate after 1 to 2 h when the reactor was operating in a continuous flow mode. The ease of photo-induced electron transfer to the catalyst surface may have contributed to the superb activity of Mg/Ti-SP samples. The optimum MgO concentration was found to be 5% for both types of materials. Besides the dispersion of MgO, we also found that the CO2 adsorption–desorption dynamics strongly influenced the CO2 photoreduction. The results from in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) revealed two advantages of Mg/Ti-SP over Mg/Ti-WI: (1) more abundant bicarbonates (important intermediates for CO production) on the surface and (2) easier desorption/transformation of intermediates.

Ag nanoparticles deposited on porous TiO2 microspheres with controllable Ag valence and TiO2 crystal phase were prepared through a sequential hydrothermal, ultrasonic spray pyrolysis and in situ photoreduction process. The crystal phase of TiO2, i.e., pure anatase (A), an anatase-rich anatase/brookite mixture (AB), or a brookite-rich anatase/brookite mixture (BA), was controlled by varying the hydrothermal reaction environment. The as-prepared Ag/TiO2 was dominated by the Ag(I) species, while Ag(0) was the major Ag species upon in situ photoreduction of the as-prepared Ag(I)/TiO2. The Ag/TiO2 composites were applied as photocatalysts for CO2 reduction with H2O, using methanol as a hole scavenger under UV–vis irradiation. Simultaneous production of hydrogen (H2) and carbon-containing fuels (CO, CH4) was observed. The CH4 and H2 production rates by Ag(0)/TiO2 exhibited a two-fold enhancement compared with Ag(I)/TiO2. The Ag(0)/TiO2 catalysts using TiO2(AB) as the support demonstrated 50% higher activity than using TiO2(A) as the support and more than three times higher activity than using TiO2(BA) and TiO2(P25) as the supports. In addition, the novel in situ photoreduction method of producing Ag(0) nanoparticles was superior to conventional ex situ photo-deposition and wet-impregnation methods, as evidenced by one order of magnitude higher activity of the catalysts prepared by the novel method. The superb activity of the Ag(0)/Ti(AB) catalysts was ascribed to their large surface area, small and well-dispersed Ag(0) nanoparticles, and an enhanced interfacial charge transfer between the anatase and brookite nanocrystals.

The incorporation of Cu species in TiO2 photocatalysts is critical in photocatalytic CO2 reduction to fuels, but the effect of Cu valence is poorly understood. In this work, Cu/TiO2 (P25) nanoparticle catalysts were prepared by a simple precipitation and calcination method. The as-prepared Cu/TiO2 sample was dominated by Cu2+ species. Thermal pretreatment of the as-prepared samples in He and H2 atmosphere resulted in the transition to a surface dominated by Cu+ and mixed Cu+/Cu0, respectively, confirmed by in situ X-ray photoelectron spectroscopy (XPS) and diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS) analyses. These thermal pretreatments in reducing atmospheres also induced the formation of defect sites such as oxygen vacancies and Ti3+. The various Cu/TiO2 catalysts were tested in CO2 photoreduction with water vapor under simulated solar irradiation, and their activities were in the order of as-prepared (unpretreated)

CO2 photoreduction with water vapor has been studied on three TiO2 nanocrystal polymorphs (anatase, rutile, and brookite) that were engineered with defect-free and oxygen-deficient surfaces, respectively. It was demonstrated that helium pretreatment of the as-prepared TiO2 at a moderate temperature resulted in the creation of surface oxygen vacancies (VO) and Ti3+ sites on anatase and brookite but not on rutile. The production of CO and CH4 from CO2 photoreduction was remarkably enhanced on defective anatase and brookite TiO2 (up to 10-fold enhancement) as compared to the defect-free surfaces. Defective brookite was photocatalytically more active than anatase and rutile, probably because of a lower formation energy of VO on brookite. The results from in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analyses suggested that (1) defect-free TiO2 was not active for CO2 photoreduction since no CO2– is generated, and (2) CO2 photoreduction to CO possibly underwent different reaction ...

Simultaneous photocatalytic hydrogen production and CO 2 reduction (to form CO and CH 4 ) from water using methanol as a hole scavenger were investigated using silver-modified TiO 2 (Ag/TiO 2 ) nanocomposite catalysts. A simple ultrasonic spray pyrolysis (SP) method was used to prepare mesoporous Ag/TiO 2 composite particles using TiO 2 (P25) and AgNO 3 as the precursors. The material properties and photocatalytic activities were compared with those prepared by a conventional wet-impregnation (WI) method. It was found that the samples prepared by the SP method had a larger specific surface area and a better dispersion of Ag nanoparticles on TiO 2 than those prepared by the WI method, and as a result, the SP samples showed much higher photocatalytic activities toward H 2 production and CO 2 reduction. The optimal Ag concentration on TiO 2 was found to be 2 wt%. The H 2 production rate of the 2% Ag/TiO 2 –SP sample exhibited a six-fold enhancement compared with the 2% Ag/TiO 2 –WI sample and a sixty-fold enhancement compared with bare TiO 2 . The molar ratio of H 2 and CO in the final products can be tuned in the range from 2 to 10 by varying the reaction gas composition, suggesting a viable way of producing syngas (a mixture of H 2 and CO) from CO 2 and water using the prepared Ag/TiO 2 catalysts with energy input from the sun.

Anatase TiO2 nanorods (ANR) with active facet {100} as the dominating facet were synthesized and oxygen deficient TiO2-X nanorods (ReANR) was prepared by reducing TiO2 using NaBH4. A thin layer of Al2O3 was coated on the surface of ReANR by atomic layer deposition (ALD), and the thickness of Al2O3 was tailored by varying the cycle number (1, 2, 5, 10, 50, 100, or 200) of ALD operation. The growth rate of Al2O3 was 0.25 Å per cycle as evidenced by high-resolution transmission electron microscopy, and the amorphous structure of Al2O3 was determined based on X-ray diffraction results. ANR, ReANR and Al2O3 coated ReANR were tested for CO2 photoreduction with water, with CO and CH4 as the major and minor products, respectively. Compared with ANR, ReANR had more than 50% higher CO production and more than ten times higher CH4 production due to the oxygen vacancies that possibly promoted CO2 adsorption and activation. With less than 5 cycles of ALD, Al2O3 coated ReANR had enhanced overall production of CO and CH4 than uncoated ReANR, with 2 cycles being the optimum, about 40% higher overall production than ReANR. Whereas, when more than 5 cycles were applied, both CO and CH4 production decreased with increasing number of ALD cycles. Photoluminescence (PL) analysis showed the both 2 cycles and 200 cycles of Al2O3 ALD coating layer on the ReANR were able to reduce the charge carrier recombination rate, likely because of the passivation of surface states. However, a relatively thick layer of Al2O3 may act as an insulation layer to prohibit electron migration to the catalyst surface. This work gives valuable insights on the application of ALD coating on photocatalysts to promote CO2 photoreduction to fuels.

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A novel MgO-patched TiO2 microsphere photocatalyst demonstrated 10 times higher activity toward CO production from CO2 photoreduction with H2O vapor, when the reaction temperature increased from 50 to 150 °C. The catalytic performance of hybrid MgO-TiO2 was much more stable than TiO2, particularly at a higher temperature, likely due to easier desorption of reaction intermediates and the enhanced CO2 adsorption by MgO.

Among the three naturally existing phases of TiO2, brookite is the least studied as a photocatalyst. In this study, single-phase anatase and brookite, and mixed-phase anatase–brookite TiO2 nanomaterials were synthesized through a hydrothermal method. The anatase–brookite phase content was controlled by adjusting the concentration of urea in the precursor solution. XRD, Raman spectroscopy, and high-resolution TEM were used to confirm the crystal structures. SEM and TEM analyses demonstrated that anatase TiO2 were nearly spherical nanoparticles while brookite TiO2 were rod-shaped nanoparticles. UV-vis diffuse reflectance spectroscopy showed a blue shift in absorption spectra with increasing brookite content. The photocatalytic activities of the prepared bicrystalline TiO2 were evaluated for CO2 photoreduction in the presence of water vapor for production of solar fuels (CO and CH4). The activities were compared with those of pure anatase, pure brookite, and a commercial anatase–rutile TiO2 (P25). The results showed that bicrystalline anatase–brookite was generally more active than single-phase anatase, brookite, and P25. The bicrystalline mixture with a composition of 75% anatase and 25% brookite showed the highest photocatalytic activity, likely due to the enhanced interfacial charge transfer between anatase and brookite nanocrystals. In situ DRIFTS analysis showed that CO2− and HCO3− species were active reaction intermediates for CO2 photoreduction while the accumulation of non-reactive CO32− species on the TiO2 surface may be detrimental.