Perovskite LaCoO3 was successfully synthesized using natural sugarcane bagasse with tunable oxygen vacancy. The preparation process was studied to elucidate the interaction between sugarcane bagasse and metal ions. And the prepared catalysts were characterized by XRD, SEM, XPS, DRS, and PL. The results indicated that bagasse was partly hydrolyzed by metal nitrate solution, and the gel was formed by adsorption and complexation between rich organic groups and metal ions, differing from citric acid complexation with metal ions. The bagasse fragments mediation in the process could modulate the amount of oxygen vacancy. An appropriate oxygen vacancy may act as the defect energy level above the valence band of LaCoO3 to adjust the band gap and accelerate charge transfer, resulting in high photocatalytic performance. Photocatalytic tests in formaldehyde aqueous solution under visible light demonstrated that LaCoO3 prepared by sugarcane bagasse exhibited higher hydrogen production than that prepared by conventional citric acid method.Keywords: Hydrolysis; Oxygen vacancy; Perovskite; Photocatalysis; Sugarcane bagasse;

•TiO2 precursor with Au and La by heat treatment in H2/CO2 has been proposed to prepare highly photocatalytic Au-La2O3/TiO2.•Small-sized particles induce a synergistic interaction of La and Au to extend the absorption edge to visible light region.•La2O2CO3 on the catalyst surface facilitates the basicity optimization and contributes to the CH bond cleavage in HCOO-.•ALT-H2/CO2 can produce an optimal H2 generation rate of 178.4 μmol gcat−1 h-1.A simple modified sol-gel method by calcinating titanium dioxide precursor with gold and lanthanum in heat treatment under H2/CO2 atmosphere has been proposed to prepare highly photocatalytic Au-La2O3/TiO2 (ALT) hybrid. Characterization results show that gold nanoparticles with small particle size are embedded in a nearly homogeneous component, which may induce a strong interaction of La and Au co-doping to obtain an appropriately modified bandgap structure and extend the absorption edge to visible light region. The formation of La2O2CO3 on the surface could facilitate to the basicity optimization of the photocatalyst and contribute to the CH bond cleavage in HCOO- to release H2 and CO2 from formic acid (FA). The large surface area and small-sized mesopores structure could provide more active sites for the adsorption of reactant molecules and improve the photocatalytic activity. Benefiting from these positive effects, the ALT photocatalyst calcinating in H2/CO2 demonstrated a great potential in FA photocatalytic decomposition under simulated sunlight irradiation and produced an optimal H2 generation rate of 178.4 μmol gcat−1 h−1 (14.9 mmol gAu−1 h−1), which was approximately 1.3, 1.9 and 2.6 times higher than the same catalysts calcinating in H2, CO2, and N2, respectively.Download high-res image (139KB)Download full-size image

•Availability of aluminum-air battery for microalgae recovery.•Producing energy during microalgae harvesting.•Possible mechanisms of discharging electro-flocculation were discussed.In this study, an efficient electro-flocculation process for Dunaliella salina with energy production by aluminum-air battery has been successfully applied. The formed aluminum hydroxide hydrates during discharging of battery were positively charged, which have a great potential for microalgae flocculation. The precipitation of aluminum hydroxide hydrates by algae also could improve the performance of aluminum-air battery. The harvesting efficiency could reach 97% in 20 mins with energy production of 0.11 kWh/kg. This discharging electro-flocculation (DEF) technology provides a new energy producing process to effectively harvest microalgae.

•Spirulina extract fragments anchor on the surface of TiO2 by thermal treatment.•Spirulina-derived residual groups help anchor dye to enhance light adsorption.•TiO2 films are decorated with spirulina for improving photocurrent.Spirulina-derived residual groups as a special additive to modify the dyed-TiO2/electrolyte interface are introduced to enhance the photovoltaic performance. The interaction between the spirulina residual groups and surface of TiO2 films is investigated. It is found that spirulina extracts molecule split into several small fragments as TiOCH2OH anchoring on the surface of TiO2 by thermal treatment. Spirulina residual groups modified TiO2 photoanodes have a higher light-harvesting capacity and efficient electron transport. As a result, both the Voc and Jsc are improved by TiO2 photoanodes decorated with spirulina derived residual groups, with the short-circuit current of 10.17 mA cm−2 corresponding to the photoelectric conversion efficiency of 4.26%, which is 33.1% higher than the blank DSSC.

•Rapid preparation of PdO/LaCoO3 heterojunction photocatalyst.•Absolute investigation of PdO/LaCoO3 photocatalyst for H2 production from formaldehyde.•An enhanced visible light photocatalytic activity by heterojunction.PdO/LaCoO3 heterojunction photocatalyst was prepared by sol gel process and deposition precipitation method under mild condition, used for H2 production from formaldehyde aqueous solution without any additives at low temperature. We demonstrate through PdO doping that creation of heterojunction on LaCoO3 particles surface can effectively adjust band-gap and Fermi energy levels to apply in hydrogen production from formaldehyde solution under visible light. The work indicate that the heterojunction structure can greatly enhance the charge generation, largely improve the visible light absorptive quality and effectively restrain the recombination of photogenerated electron–holes pairs to exhibit a higher photocatalytic activity. The optimal photocatalytic activity of PdO/LaCoO3 in H2 production from formaldehyde solution under visible light was ten times of LaCoO3 (1.26 mmol h−1 g−1). The photocatalysts composition and optical properties were characterized by XRD, TEM, EDS, XPS, TPR-H2, UV–vis (DRS) and Photoluminescence (PL).

•Biomass–Au–SrTiO3 catalyst for H2 generation from formaldehyde is investigated.•Syzygium–Au–SrTiO3 exhibits much higher activity than glucose–Au–SrTiO3.•Au(I)/Au nanoparticles loaded SrTiO3 was prepared by syzygium extract.•The introduction of syzygium extract helps to enhance the catalytic activity.A novel biomass-synthesized Au–SrTiO3 composite was prepared by syzygium extract and used for H2 evolution from formaldehyde aqueous solution without any additives at low temperature. The as-prepared catalyst exhibits the best performance for H2 evolution (111.15 μmol g−1) compared with the glucose–Au–SrTiO3 and UV–Au–SrTiO3. Through X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectra (FTIR), and X-ray photoelectron spectroscopy (XPS), it was found that the high activity of the syzygium–Au–SrTiO3 catalyst could be linked to the interaction between hydroxyls from biomass and the Au–SrTiO3 which resulted in the Au(I)/Au species. Also, the oxygen vacancies and organic biomass groups on the support may play an important role in the activation of formaldehyde, which was further transformed into formate intermediates and decomposed into hydrogen and carbon dioxide.

The selective decomposition of microcrystalline cellulose (MCC) by Fe-resin (a modified Dowex 50 by cation-exchange) solid catalyst in 5 wt % NaCl solution under hydrothermal conditions has been investigated. The conversion of MCC increases from 24.4% (without catalyst) to 90.9%, and the yield of glucose and levulinic acid (LA) increases from 0.6% and 1.1% (without catalyst) to 38.7% and 33.3%, respectively, under 200 °C for 5 h. The role that Fe-resin/NaCl played in the system is discussed in detail: NaCl could disrupt the hydrogen-bond matrix among cellulose fibers to change highly crystalline cellulose into an amorphous form; Lewis acids on the Fe-resin further boost the depolymerization of amorphous cellulose into water-soluble sugars (WSSs); Fe ions on Fe-resin progressively released into NaCl solution are beneficial to the conversion of WSSs to glucose and LA. A three-step degradation scheme reflecting the main pathways of MCC degradation in the reaction is proposed.

A solid acid catalyst (HA–CC–SO3H) was synthesized by the sulfonation of amorphous carbon derived from the carbonization of dilute hydrochloric acid-pretreated microcrystalline cellulose. It was found that Cl− ions are grafted onto the cellulose-derived carbon and affect the composition and structure of the carbon carrier during the carbonization process. The electrons of the aromatic carbons transfer to –Cl and –SO3H groups, which influence their electronic state. In the cellulose hydrolysis process, the active electronic states make the –Cl groups more liable to form hydrogen bonds with cellulose, and the –SO3H groups with stronger acidity easily break the glycosidic bonds of cellulose to produce glucose. The HA–CC–SO3H catalyst exhibits excellent glucose selectivity (95.8%) at a moderate temperature (155 °C) under hydrothermal conditions.

•(Ag, S)-modified TiO2 photoanodes were prepared using natural garlic as a sulfur source.•Modification widened light absorption in UV–vis light and promoted electron transport.•Modification can improve the efficiency of the DSSC.The (Ag, S)-modified TiO2 photoanodes were prepared using novel garlic (Allium sativum) as a sulfur source. X-ray photoelectron spectroscopy (XPS) confirmed more sulfur adsorption and the modification of TiO2 by interactions between Ag and S. UV–vis spectral analysis and Electrochemical Impedance Spectroscopy (EIS) measurements showed that (Ag, S)-modified TiO2 photoanodes exhibited a strongly enhanced absorption in the UV–vis region and a clear reduction in charge transport resistance, indicating a higher light-harvesting capacity and more efficient charge transport. Therefore, the photoelectric conversion efficiency of dye-sensitized solar cells (DSSCs) was improved. At the optimal Ag loading of 0.5 wt%, (Ag, S)-modified DSSC gave the best performance.

A novel biomass-coated Ag nanoparticle-modified TiO2 composite was prepared and used as a photoanode in a dye-sensitized solar cell with a high surface area, strong light scattering and efficient electron transport. It was found that syzygium extract has an appreciable effective function as a reducing and stabilizing agent simultaneously. The mean size of the synthesized silver nanoparticles is 4.0 ± 0.7 nm measured on the TEM images. Residual hydroxyl groups of the biomass on the photoanode improve dye absorption and electron injection efficiency. The syzygium-Ag–TiO2 DSSC exhibits the best performance with a short-circuit current of 11.8 mA cm−2 corresponding to a photoelectric conversion efficiency of 5.12%, which is higher than the glucose-Ag–TiO2 and UV-Ag–TiO2 DSSCs, and much higher than the blank DSSC.

The photocatalytic activity for H2 evolution from pure water over Pd loaded TiO2 prepared by gardenia extract (Pd-Gardenia-TiO2) is systematically investigated. The as-prepared photocatalysts are characterized by X-ray diffraction, high resolution transmission electron microscopy, Fourier transform infrared spectra, and X-ray photoelectron spectroscopy. Gardenia extract functions as reducing and stabilizing agents simultaneously. The mean size of the as-prepared Pd nanoparticles is in the range of 2.3 ± 0.5 nm based on TEM images. The Pd-Gardenia-TiO2 catalyst exhibits good photocatalytic activity for H2 evolution (93 μmol · h−1 · g−1), which is much higher than that of Pd photodeposited on TiO2. Possible factors for its photocatalytic activity from pure water are also investigated.Highlights► Photoactivity for H2 evolution from pure water over Pd-Gardenia-TiO2 is studied. ► The mean size of the as-prepared Pd nanoparticles is 2.3 ± 0.5 nm. ► The introduction of gardenia extract is beneficial to enhance the photoactivity. ► Pd-Gardenia-TiO2 shows much higher photoactivity than Pd photodeposited on TiO2.

Perovskite-like oxides LaNi1−xCuxO3 (x = 0.1, 0.4, 0.5) were prepared by means of the citric acid complexing method. TPR revealed the incorporation of Cu into the perovskite lattice increased the reducibility of the catalyst. After LaNi1−xCuxO3 were pretreated in H2 for 2 h at certain low temperature, the material still retained its perovskite structure and oxygen vacancies were generated in the lattice. DRS showed that narrowing of band-gap of reduced LaNi1−xCuxO3 was governed by the crystalline structure and the defect in the catalyst. In the photocatalytic water splitting experiment, 200 and 250°C-reduced LaNi0.6Cu0.4O3, 200°C-reduced LaNi0.5Cu0.5O3 possessed the high and colse catalytic activity. XPS showed that the molar ratio of Cu2+/Cu1≈1 and lattice oxygen/adsorb oxygen ≈ 0.2 in the catalysts had high catalytic activity. According to the outcome of our experiments, we conclude that there is a balance relation either between oxygen vacancies and catalytic activity or between Cu2+/Cu1+ redox couples and catalytic performance of these materials for hydrogen production from photocatalytic water splitting. Enhancement of hydrogen yield can be attributed to the small band-gap and the lowering the recombination probability for electron-hole pairs.

To accrue the full environmental benefit of hydrogen as an energy carrier, we need to develop new visible-light-active photocatalyst. Here, the LaNi0.7Cu0.3O3, was used as a precursor and then treated at various temperatures (523–673 K) for 2 h under continuous H2 flow. Among all the resultant photocatalysts, the LaNi0.7Cu0.3O3 treated at 573 K, exhibited highest photocatalytic activity when exposed to visible-light irradiation. We characterized the samples by XRD, DRS, XPS and PL. It was found that a perovskite-related material with proper oxygen vacancies and Cu2+/Cu1+ redox couples facilitated the enhancement in photocatalytic activity.

In this paper we studied the adsorption and desorption behavior of SO2 by the dead Bacillus licheniformis R08 biomass. The effects of water vapor, temperature and O2 on the removal of SO2 by the biomass were studied. FTIR and XPS were used to characterize the mechanism of the SO2 adsorption on the biomass. The experimental results showed that water vapor and temperature deeply influenced the adsorption of SO2 by the biomass. However, O2 cannot oxidize SO2 to SO3 on the biomass. FTIR and XPS results showed that oxygenous and nitrogenous functional groups on the cell walls of biomass may be related to the SO2 adsorption and three sulfur species were formed on the biomass in adsorption process. In the desorption process, weakly adsorbed SO2 could be desorbed by increasing temperature and the biomass can be reused for 10 cycles.

A new cuprous adsorbent was prepared by bioreduction method with biomass R08 and its desulfurization ability and regenerative property at low temperature were studied. The results indicated that the amount of SO2 adsorbed on the adsorbent was lower than that on Cu/γ-Al2O3 prepared by chemical method at low temperature; however, it can be easily regenerated and the regenerative adsorbent still has a good SO2 adsorption ability, higher than 87% of that in fresh adsorbent after six regenerations. XPS and FTIR analysis showed that biomass can reduce Cu2+ to Cu+ by aldose and keep the valence of copper exposed to O2 and H2O atmosphere. Furthermore, SO2 is adsorbed on the sorbent with chemical complexation bonds so that it can be desorbed by increasing temperature which is different from γ-Al2O3, Cu(II)/γ-Al2O3 and Cu(I)/γ-Al2O3 that sulfate species are formed.

In this study, LaNiO3 perovskite catalysts were prepared by citrate method and used for carbon dioxide (CO2) methanation. The catalysts were activated at different temperatures (400–700°C) under the reactant stream. The activation led to the formation of small metallic nickel particles and hexagonal lanthanum oxocarbonate (La2O2CO3). Ni0 was highly dispersed and enveloped by La2O2CO3, which was responsible for the high catalytic activity and stability of the LaNiO3 perovskite catalysts even at high temperature (400–500°C). The X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and H2-temperature-programmed desorption measurements illustrated that La2O2CO3 generated from the activation might play an important role in the methanation of CO2.

We reported a novel method to promote the growth of microalgae Dunaliella bardawil (D. bardawil) and disrupt the structure of microcrystalline cellulose (MCC) by adding different amount of MCC to the growth medium (200 mL). The effect of MCC additive on the growth of D. bardawil was examined, and structure changes of MCC treated in the medium were investigated. The proper addition of MCC promoted the growth of D. bardawil by removing some growth inhibitors derived from algae exudates in the medium. Cell density of the algae got a maximum increase of about 20% when MCC was added at 1.5 g/L. After treatment in the medium, MCC had the maximum reduction 12.5% in crystallinity (CrI), and polymerization degree (DP) was reduced to the minimum 170 from 209, leading to a lower thermal stability. All the above changes of treated MCC can be attributed to the combined effects of algae exudates and inorganic ions in the medium. We believe that this study has potential value in making the two biological resources more suitable for utilization.Graphical abstractDownload full-size imageHighlights► Microcrystalline cellulose can remove growth inhibitors derived from algae exudates. ► Disruption of cellulose occurs in the algae culture medium. ► There are connections between growth of algae and disruption of cellulose.

C and Fe co-doped LaCoO3 were prepared by citric acid and Bacillus licheniformis R08 biomass co-chelate method. The characterization results demonstrated that the optical response of LaCoO3 was red-shifted to the visible-light region with the introduction of C and Fe. Carbon was substituted for lattice oxygen atoms in the LaCoO3; Fe doping could form a dopant energy level above the valence band of LaCoO3. The photocatalytic tests indicated that the C–LaCo0.95Fe0.05O3 catalyst showed high activity for the reduction of carbon dioxide under visible-light irradiation, assigned to the synergistic effect of doped carbon and ferric.