A Crystalline Copper(II) Coordination Polymer for the Efficient Visible-Light-Driven Generation of Hydrogen.

A crystalline coordination polymer (CP) photocatalyst (Cu-RSH) which combines redox-active copper centers with photoactive rhodamine-derived ligands remains stable in acid and basic solutions from pH 2 to 14, and efficiently catalyzes dihydrogen evolution at a maximum rate of 7.88 mmol g(-1) h(-1) in the absence of a mediator and a co-catalyst. Cyclic voltammetry, control experiments, and DFT calculations established that copper nodes with open coordination sites and favorable redox potentials, aided by spatially ordered stacking of rhodamine-based linkers, account for the high catalytic performance of Cu-RSH. Emission quenching, time-resolved fluorescence decay, and transient photocurrent experiments disclosed the charge separation and transfer process in the catalytic system. The present study demonstrates the potential of crystalline copper CPs for the practical utilization of light.

Effective conversion of maize straw wastes into bio-hydrogen by two-stage process integrating H2 fermentation and MECs.

The enhanced H2 production from maize straw had been achieved through the two-stage process of integrating H2 fermentation and microbial electrolysis cells (MECs) in the present work. Several key parameters affecting hydrolysis of maize straw through subcritical H2O were optimized by orthogonal design for saccharification of maize straw followed by H2 production through H2 fermentation. The maximum reducing sugar (RS) content of maize straw reached 469.7 mg/g-TS under the optimal hydrolysis condition with subcritical H2O combining with dilute HCl of 0.3% at 230 °C. The maximum H2 yield, H2 production rate, and H2 content was 115.1 mL/g-TVS, 2.6 mL/g-TVS/h, and 48.9% by H2 fermentation, respectively. In addition, the effluent from H2 fermentation was used as feedstock of MECs for additional H2 production. The maximum H2 yield of 1060 mL/g-COD appeared at an applied voltage of 0.8 V, and total COD removal reached about 35%. The overall H2 yield from maize straw reached 318.5 mL/g-TVS through two-stage processes. The structural characterization of maize straw was also carefully investigated by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) spectra.

Direct degradation of cellulosic biomass to bio-hydrogen from a newly isolated strain Clostridium sartagoforme FZ11.

A mesophilic hydrogen-producing strain, Clostridium sartagoforme FZ11, had been newly isolated from cow dung compost acclimated using microcrystalline cellulose (MCC) for at least 30 rounds in an anaerobic bioreactor, and identified by the 16S rDNA gene sequencing, which could directly utilized various carbon sources, especially cellulosic biomass, to produce hydrogen. The maximum hydrogen yields from MCC (10 g/l) and carboxymethyl cellulose (CMC, 10 g/l) were 77.2 and 64.6 ml/g, separately. Furthermore, some key parameters of affecting hydrogen production from raw corn stalk were also optimized. The maximal hydrogen yield and substrate degradation rate from raw corn stalk were 87.2 ml/g and 41.2% under the optimized conditions with substrate concentration of 15 g/l, phosphate buffer of 0.15 M, urea of 6 g/l and initial pH of 6.47 at 35 °C. The result showed that the strain FZ11 would be an ideal candidate to directly convert cellulosic biomass into bio-hydrogen without substrate pretreatment.

Direct bioconversion of raw corn stalk to hydrogen by a new strain Clostridium sp. FS3.

A new strain FS3 which could achieve an efficient bioconversion of raw corn stalk to hydrogen had been isolated from anaerobic acclimated sludge, and identified as Clostridium butyricum on the basis of a series of physiological and biochemical experiments and 16S rDNA gene sequence. The strain could utilize various carbon sources to produce hydrogen. On the basis of single-factor experiments, the response surface methodology (RSM) was performed to optimize the media for hydrogen production. The maximum hydrogen yield of 92.9ml/g was observed under the optimal conditions: 20g/l raw corn stalk, 1.76g/l NH4HCO3, 0.91g/l KH2PO4 and 10.4ml/l nutrient solution. This finding opens a new avenue for direct conversion of raw cellulosic biomass to bio-hydrogen.

Photocatalytic H2 generation based on noble-metal-free binuclear cobalt complexes using visible-light.

Two new binuclear cobalt complexes, namely {[Co(dmgH)(dmgH2)]2L1} (I) and {[Co(dmgH)(dmgH2)]2L2} (II) (dmgH = dimethylglyoximate monoanion; dmgH2 = dimethylglyoxime, L1 = 1,3-bis(4-pyridyl)propane), L2 = 1,3-bis(imidazol-1-ylmethyl)benzene), have been synthesized by the self-assembly of [Co(dmgH)(dmgH2)] and L1 or L2, respectively. An efficient photocatalytic system was constructed by combining a noble-metal-free cobalt complex as the catalyst with Eosin Y dye (EY(2-)) as the photosensitizer to give an efficient H2 generating system under visible-light irradiation (λ > 420 nm) using triethanolamine (TEOA) as a sacrificial electron donor. The maximum amount of H2 generated was 1013 TON for I and 1134 TON for II over a 2 h irradiation period (λ > 420 nm) under the conditions of pH 8.0, 5% TEOA (v/v), an EY(2-) concentration of 4.0 × 10(-4) M and a catalyst concentration of 4.0 × 10(-4) M in the mixed solvent system of CH3CN-H2O (3 : 1, v/v). In addition, the mechanism of H2 generation in the photolysis system was briefly discussed.

Anion exchange induced tunable catalysis properties of an uncommon butterfly-like tetranuclear copper(II) cluster and magnetic characterization.

An uncommon butterfly-like tetranuclear copper(ii) cluster with the formula {[Cu(4)(µ(3)-OH)(2)(µ(4)-Cl)(H(2)O)(2)(L)(2)]·Cl(H(2)O)(7)}(n) (1) (H(2)L = 1,2-bis[3-(1,2,4-triazolyl)-4-amino-5-carboxylmethylthio]ethane) has been synthesized. Compound 1 exhibits interesting anion exchange characteristics, in which both guest and coordinated Cl(-) can be replaced by I(-) or NO(3)(-) in water. Furthermore, a high catalytic selectivity to produce poly(phenylene ether) by the oxidative coupling of 2,6-dimethylphenol in water is found to be 74% for 1 and 87% for the anion-exchanged product 1-MI(x), respectively. Additionally, the antiferromagnetic interaction among Cu ions for compound 1 is also found.

[Enlargement test studies of bio-hydrogen production using artificial wastewater of corn stalk fermentation lixivium by mixed culture].

Conversion of artificial corn stalk wastewater, which was prepared according to the main composition of the corn stalk fermentation lixivium, into bio-hydrogen gas by mixed culture was performed in a 20 L half-continuous flow fermenter. The influences of several environmental factors on the bio-hydrogen production, such as HRT, C/N ratio, Fe2+ and artificial corn stalk wastewater concentration were discussed in the tests. The experimental results showed that HRT, C/N ratio, Fe2+ and artificial corn stalk wastewater concentration significantly affected the fermentation hydrogen production. The maximum H2 yield of 11.80 mol/kg, H2 concentration of 56% and hydrogen production rate of 8.81 L/(L x d) were obtained at HRT = 10 h, C/N = 100, Fe2+ concentration of 100 mg/L and substrate concentration of 12.5 g/L by mixed culture, respectively. In the fermentation hydrogen-producing process, the conversion efficiency of the substrate was more than 90%, and 39.40% of COD was removed from the reactor. The main by-products in the liquid phase were acetic acid, butyric acid, propionic acid and a little ethanol and butanol throughout this study.

Efficient conversion of wheat straw wastes into biohydrogen gas by cow dung compost.

Efficient conversion of wheat straw wastes into biohydrogen gas by cow dung compost was reported for the first time. Batch tests were carried out to analyze influences of several environmental factors on biohydrogen production from wheat straw wastes. The performance of biohydrogen production using the raw wheat straw and HCl pretreated wheat straw was then compared in batch fermentation tests. The maximum cumulative hydrogen yield of 68.1 ml H2/g TVS was observed at 126.5 h, the value is about 136-fold as compared with that of raw wheat straw wastes. The maximum hydrogen production rate of 10.14 ml H2/g TVS h was obtained by a modified Gompertz equation. The hydrogen content in the biogas was 52.0% and there was no significant methane observed in this study. In addition, biodegradation characteristics of the substrate were also discussed. The experimental results showed that the pretreatment of the substrate plays a key role in the conversion of the wheat straw wastes into biohydrogen by the composts generating hydrogen.