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Electrosynthesis of hydrogen peroxide via oxygen reduction reaction's two-electron route is the potential alternative to the industrial anthraquinone process for being green and cost-effective. Whereas oxygen-doped graphitic carbons have been reported as efficient catalysts, two issues remained unsettled involving usually abundant carbon-basal-planes and a mixture of oxygen functional groups, which lower the efficiency due to massive inactive planes and functional groups. To achieve carbon-based catalysts with abundant edges and identical functional groups, a 'bottom-up' approach to design materials at the molecular level is presented here. Starting from the small molecules of pyrene, a microporous carbon framework is prepared with abundant micropores of 0.5 nm and a large surface area up to 1346 m2 g-1, which facilitates further combination of a high content of C–O–C with the rich carbon edges. The positive correlation between selectivity and oxygen content further confirms the C–O–C as active sites. The catalyst exhibits a comprehensive performance including a considerable selectivity of 87%, a low onsite-potential at 0.77 V RHE , and a high ring current density of 2.79 mA cm−2 at 0.42 V RHE. Such a 'bottom-up' structural and functional engineering strategy may extend to the synthesis of more catalysts/electrode materials and energy/environmental related applications. Image 1 • A 'bottom-up' approach was used to make carbon-based catalysts with rich edge-defects, porous structure, and C-O-C groups. • The positive correlation between selectivity and C–O–C content confirmed the C–O–C groups as identical active sites. • The as-made catalyst showed considerable selectivity towards H 2 O 2 production of 87%, long-term catalytic stability over 10 h, low onsite-potential of 0.77 V, and a high ring current of 2.7mAcm−2. [ABSTRACT FROM AUTHOR]

The batch and fed-batch tests were performed to evaluate the efficiency of bioaugmentation in combination with biostimulation for remediation of paddy soil contaminated with 2,4-dichlorophenoxyacetic acid (2,4-D). 2,4-D degrading enrichments were used for bioaugmentation, and effluents prepared through biological hydrogen production process were used as substrate for biostimulation. The batch tests indicated that 2,4-D degradation depended on the enrichment/substrate ratio (E/S), where E/S of 0.03 showed an excellent performance. The fed-batch tests showed that biostimulation only led to an improvement in 2,4-D degradation, while the pattern of repeated augmentation of enrichments (FRA) together with biostimulation obviously improved degradation of 2,4-D, 2-chlorophenol (2-CP) and phenol. DNA-sequencing approach showed that the FRA pattern altered the bacterial community composition, and high removal of 2,4-D, 2-CP and phenol may be attributed to the acclimation and persistence of Thauera . The findings demonstrated the importance of the FRA pattern on remediation of paddy soil contaminated with 2,4-D. [ABSTRACT FROM AUTHOR]

Potential for paddy soil enrichments obtained in the presence of nano-sized magnetite particles (named as PSEM) to promote methane production from effluents of hydrogen-producing stage in two-stage anaerobic digestion was investigated. The results showed that the addition of magnetite significantly accelerated methane production from acetate in a dose-independent manner. The results from high-throughput sequencing analysis revealed that Rhodocyclaceae -related species were selectively enriched, which were likely the key players for conversion of acetate to methane in PSEM. Compared to the paddy soil enrichments obtained in the absence of magnetite (named as PSEC), the maximum methane production rate in PSEM was significantly higher (1.5–5.5 times higher for the artificial medium and 0.2–1.7 times higher for the effluents). The accelerated methane production from the effluents indicated remarkably application potential of PSEM for improving performance of anaerobic digestion. [ABSTRACT FROM AUTHOR]

In the reaction system with NaBH 4 as a hydrogen donor, inhibiting the formation of hydrogen is the key to promote the efficient catalytic hydrogenation of CO 2. In this study, nanoscale zero-valent nickel supported on carbon nanofibers (Ni0/CNFs) was fabricated as a catalyst for CO 2 hydrogenation in aqueous NaBH 4 solution. The characteristics of Ni0/CNFs were examined. By SEM, it was observed that spherical nickel nanoparticles were distributed homogeneously on the surface of strip-shaped carbon nanofibers. EDS mappings indicated that elements were evenly distributed on the catalyst, which might contribute to the uniform exposure of active sites. Via XRD, it was determined that all the diffraction peaks corresponded to the crystal face of nickel metal and that the absence of diffraction peaks of carbon nanofibers indicated that the crystallinity of the carrier was low. XPS study showed that nickel existed on the catalyst surface in two forms: zero valence metal and oxidation state. The effects of catalyst addition amount, NaBH 4 concentration, NaOH dosage, stirring rate on the yield of formate and hydrogen generation rate (HGR) were investigated. By optimizing the above parameters, the concentration of formate reached 150 mmol/L and the hydrogen production rate was 10.55 mL/min. Compared with the non-catalytic conditions, the concentration of formate increased by 57 % and the HGR decreased by 78 %. Moreover, the relationship between CO 2 hydrogenation and NaBH 4 hydrolysis was clarified. This research could enhance comprehension of CO 2 hydrogenation in aqueous NaBH 4 solution and contribute to the development of CO 2 capture and utilization storage technology. The significance of this study lies in clarifying the connection between CO 2 hydrogenation and borohydride hydrolysis in CO 2 catalytic hydrogenation technology. • Ni0/CNFs promoted CO 2 catalytic hydrogenation by inhibiting NaBH 4 hydrolysis. • The relationship between CO 2 hydrogenation and NaBH 4 hydrolysis was clarified. • Catalytic hydrogenation of CO 2 was performed under ambient conditions. [ABSTRACT FROM AUTHOR]

Using batch and repeated batch cultivations, this study investigated the effects of bioaugmentation with enriched microbial consortia (named as EMC) on methane production from effluents of hydrogen-producing stage of potato slurry, as well as on the indigenous bacterial community. The results demonstrated that the improved methane production and shift of the indigenous bacterial community structure were dependent on the EMC/sludge ratio and bioaugmentation patterns. The methane yield and production rate in repeated batch bioaugmentation pattern of EMC were, respectively, average 15% and 10% higher than in one-time bioaugmentation pattern of EMC. DNA-sequencing approach showed that the enhanced methane production in the repeated batch bioaugmentation pattern of EMC mainly resulted from the enriched iron-reducing bacteria and the persistence of the introduced Syntrophomonas , which led to a rapid degradation of individual VFAs to methane. The findings contributed to understanding the correlation between the bioaugmentation of microbial consortia, community shift, and methane production. [ABSTRACT FROM AUTHOR]

Abstract: The conversion of lipid-extracted microalgal biomass residues (LMBRs) into hydrogen plays the dual role in renewable energy production and sustainable development of microalgal biodiesel industry. An anaerobic fermentation process to covert LMBRs into hydrogen was investigated in this work. Using batch experiments, the effects of pretreatment of inoculum (by acid, base, heat, and chloroform, respectively), initial pH (5.0–7.0), inoculum concentrations at 0.59–2.94gVSS/l (volatile suspended solids, VSS) and substrate concentrations at 4.5–45gVS/l (volatile solids, VS) were investigated, respectively. The results showed that the most effective hydrogen production was obtained from fermentation of LMBRs with a concentration of 36gVS/l at the initial pH 6.0–6.5 using the heat-treated anaerobic digested sludge as inoculum. Acetate, propionate and butyrate were the main fermentation byproducts in the conversion of LMBRs into hydrogen. [Copyright &y& Elsevier]

Abstract: A two-stage process to produce hydrogen and methane from lipid-extracted microalgal biomass residues (LMBRs) was developed. The biogas production and energy efficiency were compared between one- and two-stage processes. The two-stage process generated 46 ± 2.4 mL H2/g-volatile solid (VS), and 393.6 ± 19.5 mL CH4/g-VS. The methane yield was 22% higher than the one in the one-stage process. Energy efficiency increased from 51% in the one-stage process to 65% in the two-stage process. Additionally, it was found that repeated batch cultivation was a useful method to cultivate the cultures to improve the methane production rate and reduce the fermentation time. In the repeated batch cultivation, the methane yield slightly decreased if the ammonia levels rose, suggesting that the accumulation of ammonia could affect methane production. [Copyright &y& Elsevier]

Abstract: Energy recovery from lipid-extracted microalgal biomass residues (LMBRs) plays a significant role in the sustainable development of the microalgal biodiesel industry. Different methods were used to pretreat LMBRs to improve their solubilization and anaerobic hydrogen production abilities. The pretreatment methods studied included thermal (100 °C and 121 °C), alkaline and thermo-alkaline pretreatments (combinations of alkaline and thermal pretreatments). The results showed that thermo-alkaline pretreatments resulted in remarkable improvements of LMBR solubilization, which led to an increase in hydrogen yield. The highest hydrogen yield of 45.54 mL/g-volatile solid (VS) was achieved from LMBRs pretreated by the thermo-alkaline pretreatment at 100 °C, which was approximately three-fold higher than the yield from untreated LMBRs. The results of this study proved that thermo-alkaline pretreatment at 100 °C is an effective method to improve LMBR solubilization and increase the hydrogen production from LMBRs. [ABSTRACT FROM AUTHOR]

This research aims to identifying the potential effect of using a hydrogen-producing reactor’s effluent as an enrichment amendment for enhancing the degradation rates of 2,4-dichlorophenoxyacetic acid (2,4-D) during the bioremediation of contaminated paddy soils. The results showed that addition of the effluents to 2,4-D- degrading enrichment culture enhanced (up to 1.3-fold) the degradation rate constant of 2,4-D. The enhancement effect most probably resulted from the co-metabolic degradation of 2,4-D facilitated by volatile fatty acids (e.g., acetate, propionate, and butyrate) in the effluents which served as the beneficial substrates. Results from DNA sequencing analysis showed that the effluent additions shifted the bacterial community composition in the enrichment culture. Dechloromonas and Clostridium were two dominant bacterial genera involved in 2,4-D degradation. The findings will make a substantial contribution to remediation of soils contaminated with 2,4-D. [ABSTRACT FROM AUTHOR]