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In the life cycle assessment of bioethanol processes under choline chloride/urea (DES-U), choline chloride/lactic acid (DES-LA) and sodium hydroxide (NaOH) pretreatment studied. As the net energy values under DES-U, DES-LA pretreatment was negative, which were − 4,107,023 MJ and − 643,449 MJ, respectively; they could not get positive energy benefits. High solid loading pretreatment could directly reduce the total net energy input. The net energy ratios of DES-U and DES-LA were 0.00644, which were much lower than 1.01 of NaOH. The renewability of DES-U and DES-LA were 0.0412 and 0.0414, respectively, which were much lower than NaOH (1.24). Renewability under three pretreatments was increased in the cases of predominantly lignin-rich residue supply. The coal consumption of DES pretreatment was more than 1.93 times NaOH, resulting in high CO 2 emission. The coefficients for greenhouse gas emissions (GHG), ozone depletion and fossil depletion of three pretreatments were less than 1 %, with high confidence. For NaOH, DES-U, DES-LA, the GHG emissions were assessed to be 10,278.8, 12,801.8 and 8528.3 kg CO2 eq., respectively. When lignin residue instead of coal was used as energy supply raw material, GHG emission of NaOH, DES-U, DES-LA processes decreased insignificantly, which reduction were 33.3 %, 33.4 % and 28.4 % for kg CO2eq. • High solid loading pretreatment could achieve positive benefits. • The environmental emissions of Alkali pretreatment had low emission levels. • DES pretreatment had the low value for the environmental impact category. • Lignin-rich residues supply could significantly reduce environmental impact. • high fermentation efficiency could improve the environmental friendliness. [ABSTRACT FROM AUTHOR]

N-doped carbon materials represent promising metal-free electrocatalysts for the oxygen reduction reaction (ORR), the cathode reaction in fuel cells, metal-air batteries, and so on. A challenge for optimizing the ORR catalytic activities of these electrocatalysts is to tune their local structures and chemical compositions in a rational and controlled way that can achieve the synergistic function of each factor. Herein, we report a tandem synthetic strategy that integrates multiple contributing factors into an N-doped carbon. With an N-containing MOF (ZIF-8) as the precursor, carbonization at higher temperatures leads to a higher degree of graphitization. Subsequent NH 3 etching of this highly graphitic carbon enabled the introduction of a higher content of pyridine-N sites and higher porosity. By optimizing these three factors, the resultant carbon materials displayed ORR activity that was far superior to that of carbon derived from a one-step pyrolysis. The onset potential of 0.955 V versus a reversible hydrogen electrode (RHE) and the half-wave potential of 0.835 V versus RHE are among the top ranks of metal-free ORR catalysts and are comparable to commercial Pt/C (20 wt %) catalysts. Kinetic studies revealed lower H 2 O 2 yields, higher electron-transfer numbers, and lower Tafel slopes for these carbon materials compared with that derived from a one-step carbonization. These findings verify the effectiveness of this tandem synthetic strategy to enhance the ORR activity of N-doped carbon materials., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)