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Lignocelluloses have been the focus of much attention, because of their conversion to fermentable sugars for cellulosic ethanol production, both from the viewpoint of energy and the environment. Pretreatment plays a crucial rule in biomass conversion, to overcome the chemical and structural difficulties, which have evolved in lignocelluloses, and to produce a cost-effective fermentable sugar via enzymatic saccharification. Among the developed pretreatment approaches, alkali-based pretreatment technology, which can utilize the equipment and chemical recovery system in the pulping industry, has been considered one of the most promising pretreatment methods, mainly because of its high efficiency in delignification and high final total sugar yields. This paper reviews the classification, mechanism, advantages, disadvantages, and the progress of alkali-based pretreatment technologies, in order to better understand the fundamental principles of alkali-based pretreatments. This is of vital importance for the process improvement and commercial production of alkali-based pretreatment for producing cellulosic ethanol.

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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 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 O 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.

Hybrid bio-inorganic microbeads composed of CRGO–enzyme and alginate exhibited better stability and higher environmental tolerance, which can be used in a continuous fixed-bed enzymatic reaction.