Salt-Induced Phase Separation to Synthesize Ordered Mesoporous Carbon by pH-Controlled Self-Assembly

Self-assemly of block copolymers (BCPs) and phenolic resin (PR) is an important method to prepare ordered mesoporous polymers (OMPs) and carbon materials (OMCs). In the process, phase separation of the BCP–PR composite is a critical step which is, however, time-consuming in aqueous solution. Here we report, for the first time, a new salt-induced phase separation strategy to achieve this goal. Triblock copolymer F127 and phenol-formaldehyde resin (PF) are used as the template and precursor, respectively, and sodium chloride (NaCl) is applied to induce the coagulation and phase separation of the F127–PF composite which is transformed to be OMC at high temperature. It is found that the maintenance of the ordered mesostructure is highly dependent on the pH of the F127–PF solution under NaCl interference. A hypothetical mechanism is proposed to explain the role of pH in the formation of ordered mesostructure when salt is introduced into the self-assembly system. The effects of pH, salt concentration, and varied salts on the structures and properties of the as-prepared OMCs are investigated in detail. The new salt-induced phase separation strategy can synthesize OMC facilely and can provide a new insight into understanding the process of preparing ordered mesoporous materials by self-assembly more deeply

Direct Synthesis of Nitrogen-Doped Carbon Nanosheets with High Surface Area and Excellent Oxygen Reduction Performance

Graphene-like nitrogen-doped carbon nanosheets (NCN) have become a fascinating carbon-based material for advanced energy storage and conversion devices, but its easy, cheap, and environmentally friendly synthesis is still a grand challenge. Herein we directly synthesized porous NCN material via the facile pyrolysis of chitosan and urea without the requirement of any catalyst or post-treatment. As-prepared material exhibits a very large BET surface area of ∼1510 m² g^–1 and a high ratio of graphitic/pyridinic nitrogen structure (2.69 at. % graphitic N and 1.20 at. % pyridinic N). Moreover, compared to a commercial Pt/C catalyst, NCN displays excellent electrocatalytic activity, better long-term stability, and methanol tolerance ability toward the oxygen reduction reaction, indicating a promising metal-free alternative to Pt-based cathode catalysts in alkaline fuel cells. This scalable fabrication method supplies a low-cost, high-efficiency metal-free oxygen reduction electrocatalyst and also suggests an economic and sustainable route from biomass-based molecules to value-added nanocarbon materials