Preparation Of Energy Materials Based On Seaweed Fiber Raw Materials And Study Of Structural Properties

Recently, abundant sea biomass resources have becoming more and more attractive because of their potential application in the renewable energy. Alginate is naturally derived linear copolymer, which the negatively charged framework(–COO–) in G-rich blocks of the alginate polymers makes it simple to form metal alginates(M-alginates) by absorbing Mx+, and their structures have been described by the so-called “egg-box”structure. Alginate is fantastic precursors of nanotextured carbons, which is a promising candidate as carbon-based electrode materials for energy storage. The alginate could prepare micron- and nano-sized alginic fibers through wet-spinning and electrospinning,respectively. Herein, we demonstrate Co3O4/C fibers(Co3O4-CF) and nitrogen-doped porous carbon nanofibers(N-PCNFs) by pyrolyzing alginic fibers and test the electrochemical performance for lithium ion batteries(LIBs), supercapacitors(SCs), and oxygen reduction reaction(ORR).Firstly, after carbonization of the Co-alginates in inert gas atmosphere, it is expected to obtain Co3O4-CF, where the Co3O4 can be encapsulated well by the carbonized alginate.Apparently, this simple strategy is more feasible to synthesize a stable Co3O4/C battery anode compared with the complicated conventional methods. This nano/microstructure can combine the merits of the Co3O4 nanostructure and the carbonaceous microfibre matrix, and thus exhibits a high reversible capacity of 780 mAh/g at 89 mA/g after 100 cycles using as anode materials as well as excellent cycling stability and rate performance.Secondly, we prepared a unique sustainable biomass conversion strategy for N-PCNFs through pyrolyzing the electrospinning renewable natural alginate as high-performance multifunctional energy materials for boosting the performance of LIBs,SCs, and ORR. The N-PCNFs owned high specific surface area, good electrochemical conductivity, porous structure, and partly graphitization. Those features can promote the fase electron transform and efficient ions diffusion. We found that the N-PCNFs pyrolyzed at 600 °C(denote as N-PCNFs-600) in the ammonia show the optimal structure and electronic characteristics, making them exhibit a large reversible capacity of 625mAh/g at 1 A/g, good rate capability(175 mAh/g at 20 A/g) and excellent cycling performance for LIBs, which are among the best in all the reported carbon nanomaterials.It also represents among the best highly efficient carbon materials for SCs with excellentcapacitive behavior of 197 F/g at 1 A/g and superior stability. Most importantly, the N-PCNFs-600 can act as a metal-free catalyst for ORR with same half-wave potential and onset potential as those of Pt/C, much better long-term stability, and methanol tolerance than Pt/C via a four-electron pathway in alkaline medium.