Dong Yan,Shuhao Xiao,Xinyan Li,Rui Wu,Jinxia Jiang,Xiaobin Niu,Jun Song Chen
Graphical Balancing act : Boron-doped Na 3 V 2 (PO 4 ) 3 is synthesized through a facile electrospinning method. NVP@carbon with a balanced content of BCO 2 and BC 2 O exhibits the best sodium storage properties. BC 2 O mainly improves the sodium diffusion and BCO 2 enhances the structural stability. Na 3 V 2 (PO 4 ) 3 (NVP) is a widely studied cathode material for sodium-ion batteries because of its high ionic conductivity and attractive charge/discharge plateau (3.4 V vs. Na/Na + ). However, its poor electronic conductivity and severe volume expansion during sodium storage need to be addressed before its intensive application could be realized. Herein, boron-doped NVP was synthesized through a facile electrospinning method. By adding boric acid into the reaction mixture during electrospinning followed by carbonization, boron could be directly inserted into the carbon matrix, giving rise to B-doped carbon nanofiber wrapped NVP. By tuning the doping amount, the boron-containing configurations could be facilely manipulated, playing different roles in promoting the sodium storage properties of the composite. Based on the calculation results, BC 2 O enhanced sodium diffusion by lowering the energy barrier, while BCO 2 improved the structural stability. Due to these specific functionalities of the configurations, the as-prepared composite with a balanced amount of BC 2 O and BCO 2 demonstrated superior sodium storage capacity of 113 mAh g −1 at 1 C, outstanding long cycling performance of 103 mAh g −1 at 10 C, and retained 91 mAh g −1 after 1500 cycles. This gave rise to a capacity loss of only 0.08‰ per cycle, much better than the undoped counterpart.
Ambiguous interpretations regarding the underlying mechanism of molecular oxygen (O 2 ) activation by the carbonaceous material/reductant system, especially in terms of the catalytic active site, have impeded the optimization and broader application of the system in environmental remediation. Here, we thoroughly investigated the role of boron-doped biochar (BBC) active sites in O 2 activation and optimized the ascorbic acid (AA) dosing strategy to improve the hydroxyl radical (•OH) production rate and pollutant removal. The introduction of boron facilitated O 2 activation through the successive one-electron transfer to generate •OH that predominantly occurred and accumulated on BBC surface, where •OH yield was nearly 5-fold and 9-fold higher than that in N-doped biochar/AA and zero-valence iron (ZVI) system, respectively. This results in better degradation performance of BBC/AA system for organic pollutants absorbed on the BBC surface and robust resistance to commonly occurring water anions and negatively charged organic matter. Moreover, the stepwise addition of low-concentration AA (0.5 mM) promoted the BPA removal (over 90 %) by maximizing the effective availability of AA and •OH. Characterization, galvanic oxidation process, and theory calculation results revealed that BC 2 O acted as the primary electron-accepting group to receive the electrons from AA, while BC 3 acted as both an electron-donating group and an O 2 adsorption site on BBC, which together facilitated O 2 activation and •OH production on the BBC surface. These findings provide a comprehensive understanding of O 2 activation within the BBC/AA system, highlighting its potential as a sustainable and effective approach for advanced environmental remediation applications.
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