磷掺杂MnO2电极材料的制备及电容性能

Preparation and capacitive properties of phosphorus-doped MnO2 electrode materials

摘要:

MnO2因其高理论容量被认为是具有发展前景的超级电容器(SCs)电极材料，但MnO2材料普遍存在结构稳定性较差、Mn2+易溶解和导电性差等问题限制了其应用。利用KMnO4、MnSO4?H2O和NaH2PO2?H2O一步水热法在泡沫镍基底上成功制备自支撑磷掺杂MnO2纳米材料(Px-MnO2)（x表示NaH2PO2?H2O的质量，分别为0.017，0.051和0.085），通过使用SEM、TEM、XRD和XPS等技术对其形貌结构和化学成分进行分析，证实磷的成功掺杂。以Px-MnO2为工作电极，在2 mol/L KOH电解液中，通过三电极体系测试其电化学性能。当扫描速率从5 mV/s增加至50 mV/s时，其CV曲线形状无明显变化，说明其具有较好的电化学可逆性。通过增加参与反应的磷源质量，电极材料的比电容呈先增后减趋势，其中电极材料P0.051-MnO2的放电时间最长，证明比电容性能最佳。在1 A/g的电流密度下，P0.051-MnO2的比电容为342 F/g，优于MnO2电极(90 F/g)、P0.017-MnO2(217 F/g) 和P0.085-MnO2(169 F/g)，当电流密度升高至10 A/g时，P0.051-MnO2电极的比电容为262.3 F/g，说明具有良好的倍率性能（容量保持率为76.7%）；P0.051-MnO2在循环2000圈后，容量保持率仍为94.3%，说明具有较好的循环稳定性。EIS测试结果表明Px-MnO2相较于MnO2具有更小的体系欧姆电阻和扩散电阻。根据电极动力学分析，相对于MnO2，同一扫速下P0.051-MnO2的电容控制占据更大的比例，说明磷掺杂可有效增强MnO2的电荷迁移能力，产生更多的活性位点，提升其电容性能，这为优化MnO2的电化学性能提供了可行策略。

Abstract:

To enhance the structural stability of MnO2 materials and address issues such as the solubility of Mn2+ and poor conductivity, NaH2PO2·H2O was utilized as a phosphorus source, while nickel foam (NF) served as the current collector. A self-supporting phosphorous-doped MnO2 nanomaterial was successfully synthesized on the NF substrate through a one-step hydrothermal method using KMnO4 and MnSO4·H2O. The morphology, structure, and composition of the resulting material were characterized by SEM, TEM, XRD, and XPS techniques. The electrochemical performance of phosphorus-doped MnO2 was evaluated using a three-electrode system, focusing on the impact of varying amounts of NaH2PO2·H2O additive on the capacitance properties of the phosphorus-doped MnO2 electrode. The results indicate that NaH2PO2·H2O was successfully synthesized with mass additions of 0.017 g, 0.051 g, and 0.085 g to produce three types of phosphorus-doped MnO2: P0.017-MnO2, P0.051-MnO2, and P0.085-MnO2. When the scan rate increased from 5 mV/s to 50 mV/s, all three phosphorus-doped MnO2 electrodes exhibited good electrochemical reversibility. Notably, the P0.051-MnO2 electrode demonstrated the longest discharge time (232 s) and optimal capacitance performance; this may be attributed to its larger specific surface area (236.6864 m2/g) and nanoparticle structure. At a mass current density of 1 A/g, the mass specific capacitance of P0.051-MnO2 electrode is 342 F/g, which is better than that of MnO2 electrode (90 F/g), P0.017-MnO2 electrode (217 F/g) and P0.085-MnO2 electrode (169 F/g). When the mass current density is increased to 10 A/g, the specific capacitance of P0.051-MnO2 electrode is 262.3 F/g, and the capacity retention rate is 76.7%. The capacity retention rate of P0.051-MnO2 electrode was 94.3% after 2000 cycles. The P0.051-MnO2 electrode has a smaller system ohm resistance (about 0.9 Ω) and diffusion resistance (about 0.2Ω) in electrochemical impedance (EIS) testing. When the scanning rate is 50 mV/s, the capacitance contribution rate of P0.051-MnO2 electrode is 87%, which is higher than that of MnO2 electrode 71%. Phosphorus doping can effectively enhance the charge transfer ability of MnO2, generate more active sites, and improve its capacitive performance.