Electrochemistry and X-ray absorption spectroscopy (XAS) of MnO₂/reduced graphene oxide (RGO) were made to evaluate capacitive performance and electronic structure as a supercapacitor. MnO₂ was deposited on the surface of RGO by a spontaneous redox reaction. At low current density (1 A g⁻¹), the specific capacitance of MnO₂/RGO (MRGO) greatly increased with increasing growth time from 281 to 462 F g⁻¹. Electrochemical results show that the specific capacitance of RGO and MRGO arises from the combined contributions of electrochemical double-layer capacitance (EDLC) and pseudo-capacitance. To gain insights into the charge storage mechanism of RGO and MRGO, it was characterized using ex-situ soft XAS techniques at Mn L-edge and C, O K-edges in the charging/discharging process. The ex-situ soft XAS results provide evidence that the contribution of RGO to specific capacitance involves an oxygen-functionality-related contribution of pseudocapacitance and EDLC. In addition, the specific capacitance of MRGO reveals pseudocapacitive contributions from the redox processes that involve the Mn(III)/Mn(IV) redox reaction in MnO₂. This work utilizes electrochemical and ex-situ XAS techniques to elucidate charge storage mechanism for supercapacitor applications.

_{MnO 2} /还原氧化石墨烯（RGO）的电化学和X射线吸收光谱（XAS）被用来评估作为超级电容器的电容性能和电子结构。MnO ₂通过自发的氧化还原反应沉积在 RGO 的表面上。在低电流密度(1 A g ^-1 )下，MnO ₂ /RGO (MRGO)的比电容随着生长时间从281增加到462 F g ^-1大大增加。电化学结果表明，RGO和MRGO的比电容是由电化学双层电容（EDLC）和赝电容共同贡献的。为了深入了解 RGO 和 MRGO 的电荷存储机制，使用非原位对其进行了表征充放电过程中 Mn L-edge 和 C, O K-edges 的软 XAS 技术。异位软XAS结果证明 RGO 对比电容的贡献涉及赝电容和 EDLC 的氧功能相关贡献。此外，MRGO 的比电容揭示了涉及 MnO ₂中的 Mn(III)/Mn(IV) 氧化还原反应的氧化还原过程的赝电容贡献。这项工作利用电化学和非原位XAS 技术来阐明超级电容器应用的电荷存储机制。