Ordered layer induced by polydopamine enabling MXene electrodes with high areal capacitance

The surfaces of MXene etched via chemical etching feature randomly diverse terminals, which creates an uneven surface potential. The non-uniform potential promotes disordered stacking of nanosheets, which in turn precipitates a rapid deterioration in the electrochemical performance of MXene-based electrodes at high mass loadings (ML). In this study, L-ascorbic acid (AA) is used to block polymerization of dopamine (DA), forming a uniform polydopamine (PDA) coating on MXene surfaces, which corrects the surface potential distribution. And we add borax to do a further modification to increase stabilization. Characterization results demonstrate that introducing AA creates a more uniform PDA coating and surface potential distribution, which not only increases the interlayer spacing but also improves the in-plane stacking orderliness of the nanosheets, which is beneficial for electrolyte transport. The as-prepared electrode retains high areal capacitance (5.6 F cm −2 ) at 10.0 mg cm −2 , and the resulting symmetric device exhibits outstanding cycling stability. This study offers an insight for optimizing the surface potential and orientation of MXene, paving the way toward high ML electrode applications.