Facile electrochemical phosphatization of Mn₃O₄ nanosheet arrays for supercapacitor with enhanced performance

Phosphating manganese oxide (PMn) nanosheet arrays were synthesized via a facile and fast cathodic electrodeposition and following cyclic voltammetry phosphating as binder-free electrode materials for supercapacitors application. The morphology, chemical composite and structure characteristic of PMn nanosheets confirm that phosphate ions have been introduced to the surface of Mn₃O₄ nanosheets successfully. The as-prepared PMn electrode shows excellent electrochemical properties in 0.1 M Na₂SO₄ aqueous solution with a three-electrode system. The optimal specific capacitance of the PMn nanosheet arrays electrode at 5 mV s⁻¹ (6.7 mF cm⁻²) is superior to that of the Mn₃O₄ nanosheets electrode (2.7 mF cm⁻²). Furthermore, the specific capacitance of obtained PMn nanosheets electrode reaches a retention of 87.6% after 5000 charge–discharge cycles at 0.08 mA cm⁻², indicating great cycling stability. Therefore, modification of phosphate ions can effectively suppress the dissolution of manganese oxide and achieve a significant improvement in electrochemical property for supercapacitors with a manganese oxide electrode.