Nanoporous Silicon with Graphene-like Coating for Pseudocapacitor Application

This paper presents the results of studies of the nanoporous silicon structure, both with different pore depths (up to 180 μm) and with layers in which a graphene-like coating was synthesized on the inner surface of the pores. The nanoporous layers were characterized by SEM as well as IR and Raman spectroscopy. Cyclic voltammetry and galvanostatic charge-discharge data in 3 M H₂SO₄ are presented as well as the results of the cyclic stability of these characteristics for the nanoporous structure. It was found that the degree of electrolyte pre-impregnation significantly affected the electrochemical processes, and the capacitance values depended on the depth (thickness) of the nanoporous layer. Increasing the thickness of the porous layer led to an increase in area-normalized pseudocapacity and was limited only by the mechanical strength of the structure. Performance improvement was also achieved by synthesis of the graphene-like layer in the volume of the nanoporous structure. The electrodes (composite materials) proposed in the work showed one of the best capacitive characteristics (87 mF/cm² with 100% capacity retention after 15,000 cycles) in comparison with the data reported in the literature at present.