Ultrahigh Energy and Power Densities of d-MXene-Based Symmetric Supercapacitors

Abstract

Here, rational design electrodes are fabricated by mixing MXene with an aqueous solution of chloroauric acid (HAuCl₄). In order to prevent MXene from self-restacking, the groups of -OH on the surface of Ti₃C₂T_x nanosheets underwent a one-step simultaneous self-reduction from AuCl₄-, generating spaces for rapid ion transit. Additionally, by using this procedure, MXene's surface oxidation can be decreased while preserving its physio-chemical properties. The interlayered MX/Au NPs that have been obtained are combined into a conducting network structure that offers more active electrochemical sites and improved mass transfer at the electrode-electrolyte interface, both of which promote quick electron transfer during electrochemical reactions and excellent structural durability. The Ti₃C₂T_x-AuNPs film thus demonstrated a rate performance that was preferable to that of pure Ti₃C₂T_x film. According to the results of the characterization, the AuNPs effectively adorn the MXene nanosheets. Due to the renowned pseudocapacitance charge storage mechanism, MXene-based electrode materials also work well as supercapacitors in sulfuric acid, which is why MXene AuNPs electrodes have been tested in 3 M and 1 M H₂SO₄. The symmetric supercapacitors made of MXene and AuNPs have shown exceptional specific capacitance of 696.67 Fg^-1 at 5 mVs^-1 in 3 M H₂SO₄ electrolyte, and they can sustain 90% of their original capacitance for 5000 cycles. The highest energy and power density of this device, which operates within a 1.2 V potential window, are 138.4 Wh kg^-1 and 2076 W kg^-1, respectively. These findings offer a productive method for creating high-performance metal oxide-based symmetric capacitors and a straightforward, workable approach for improving MXene-based electrode designs, which can be applied to other electro-chemical systems that are ion transport-restricted, such as metal ion batteries and catalysis.