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 Ti3C2Tx 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 Ti3C2Tx-AuNPs film thus demonstrated a rate performance that was preferable to that of pure Ti3C2Tx 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.

Keywords

• symmetric supercapacitors
• MXene
• chloroauric acid (HauCl₄)
• energy density
• power density
• aqueous electrolyte