4D printing of MXene hydrogels for high-efficiency pseudocapacitive energy storage

Abstract

Abstract2D material hydrogels have recently sparked tremendous interest owing to their potential in diverse applications. However, research on the emerging 2D MXene hydrogels is still in its infancy. Herein, we show a universal 4D printing technology for manufacturing MXene hydrogels with customizable geometries, which suits a family of MXenes such as Nb2CTx, Ti3C2Tx, and Mo2Ti2C3Tx. The obtained MXene hydrogels offer 3D porous architectures, large specific surface areas, high electrical conductivities, and satisfying mechanical properties. Consequently, ultrahigh capacitance (3.32 F cm−2 (10 mV s−1) and 233 F g−1 (10 V s−1)) and mass loading/thickness-independent rate capabilities are achieved. The further 4D-printed Ti3C2Tx hydrogel micro-supercapacitors showcase great low-temperature tolerance (down to –20 °C) and deliver high energy and power densities up to 93 μWh cm−2 and 7 mW cm−2, respectively, surpassing most state-of-the-art devices. This work brings new insights into MXene hydrogel manufacturing and expands the range of their potential applications.

Production of Polymer Hydrogel Composites and Their Applications

“…To date, a number of MXene hydrogels have been created through the use of filtration, metal ions, graphene oxide, or polymers as crosslinkers, such as polyvinyl alcohol (PVA), polyacrylamide, cellulose, chitosan, poly(acrylic acid), and poly(N-isopropylacrylamide), with some success. Despite this, MXene hydrogel research is still in its infancy and faces significant obstacles [107].…”

Monolithically integrated flexible sensing systems with multi-dimensional printable MXene electrodes

“…The high modulus and yield stress represent stiffness characteristics, which are ideal for the fine printing precision and construction of stable, free-standing structures. 18 These rheological results indicate that the MXene–BPEI nanocomposite gel has a high viscosity, desirable shear thinning properties, and rapid viscosity recovery for practical use in extrusion-based 3D printing. The viscosity and rheological properties of the screen printable inks (with an MXene concentration of 20 mg mL −1 ) were also investigated (Fig.…”

“…This shear thinning behavior is desirable for 3D printing because it allows continuous extrusion in the printing process. 18 The gel ink viscosity also gradually increased as the amount of BPEI increased (Fig. 2e and S3a, ESI †).…”

“…17 MXenes, a class of two-dimensional layered transition metal carbides or nitrides, have leaped to the forefront as a suitable electrode material for printed electronics. 18 The most widely studied MXene, Ti 3 C 2 T x , has unique electrochemical, electrical, optical, and mechanical properties, including metallic conductivity, hydrophilicity, and large energy storage capacity. 19 Ti 3 C 2 T x also shows solution processability and thixotropy, which allows the controllable formation of stable additive-free aqueous colloidal dispersions without additives and makes itself well-suitable for printable microelectronic devices.…”

Asymmetrically Coordinated Cu–N1C2 Single‐Atom Catalyst Immobilized on Ti3C2Tx MXene as Separator Coating for Lithium–Sulfur Batteries

“…the excellent conductivity and layered microstructure, MXenes have attracted much attention in assembling energy storage and conversion devices. [36][37][38][39] Among various MXenes, the representative Ti 3 C 2 T x exhibits well potential when applied in the modified separator for Li-S batteries, [40,41] which is also ascribed to the strong chemical interaction between LiPSs and Ti 3 C 2 T x with polar surface, and its metallic conductivity. [42][43][44] Particularly, Ti 3 C 2 T x with abundant titanium vacancies could be just ideal support to stabilize and modulate isolated metal atoms.…”