A bifunctional antioxidant for concurrent enhancement of stability and zinc-ion storage properties of Ti3C2Tx

Abstract

MXenes exhibit exceptional physicochemical properties, rendering them highly promising for applications in electrochemical energy storage devices. However, their easy oxidation and inherent tendency for self-stacking pose significant challenges, thereby limiting their utilization in practical applications. In this study, sodium sulfide (Na₂S) was used to enhance the stability of Ti₃C₂T_x under multiple environmental conditions. Additionally, compared to the reported antioxidants such as ascorbic acid (VC), sodium borohydride (NaBH₄), sodium ascorbate (NaAc), and sodium bisulfite (NaHSO₃), Na₂S possesses an appropriate level of reducing strength and was further used as the reducing agent to fabricate 3D macro-porous Ti₃C₂T_x/reduced graphene oxide (SMG) hydrogels at room temperature. This prevents the oxidation of Ti₃C₂T_x, which occurs during the traditional heated gelation process, and generates a porous structure conducive to ion transport. As a free-standing cathode for zinc-ion storage, the SMG electrode exhibits a high areal specific capacity of 526.2 mF cm⁻² at 2 mA cm⁻², much higher than that of the Ti₃C₂T_x/graphene oxide film (MG, 111.4 mF cm⁻²), together with outstanding cycling performance (83.6% capacity retention after 30 000 cycles). This study presents Na₂S as a bifunctional antioxidant for enhancing the stability of MXenes and constructing 3D MXene-based aerogels at room temperature with exceptional zinc storage performance.