A review on the synthesis methods and environmental applications of MAX phase and MXenes

Abstract

MXenes, a novel class of two-dimensional transition metal carbides and nitrides, have garnered significant attention due to their exceptional physicochemical properties, including high electrical conductivity, tunable surface chemistry, and hydrophilicity. These features make them highly promising for environmental and energy-related applications. This review presents a comprehensive analysis of MXenes’ structural, electrical, and magnetic characteristics, along with a critical evaluation of their synthesis strategies such as etching, top-down, and bottom-up approaches, each offering distinct advantages and limitations. In environmental remediation, MXenes demonstrate adsorption capacities up to 3–5 times greater than conventional materials such as activated carbon, graphene oxide, and zeolites, enabling rapid and efficient removal of heavy metal ions and organic pollutants. Their integration into membrane systems significantly reduces fouling and facilitates electrochemical regeneration, addressing key limitations in traditional wastewater treatment technologies. In energy applications, MXenes exhibit outstanding performance in electrocatalytic processes, including hydrogen evolution (HER), oxygen evolution (OER), and oxygen reduction reactions (ORR), as well as in photocatalysis and catalytic degradation. As energy storage materials, they offer high capacity and fast charge–discharge rates, particularly in lithium-ion batteries. This review also addresses major challenges, including oxidation, layer restacking, and limited scalability, while highlighting emerging solutions such as HF-free synthesis, surface functionalization, and hybrid material design. Furthermore, the integration of polymers like PVA, PEO, and PEDOT significantly enhances MXene properties, including electrical conductivity, mechanical strength, and ion transport. This paper presents a detailed overview of MXenes' promise, limitations, and recent advances in environmental and energy-focused applications.