Exploring the Potential of MBenes Supercapacitors: Fluorine-Free Synthesized MoAl1–x B with Ultrahigh Conductivity and Open Space

The present study describes the synthesis of multilayered MBenes MoAl1-xB with different degrees of Al deintercalation using a mild, fluorine-free approach of dilute alkali to remove Al from MoAlB. We propose an etching route and compare it to conventional fluoride etching products. Additionally, the study explores the possible application and energy storage mechanism of MBenes in supercapacitors, marking the first investigation of its kind. At room temperature, 1/24-MoAl1-xB with terminal groups −OH exhibits ∼25% Al removal in 1 wt % NaOH for 24 h, outperforming traditional etching technology. Increasing the Al removal exposed more open space, resulting in a higher capacitance. Compared to LiF/HCl-MoAl1-xB (etched by LiF + HCl), 1/24-MoAl1-xB has a higher energy storage capability. The multilayered 1/24-MoAl1-xB film electrode exhibits ultrahigh conductivity with a rapid relaxation time of 0.97 s and high areal capacitance (2006.60 mF cm-2) while maintaining 80.2% capacitance after 5000 cycles. The MoAl1-xB all-solid-state supercapacitor (ASSS) delivers a high capacitance of 741.6 mF cm-2 at 1 mV s-1 for a single electrode and exhibits stable capacitance even at a 90° bending angle, highlighting its potential practical use. Our research represents an important step in the synthesis of MBenes and highlights their potential applications in supercapacitors.