Er-intercalated Ti ₃ C ₂ T _<i>x</i> MXene electrocatalyst for efficient energy conversion

For sustainable green hydrogen production, bifunctional catalysts must rival or surpass precious metal electrocatalysts in water splitting. MXenes, with their rich surface chemistry, unique physicochemical properties, and stability, have emerged as promising candidates. However, achieving balanced hydrogen evolution (HER) and oxygen evolution (OER) activity in a single medium remains challenging. Herein, we report the synthesis of Ti₃C₂T _<i>x</i> MXene and erbium intercalated (Er@Ti₃C₂T _<i>x</i> ) nanocomposites as bifunctional electrocatalysts for overall water splitting in alkaline media. The Er@Ti₃C₂T _<i>x</i> catalyst demonstrates outstanding HER performance, requiring only 256 mV overpotential at 10 mA cm^-2 with a Tafel slope of 102 mV dec^-1, while also exhibiting superior OER activity with an overpotential of 381 mV at 10 mA cm^-2 and a Tafel slope of 157 mV dec^-1. Electrochemical tests were conducted in 1 M KOH using an Ag/AgCl reference electrode and a Pt wire as the counter electrode. Chronoamperometry confirmed long-term stability and durability. Structural and morphological analyses conducted using XRD, SEM, EDX, FTIR, and Raman spectroscopy verified the successful intercalation of Er while preserving the 2D MXene structure. A notable increase in <i>d</i>-spacing from 8.9 Å (pristine MXene) to 12.2 Å (Er@Ti₃C₂T _<i>x</i> ) further confirmed erbium (Er) incorporation. Moreover, electrochemical impedance spectroscopy (EIS) revealed reduced charge-transfer resistance, highlighting enhanced kinetics and efficiency for water-splitting reactions.