Self-Optimized Acidic Ceramic TiB₂ Electrocatalyst: In Situ Electrochemical Exfoliation for Enhanced Hydrogen Evolution.

TiB₂, a layered transition metal diboride with exceptional electronic conductivity and acid-resistant stability, has emerged as a promising electrocatalyst for acidic hydrogen evolution reactions (HER). However, its stacked crystalline architecture inherently limits active site availability and mass transport efficiency, necessitating high operating overpotentials. We report a spontaneously optimizing TiB₂ electrocatalyst through in situ electrochemical exfoliation during sustained HER operation in acidic media. Continuous potential-driven ion intercalation triggers structural exfoliation of bulk TiB₂ into lamellar nanosheets, simultaneously achieving-59% overpotential reduction (from 924 to 451 mV @10 mA cm⁻²) and a 10³-fold active site density increase. This self-optimization mechanism, revealed through characterization, originates from ion-induced interlayer electrostatic weakening and concomitant electronic structure modulation. Our findings establish an electrochemical activation strategy for layered borides, transitioning them from static precatalysts to dynamic active-phase systems.