Phase-Engineered 1T–2H MoSe ₂ Anchored on Ti ₃ C ₂ T _x MXene as a Highly Efficient HER Catalyst

1T–2H MoSe 2 was grown in situ on Ti 3 C 2 T x MXene to develop a Pt-free HER electrocatalyst with enhanced interfacial charge transfer. The optimized composite delivers an overpotential of 68 mV at 10 mA cm –2 and a Tafel slope of 74 mV dec –1, along with excellent cycling stability of over 1000 cycles, showing negligible decay. The composite has an increased metallic 1T content and suppressed Mo 6+ surface oxides. Electrochemical measurements reveal a substantially reduced charge-transfer resistance ( R ct ∼ 31 Ω) and a large ECSA ( C dl = 22.6 mF cm –2 ). The catalyst showed improved activity, high TOF values, and a hydrogen-coverage profile consistent with a Volmer–Tafel pathway.