This study presents a rapid Joule heating method to synthesize RuMo alloy-based electrocatalysts on MoOx supports, aiming to improve the electrocatalytic activity and stability for ampere-level hydrogen evolution. The as-prepared RuMo@MoOx-JH catalyst exhibits excellent stability (2000 h at 1000 mA cm\(^{-2}\)) and low overpotentials (9 mV, 18 mV, and 15 mV in 1M KOH, 1M PBS, and 0.5M H\(_2\)SO\(_4\) solutions, respectively). First-principle simulations and operando measurements reveal the enhanced electrocatalytic performance and stability. The rapid Joule heating method is highlighted for its role in achieving highly efficient alloy-based electrocatalysts. The RuMo@MoOx-JH catalyst demonstrates competitive cost-effectiveness for industrial applications, with an energy consumption of 3.82 kW h m\(^{-2}\) and an electricity-to-hydrogen conversion efficiency of 89.2% at 60 °C.This study presents a rapid Joule heating method to synthesize RuMo alloy-based electrocatalysts on MoOx supports, aiming to improve the electrocatalytic activity and stability for ampere-level hydrogen evolution. The as-prepared RuMo@MoOx-JH catalyst exhibits excellent stability (2000 h at 1000 mA cm\(^{-2}\)) and low overpotentials (9 mV, 18 mV, and 15 mV in 1M KOH, 1M PBS, and 0.5M H\(_2\)SO\(_4\) solutions, respectively). First-principle simulations and operando measurements reveal the enhanced electrocatalytic performance and stability. The rapid Joule heating method is highlighted for its role in achieving highly efficient alloy-based electrocatalysts. The RuMo@MoOx-JH catalyst demonstrates competitive cost-effectiveness for industrial applications, with an energy consumption of 3.82 kW h m\(^{-2}\) and an electricity-to-hydrogen conversion efficiency of 89.2% at 60 °C.