Transition metal phosphides (TMPs) show promise as low-cost (pre)electrocatalysts for water splitting and other energy-related applications. However, their traditional synthesis methods face challenges in energy consumption, stability, and reproducibility due to the reaction at high temperatures. Here, the Joule heating (JH) method for the scalable synthesis of TMPs (Ni, Cu, and In) as self-standing electrodes and powders is presented. The JH synthesis demonstrates substantial economic efficiency and significantly reduces energy consumption and environmental impacts while enhancing reproducibility due to fast processing times. Large-scale nickel phosphide-based electrodes are synthesized with various transition metal dopants and assembled into an anion exchange membrane water electrolyzer as anode and cathode, maintaining a cell potential of a maximum of 1.8 V at 200 mA cm⁻² under 55 °C for 7 days. These results highlight the JH synthesis as a promising approach for the scalable production of high-performance self-standing electrodes for energy-related devices.