Intentional Replacement Acceleration Layer Strategy Achieves Superior Water/Seawater Electrolysis at Industrial‐Level Current Densities

Abstract Developing efficient electrocatalysts suitable for industrial water electrolysis and direct seawater electrolysis contributes significantly to the large‐scale advancement of the green hydrogen industry. Ru‐based catalysts hold great application prospect due to the optimized electronic structures, but the potential impact of replacement reactions between Ru ions and transition metal substrates during the synthesis process is often overlooked. In this study, the possible effects of replacement reactions between different transition metal substrates and noble metal ions on the electrode performance are systematically investigated. Furthermore, an intentional “replacement acceleration layer” strategy is proposed basing on the unintentional replacement reactions, achieving the ultrafast synthesis of high‐performance Ru‐based multiphase nanoparticles (Ru‐FeNiO x H y /NF). The hydrogen evolution reaction overpotential of Ru‐FeNiO x H y /NF at a high current density of 1000 mA cm −2 in alkaline electrolyte is only 196 mV, and it exhibits more than 100 h of long‐term stability at a current density of 500 mA cm −2 . Combined with the easily scalable synthesis approach, Ru‐FeNiO x H y /NF holds great potential for industrial applications. The combination of experimental and theoretical results confirms that the metallic Ru, hydroxide components, and RuO x in the composition synergistically endow Ru‐FeNiO x H y /NF with excellent HER activity.