Ultra-small carbon-supported FeRu alloy as a superior electrocatalyst for hydrogen evolution reaction

The development of highly efficient and low-cost electrocatalysts for hydrogen production through water splitting is extremely crucial and challenging. The introduction of transition metals to precious metals to form alloy electrocatalysts has been considered an effective strategy for regulating the electronic structure and catalytic properties. Moreover, particle size reduction is also a method for achieving effective electrocatalysts. In this study, we developed a simple two-step method for synthesizing ultra-small carbon-supported FeRu alloy nanoparticles. The bifunctional Fe0.05Ru0.05/XC-72 electrocatalyst with a diameter of 2.1 nm exhibited excellent activity and durability in alkaline fresh water and seawater electrolytes. The Fe0.05Ru0.05/XC-72 electrocatalyst required overpotentials of 13, 15, and 18 mV at a current density of 10 mA cm−2 in 1 mol L−1 KOH, 1 mol L−1 KOH + 0.5 mol L−1 NaCl, and 1 mol L−1 KOH + seawater, respectively. The Fe0.05Ru0.05/XC-72 electrocatalyst achieved a mass activity of 11.32 $${\rm{A}}\,{\rm{m}}{{\rm{g}}^{ - 1}}_{{\rm{noble}}\,\,{\rm{metal}}}$$ at −0.07 V vs. reversible hydrogen electrode in 1 mol L−1 KOH. Moreover, the Fe0.05Ru0.05/XC-72 electrocatalyst exhibited long-term hydrogen evolution reaction (HER) stability over 24 h in 1 mol L−1 KOH. Theoretical calculations indicate that the FeRu alloy could induce an electronic effect, leading to stronger *H adsorption ability and enhancing the HER performance. This study presents a promising approach for the future fabrication of excellent Ru-based electrocatalysts with high electroactivity and stability.