Fe(OH)_x modified ultra-small Ru nanoparticles for highly efficient hydrogen evolution reaction and its application in...

Developing highly active electrocatalysts for overall water splitting is of remarkable significance for industrial production of H₂. Herein, exceptionally active Fe(OH)_x modified ultra-small Ru nanoparticles on Ni(OH)₂ nanosheets array (Fe(OH)_x-Ru/Ni(OH)₂) for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are reported. The Fe(OH)_x-Ru/Ni(OH)₂ nanosheets array prepared with Fe/Ru molar ratio of 5 only requires extremely low overpotentials of 61, 127 and 170 mV to reach current densities of 100, 500 and 800 mA cm^-2 in 1 M KOH, respectively, exceeding Pt/C catalyst (75, 160 and 177 mV). Meanwhile, the Fe(OH)_x/Ni(OH)₂ nanosheets array derived from Fe(OH)_x-Ru/Ni(OH)₂ exhibits excellent OER activity. It gains current densities of 100, 500 and 800 mA cm^-2 at considerably low overpotentials of 265, 285 and 296 mV, respectively, much lower than those of RuO₂ and most reported electrocatalysts. The introduction of Fe(OH)_x significantly improves the HER activity of Ru nanoparticles by tunning the electronic structure and forming interfaces between Ru and Fe(OH)_x. Dramatically, the integrated alkaline electrolyzer based on Fe(OH)_x-Ru/Ni(OH)₂ and Fe(OH)_x/Ni(OH)₂ nanosheets array pair just needs 1.649 V to yield a current density up to 500 mA cm^-2, exceeding most reported water-splitting electrocatalysts. The strategy reported in this work can be facilely extended to prepare other similar Ru based materials and their derivatives with outstanding catalytic performance for water splitting.