Ru-RuO2/CNT hybrids as high-activity pH-universal electrocatalysts for water splitting within 0.73 V in an asymmetric-electrolyte electrolyzer

Exploring high-activity electrocatalysts for water electrolysis is a pivotal field of hot research as hydrogen is a very promising renewable energy source and bountiful in supply. Understanding the structure–composition–property relationships is the key for engineering improved electrocatalysts. We herein report a rational design on Ru-RuO2 hybrid nanoparticles decorating carbon nanotubes composites electrocatalysts (Ru-RuO2/CNT), which shows impressively high activity toward hydrogen/oxygen evolution reaction (HER/OER) in all pH aqueous electrolytes. The Ru-RuO2/CNT, as an OER catalyst, requires ultralow overpotentials of 0.18 V, 0.27 V and 0.21 V to drive the current density of 10 mA cm−2 in acidic, neutral and alkaline media, respectively. Meanwhile, the catalyst also exhibits superior HER activity with the current density of 10 mA cm−2 at −0.063 V, −0.048 V and −0.012 V in acidic, neutral and alkaline media, respectively. Systematic characterizations and comprehensive electrochemical studies coupling with theoretical calculations verify that Ru favorably works with RuO2 and CNT to synergistically contribute such highly desirable electrocatalytic activity. The bifunctional catalytic properties, in conjunction with its pH-universal compatibility, inspire us to an asymmetric-electrolyte electrolyzer was set up, which can harvest the electrochemical neutralization energy with implementing electrolysis H2 generation with a current density of 10 mA cm−2 at an applied voltage of 0.73 V. The as-developed asymmetric-electrolyte electrolyzer, by coupling high-activity but not too expensive electrocatalysts with optimizing the catalytic efficiency in their favorable electrolyte, potentially provides an environmental-friend and energy-saving avenue for the future electrolysis H2 generation.