Janus Ru/RuO2 nano-boomerangs on carbon as pH-universal electrocatalysts with bifunctional activity toward the hydrogen/oxygen evolution reaction

Efficient pH-universal overall water-splitting electrocatalysts are critical for reducing energy consumption and simplifying cell design; however, challenges remain. In this study, we report a scalable method for the preparation of new carbon-supported Ru/RuO2 nano-boomerangs (Ru/RuO2NB/C). The Ru/RuO2NB with a novel Janus nanostructure exposes both Ru and RuO2 active sites independently on the two arms of the nano-boomerangs without inhibiting their activities. Herein, for the first time, it is demonstrated that carbon promotes the reduction of RuO2 to Ru at relatively low temperatures (∼300 °C) without any other reductants. A new facile process was developed for the preparation of well-dispersed RuO2 nanorods on carbon supports (RuO2NR/C), which were then converted to a Ru/RuO2NB Janus nanostructure. The synthesized Ru/RuO2NB/C exhibits excellent bifunctional catalytic activity and robust stability toward the hydrogen/oxygen evolution reaction (HER/OER) in an aqueous solution over the whole pH range. The OER/HER metal mass activity (jm)/turnover frequency (TOF) of Ru/RuO2NB/C is five times higher than that of commercial RuO2/C in acidic, neutral, or alkaline aqueous solutions. In a wide pH range, the TOF and jm of Ru/RuO2NB/C are higher than those of most OER and HER electrocatalysts. The HER activity of Ru/RuO2NB/C surpassed that of Pt/C in an alkaline solution. The tannic acid (TA) fragment from TA modification of carbon produces the high thermal stability of Ru/RuO2NB/C catalysts.