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 (similar to 300 degrees 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.

Automated summary

In this study, a scalable method for the preparation of carbon-supported Ru/RuO2 nano-boomerangs (Ru/RuO2NB/C) was reported. The carbon promotes the reduction of RuO2 to Ru at relatively low temperatures (about 300 degrees C) without other reductants. The synthesized Ru/RuO2NB/C exhibits excellent bifunctional catalytic activity and stability over the whole pH range, surpassing commercial RuO2/C in acidic, neutral, and alkaline aqueous solutions.