In-situ construction of Ru/RuO2 composites integrated on carbon nitride for highly efficient acidic oxygen evolution reaction

The design of efficient, durable and low-loading noble metal electrocatalysts for acidic oxygen evolution reaction (OER) remains highly desirable and is paramount for scalable hydrogen production in proton exchange membrane water electrolyzer (PEMWE). In this work, Ru/RuO 2 composite catalysts anchored on graphitic carbon nitride (g-C 3 N 4 ) are prepared via a simple hydrothermal–calcination synthetic route. The simultaneous partial reduction of RuO 2 by g-C 3 N 4 in calcination process results in the in-situ construction of Ru/RuO 2 heterojunctions. The optimized Ru/RuO 2 /g-C 3 N 4 -2 catalyst exhibits robust catalytic activity toward the acidic OER superior to pristine RuO 2 with an overpotential of 179.5 mV to achieve 10 mA cm −2 , a Tafel slope of 60.72 mV dec −1 and exceptional durability for 100 h without noticeable degradation. More importantly, Ru/RuO 2 /g-C 3 N 4 -2 catalyst has a low Ru loading of 0.125 mg cm −2 and exhibits a robust mass activity of 293.84 mA mg-1 Ru, which is 21 times greater than that of benchmark RuO 2 . This work highlights a viable strategy toward engineering high-performance, low-noble-metal-loading catalysts for acidic oxygen evolution, and provides a rational and scalable approach for constructing ultra-low–loading RuO 2 -based acidic OER catalysts through electronic modulation and interfacial engineering. • Ru/RuO 2 composites composed of metallic Ru and crystalline RuO 2 are integrated on graphitic carbon nitride (g-C 3 N 4 ). • The optimized Ru/RuO 2 @g-C 3 N 4 -2 catalyst exhibits an overpotential of 179.5 mV to achieve 10 mA cm −2 for OER. • Ru/RuO 2 @g-C 3 N 4 -2 catalyst exhibits a robust mass activity of 293.84 mA mg Ru −1 .