Investigating H2 Gas-Promoted Ir Deposition on Pt Black Nanoparticles for Synthesizing a Bifunctional Catalyst for OER and ORR in Acidic Media

Herein, we report the scalable synthesis of a bifunctional Pt@Ir core–shell electrocatalyst for the acidic oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Therefore, we deposit Ir on Pt black nanoparticles via a H₂ gas-promoted reduction of Ir³⁺ ions, exploiting the high activity of Pt toward H₂ oxidation. The affinity between Ir and Pt was proven in electrodeposition experiments, which supports the favored deposition of Ir on Pt and the delayed bulk deposition of Ir on Ir. This method yields a nanosized core–shell catalyst with an Ir content adjustable between 4 and 30 wt % Ir. Intuitively, an increased Ir content results in higher OER activity, while the ORR activity decreases. We show that the Pt core and the strong interaction between Pt and Ir affect the electrocatalytic behavior, since the ORR activity does not decrease to the same extent as the OER activity increases with progressive Ir deposition. The simplicity and robustness of this synthesis method are demonstrated by an upscaling of the synthesized catalyst amount by a factor of 10, revealing its great potential.