Bifunctional Pt–SnOx nanorods for enhanced oxygen reduction and hydrogen evolution reactions

Abstract

The composition and configuration are the deciding factors for catalytic properties and are constrained by the physical nature of the selected elements, thereby influencing the functionality of heterogeneous catalysts. In view of this, herein, a one-dimensional bifunctional heterogeneous nanocatalyst consisting of SnO₂ capped Pt nanorods (Pt–SnO_x NRs) is developed via the formic acid reduction method (FAM), showing high oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) performance. The performance of the as-prepared Pt–SnO_x NRs was 1.4-fold higher than that of the commercial J.M.-Pt/C catalyst with an outstanding mass activity (MA) of 160 mA mg_Pt⁻¹ at 0.85 V vs. SHE towards the ORR in acidic medium. Of special relevance, these Pt–SnO_x NRs exhibit notable stability and retained 87% of their initial MA when operated up to 5k cycles in an accelerated durability test (ADT) in the ORR. Moreover, the Pt–SnO_x NRs achieved a remarkably lower overpotential (η) of 48 mV (at a current density of 10 mA cm⁻²) and a Tafel slope of 33 mV dec ⁻¹ in the HER, significantly lower than those of the commercial J.M.-Pt/C catalyst (η = 60 mV and Tafel slope = 38 mV dec⁻¹). Besides, such a material maintained its 100% HER activity in a chronoamperometric (CA) stability test up to 6 h. By cross-referencing the results of structural and electrochemical inspections, such a high bifunctional performance of Pt–SnO_x NRs is attributed to the synergistic collaboration between the SnO₂ modifier and Pt atoms. The SnO₂ accelerates the HO–H bond cleavage during the HER and simultaneously promotes the desorption of oxygen species on the Pt surface in the ORR, which later triggers the reduction reaction performance. Meanwhile, SnO₂ provides a shielding effect to Pt under harsh reduction conditions and thus high stability of Pt–SnO_x NRs is achieved.