The surface oxide reduction method is regarded as the optimal approach for determining the electrochemical active surface area of pure Pd. The present study methodically examines the applicability of this method to Pd–Co alloys. The findings reveal the adaptations that must be made when applying this method to Pd–Co alloys instead of pure Pd samples.

The surface oxide reduction method, a well-established technique for determining the electrochemically active surface area of Pd, is also widely used for Pd–Co alloys. However, comprehensive studies investigating the influence of the alloy composition on the determination of the surface area by the surface oxide reduction method are lacking for this alloy system. To fill this gap, a systematic investigation is conducted by applying the surface oxide reduction method to homogeneous Pd_100−x Co _x alloy samples with different compositions (x = 0−20). The results reveal that full monolayer coverage with surface oxide occurs at lower potentials than for pure Pd and that the surface area determined by this method systematically decreases with increasing Co content, indicating that only the Pd sites are accessible by this method. However, it is demonstrated that by taking the alloy composition into account, the surface area of the whole alloy can also be reliably determined.