Ordering Degree-Dependent Activity of Pt₃M (M = Fe, Mn) Intermetallic Nanoparticles for Electrocatalytic Methanol...

Atomically ordered intermetallic alloys with unique electronic and geometrical structures are highly attractive for heterogeneous catalysis and electrocatalysis. However, the formation of intermetallic phases generally requires high-temperature annealing to overcome the kinetic energy barrier of atom ordering, which unfortunately causes high material heterogeneity and thus makes it challenging to identify the exact contribution of ordered structures to the improved performance. Here, we prepared a family of small-sized intermetallic core/shell Pt₃M@Pt (M = Mn or Fe) catalysts with varied ordering degree by a high-temperature sulfur-confined method. We identified a strong correlation between the ordering degree of the intermetallic Pt₃M core of the catalysts and their electrocatalytic activity for the methanol oxidation reaction. Density functional theory calculations show that the intermetallic Pt₃M core induces a compressive strain on the Pt-skin, which weakens the CO* binding, lowers the free energy change from CO* to COOH*, and therefore promotes electrocatalytic methanol oxidation.