Systematic Tuning of Lattice Strain and Surface Structures of Platinum Alloy Nanowires for Enhanced Oxygen Reduction Performance

Abstract

The development of nanostructured catalysts with improved oxygen reduction reaction (ORR) performance is pivotal for advancing high-performing polymer electrolyte fuel cells (PEFCs). In this study, we synthesized Pt-alloy nanowires with systematically tuned morphologies, ranging from smooth structures to nanobumpy architectures, and investigated their impact on ORR performance. By investigating synthesis parameters, a nanobumpy Pt70Ni28Co1W1 nanowire supported on carbon delivered high ORR performance: mass activity of 1.6 A mgPt−1 and specific activity of 3.9 mA cmPt−2, which are approximately 6 and 11 times higher, respectively, than those of the commercial Pt nanoparticle catalyst on carbon. Structural characterization shows that alloying combined with nanobumpiness substantially increases compressive lattice strain (≈−3% for nanobumpy Pt-alloy nanowires versus ≈−1% for smooth Pt-alloy nanowires). Most of the developed catalysts exhibited improved specific ORR activity with increasing compressive lattice strain; however, a nanowire exhibited low ORR-specific activity, despite possessing a strong compressive strain of (≈−3%). Surface analysis indicates that achieving enhanced catalytic activity requires both pronounced compressive strain and an increased exposure of highly active surface facets, such as (111) facets and high-index step sites. These structure-controlled Pt-alloy nanowires, along with the described synthesis strategies, provide valuable insights into the structural design of advanced ORR electrocatalysts.