Amplifying Intermetal Bias of Pt-Rh Alloy Nanolayers for Facilitated Hydrogen Inter-Diffusion and Evolution

Proton exchange membrane water electrolyzer driven by renewable electricity has been regarded as a sustainable energy production technology, but is greatly limited by the high cost and unsatisfactory durability of noble metal catalysts. Here, we present the proof-of-concept application of the amplified intermetal bias in PtRh alloy nanolayer to promote the intrinsic catalytic activity of hydrogen evolution reaction and the lifespan of the proton exchange membrane water electrolyzer. Both experimental and theoretical results revealed the key role of the intermetal bias between Pt and Rh amplified by the rectifying contact with nitrogen-doped carbons support in accelerating the pre-enrichment of protons on Rh sites, diffusion of H species from Rh to Pt sites, and final H dissociation from Pt sites. Consequently, the optimized Pt₃Rh₂/NC cathode with the most pronounced intermetal bias gives a record-high mass activity of 282 A mg_Pt+Rh ^-1 at a cell voltage of 1.8 V in proton exchange membrane water electrolyzer. Moreover, the Pt₃Rh₂/NC cathode can reduce the proton diffusion resistance from 0.95 Ω of Pt/C to 0.69 Ω at a cell voltage of 1.5 V due to the promoted hydrogen species diffusion on catalyst surface, largely decreasing the cell voltage and extending the lifespan by 3.2 times.