Enriched asymmetric π electrons confining single-site Pt for acidic hydrogen evolution

Achieving both high activity and durability with minimal Pt loading is critical for acidic hydrogen evolution in large-scale proton exchange membrane water electrolyzers (PEMWEs), in which precise regulation of Pt-support interaction is the key yet remains a great challenge. Here, we report that by confining single-site Pt with enriched asymmetric π electrons on a monolayer graphene encapsulating CoNi nanoalloy, a highly active and durable Pt site is constructed, which delivers an unprecedented mass activity. Assembled PEMWE using this catalyst achieves a record-high current density of 4.0 A cm⁻² at 2.02 V with the lowest-ever-reported Pt loading of 1.2 μg_Pt cm⁻² and exhibits an excellent durability of 1,000 h at 2 A cm⁻². Comprehensive investigations reveal that CoNi-graphene 3d-2p orbital overlapping combined with CoNi-to-carbon electron transfer, perturbs the conjugation effect and orbital symmetry of graphene π electrons, leading to reinforced Pt–graphene bonding and electron enrichment on Pt, which enhances both catalytic stability and activity.