Enriched asymmetric π electrons in chainmail catalyst boost acidic hydrogen evolution

Proton exchange membrane (PEM) water electrolysis is an important technology to produce large-scale green hydrogen. Platinum on Carbon (Pt/C) is a state-of-the-art cathode catalyst due to its moderate hydrogen binding energy and high resistance to acid corrosion, however, its high Pt loadings significantly increase the costs.

In a study published in Joule, a research team led by Prof. DENG Dehui and Prof. YU Liang from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS), collaborating with Prof. LU Junling from the University of Science and Technology of China of CAS and Prof. YU Hongmei from the DICP, developed a highly efficient and stable catalyst for acidic hydrogen evolution. 

The researchers designed a chainmail catalyst consisting of a cobalt-nickel (CoNi) nano-alloy encapsulated in a monolayer of graphene, and discovered that electron transfer from CoNi to the carbon layer, along with 3d-2p electronic interaction, led to an enrichment of asymmetric π electronic states on the graphene surface. After depositing Pt single atoms using atomic layer deposition, these enriched asymmetric π electrons exhibited a unique confinement effect on the Pt atoms.

This confinement operated through two synergistic mechanisms. Electron transfer from CoNi to Pt via the graphene layer resulted in an electron-rich Pt site, optimizing hydrogen adsorption energy and promoting hydrogen desorption, thereby improving catalytic activity. Besides, strong interactions between the asymmetric π electrons and the Pt 5d orbital enhanced the structural stability of Pt sites, boosting the durability of the catalyst.

The researchers assembled a PEM water electrolyzer using this catalyst, which achieved an ultra-high current density of 4.0 A cm⁻² at 2.02 V and maintained excellent durability over 1,000 hours at 2 A cm⁻², using only 1.2 μg_Pt cm⁻² Pt loading. They also assembled a 2.85 kW PEM water electrolyzer using this catalyst, which operated stably for over 300 hours at an industrial current density of 1.5 A cm⁻², highlighting its outstanding industrial application potential.

"This work provides a new idea for developing high-performance, long-life and low-cost catalysts for hydrogen production via acid water electrolysis," said Prof. DENG.