Core–shell CoPt@C assembled hierarchical catalysts via CH ₄ ‐deposition strategy for efficient overall water splitting

Abstract This study, a core–shell CoPt@C assembled hierarchical catalyst (named CoPt@C) was prepared using a unique CH 4 deposition strategy for highly efficient overall water splitting. CoPt@C is composed of dense CoPt@C core–shell nanoparticles (NPs) and a minor proportion of curled CoPt@nanotubes (CoPt@CNTs). Moreover, by adjusting the CH 4 deposition time, the carbon shell thickness can be effectively regulated. Benefiting from the synergistic interaction between CoPt alloy and carbon shell, coupled with the high conductivity of the carbon shell, the overpotential of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) for CoPt@C is 15 and 120 mV at 10 mA cm −2 . In addition, CoPt@C requires only 1.58 V to achieve 10 mA cm −2 for overall water splitting and maintains excellent stability over 80 h of continuous electrolysis. Density functional theory (DFT) calculations suggest that electrons transfer from the CoPt alloy NPs to the carbon shell, rendering the carbon shell electron‐rich. Additionally, the hydrogen adsorption energy (Δ G *H ) and the rate‐determining step (Δ G *OOH ) on CoPt@C are only −0.22 and 1.9 eV, respectively.