Atomic Pt-Promoted Hierarchical CoP@CNTs-Bridged CeO₂–CoP Heterostructure-Based Hollow Microcubes for Water Electrolysis

In this work, the electrocatalyst systems of CoP nanoparticles confined within carbon nanotubes are presented, which bridge CeO₂–CoP heterostructures embedded in nitrogen-doped hollow carbon nanocubes (CoP@CNTs/CeO₂–CoP@NCs) and further engineered with Pt single atom (Pt–CoP@CNTs/CeO₂–CoP@NCs). The Pt–CoP@CNTs/CeO₂–CoP@NCs catalyst exhibits outstanding performance for hydrogen and oxygen evolution in 1.0 m KOH medium. The two-electrode Pt–CoP@CNTs/CeO₂–CoP@NCs₍₋₎||CoP@CNTs/CeO₂–CoP@NCs₍₊₎ configuration reaches a low cell voltage of 1.52 V in 30 wt.% KOH and 1.53 V in 1.0 m KOH. This system further demonstrates exceptionally high mass activity, ≈38.5-fold greater than that of commercial Pt/C₍₋₎||RuO₂₍₊₎. The fabricated anion exchange membrane electrolyzer stack provides a stack voltage of 1.71/1.84/2.04 V at 0.5/1/2 A cm⁻² in 1.0 m KOH at 60 °C and excellent stability for over 1400 h. The CeO₂–CoP heterostructures-sealed nitrogen-doped hollow carbon nanocubes-bridged CoP@CNTs architecture owns a hierarchical structure with numerous metallic heterogeneous interfaces and efficient connection between different active phases to ensure abundant active sites, superb conductivity, short electron transfer pathways, and controlled adsorption/desorption of intermediates for rapid OER kinetics. In addition, the incorporation of a small Pt amount into CoP@CNTs/CeO₂–CoP@NCs generates unique electronic properties to reach high catalytic HER performance, thereby yielding the efficient electrocatalyst systems for sustainable and economically viable water splitting.