Constructing hierarchical arrays with core–shell metal oxides@metal coordination polymers for efficient and stable overall water splitting

Developing non-precious metal-based bifunctional electrocatalysts capable for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is essential to achieve efficient water electrolysis for mass hydrogen production, however it remains challenging. Here, we report the synthesis of hierarchical nanorod arrays comprising core–shell structured P-doped NiMoO₄@NiFe-coordination polymer (denoted as P-NiMoO₄@NiFeCP) as bifunctional electrocatalysts for water electrolysis. Furthermore, we systematically investigate the influence of NiFeCP shell thickness on electrocatalytic activity, manifesting the presence of strong interfacial synergetic effect between P-NiMoO₄ and NiFeCP for boosting both the HER and OER. With advantageous hierarchical architectures and unique core–shell structures, optimized P-NiMoO₄@NiFeCP-7.3 (7.3 is the shell thickness in nm) requires overpotentials of merely 256 and 297 mV to yield a current density of 1000 mA·cm⁻² for the HER and OER in 1 M KOH, respectively. More importantly, it can serve as a bifunctional electrocatalyst for efficient and sustainable overall water electrolysis, delivering large current densities of 500 and 1000 mA·cm⁻² at low cell voltages of 1.804 and 1.865 V, along with high stability of over 500 h at 1000 mA·cm⁻², demonstrating the great potential of this electrocatalyst towards practical applications.