2D/3D hierarchical and multi-heterostructured Co/Ni/Fe phosphosulfide as a highly efficient bifunctional electrocatalyst for overall water splitting

Morphological design and interfacial engineering are pivotal strategies for advancing electrocatalysis, however, achieving the optimization of both simultaneously remains a major challenge. To address this, we designed a multi-heterostructured bifunctional electrocatalyst cobalt-nickel-iron-phosphorus-sulfur composite (CoNiFe-PS) with a two-dimensional/three-dimensional (2D/3D) hierarchical structure, which was synthesized through simultaneous phosphating and sulfuration based on cobalt-nickel layered double hydroxide (CoNi-LDH) nano-sheets grafted with Prussian blue analogue (PBA) nanocubes. Notably, due to the distinctive morphology and synergistic effect between multi-heterostructure, the CoNiFe-PS catalyst demonstrated excellent performance in terms of ultralow overpotentials of 196 and 263 mV for oxygen evolution reaction (OER), as well as 63 and 235 mV for hydrogen evolution reaction (HER) at current densities of 10 and 100 mA cm-2. Moreover, the CoNiFe-PS|| CoNiFe-PS cell was constructed for overall water splitting in alkaline condition and exhibited minimal voltage requirements of 1.479 and 1.693 V to achieve 10 and 100 mA cm-2, respectively. This study provides a new perspective on fabricating multi-heterostructured bifunctional catalysts with unique morphology for highly efficient overall water splitting.