Lattice-matched spinel/layered double hydroxide 2D/2D heterojunction towards large-current-density overall water splitting

It is fascinating and challenging to construct earth-abundant first-row transition metal-based bifunctional electrocatalysts for large-scale hydrogen production via water electrolysis. Here we report a progressive conversion from spinel nanosheets to layered double hydroxide (LDH) nanosheets through the preferential dissolution of alternated layers in spinel. This process enables the formation of a lattice-matched and chemically bonded edge-to-edge spinel/LDH 2D/2D heterojunction. Significant charge redistribution at the 2D/2D heterointerface accelerates water dissociation kinetics and optimize adsorption energy of hydrogen- and oxygen-containing intermediates. The synthesized CoFe2O4/CoFe-LDH 2D/2D heterojunction demonstrates exceptional performance in the hydrogen evolution reaction, achieving an overpotential of 337 mV at a high current density of 1000 mA cm-2, surpassing previously reported non-noble metal-based spinels and LDHs. Furthermore, its oxygen evolution reaction performance is comparable to that of typical spinel and LDH catalysts. The in-depth insights can guide rational interfacial engineering of heterogeneous catalysts for energy and environmental applications.