The Ni(OH)2@Fe-BDC@Fe3O4/NF composite catalyst with rich active interfaces and durable life for OER and overall water splitting

The composite electrocatalyst of Ni(OH)₂@Fe-BDC@ Fe 3 O 4 /NF was successfully prepared. • The Ni(OH)₂@Fe-BDC heterostructure and dispersed Fe 3 O 4 nanoparticles optimize electron transfer pathways. • It is outstanding catalyst with the overpotential of 149 mV at 10 mA·cm⁻². • It has durable OER life with nearly 100 h under initial 110 mA·cm −2 . • It possesses equally excellent HER and overall water splitting performance. Metal-organic frameworks (MOFs) have gradually become highly promising electrocatalytic materials applied in the reaction of oxygen evolution (OER), thanks to their extraordinarily high specific surface area, adjustable pore structure as well as ample redox active sites. However, their practical applications are hindered by intrinsically low electrical conductivity and inadequate cycling stability. The present research introduces a brand-new Ni(OH) 2 @Fe-BDC@Fe 3 O 4 /NF nanocomposite electrocatalyst that was successfully prepared via a stepwise solvothermal method on a Ni foam (NF) support. Systematic structural characterizations confirmed that Ni(OH) 2 nanosheets in the composite exists as a mixture structure of honeycomb-like and flower-cluster-like, which uniformly anchored at the surface of Fe-BDC@Fe 3 O 4 /NF. Moreover, the coexistence of Ni(OH) 2 , Fe-BDC and Fe 3 O 4 three phases was verified in the composite. And Fe 3 O 4 nanoparticles are evenly dispersed in Fe-BDC crystal nanolayers. Electrochemical tests in 1 mol/L KOH alkaline electrolyte demonstrated that the Ni(OH) 2 @Fe-BDC@Fe 3 O 4 /NF composite exhibited superior OER catalytic activity and complete hydrolysis performance compared with the single-component Ni(OH) 2 /NF and Fe-BDC@Fe 3 O 4 /NF, delivering an overpotential as low as 149 mV under a current density of 10 mA·cm −2 , alongside a full water decomposition voltage of 1.53 V at 50 mA·cm −2 . The improved performance stemmed from the strong interfacial electronic interaction between Ni(OH) 2 and Fe-BDC@Fe 3 O 4 , which induced a negative shift in the binding energies of Ni 2p and Fe 2p, increased the interfacial charge density, reduced the charge transfer resistance (Rct = 0.8 Ω) and enlarged the electrochemical specific surface area (ECSA). In addition, the composite showed excellent long-term durability, with only 8.30% activity decay following 100 h of non-stop chronoamperometry testing under initial current density of about 110 mA·cm −2 . Structural evolution analysis after the stability test revealed that the Fe 3 O 4 phase underwent reductive decomposition and in-situ reconstruction with Ni(OH) 2 to form amorphous Ni- Fe oxyhydroxide, which served as the real active sites. This research offers a feasible approach for the structural design of iron-based MOF composite electrocatalysts, deepens the understanding of the role of interfacial synergetic mechanism between metal hydroxides and MOFs in improving OER performance, and offers experimental evidence for the advancement of high-performance non-noble metal electrocatalysts applied in water electrolysis. Download: Download high-res image (202KB) Download: Download full-size image