Synergistic Cr-doping and crystalline/amorphous heterointerface engineering to promote surface reconstruction of FeCo LDH for efficient oxygen evolution

Abstract

The development of highly efficient electrocatalysts for the oxygen evolution reaction (OER) is crucial for advancing hydrogen production technologies. In this study, we employed a dual strategy involving Cr-doping and the construction of an amorphous NiS_x heterointerface to significantly boost the OER activity of FeCo layered double hydroxides (LDHs). The amorphous NiS_x, with its long-range disordered structure and abundant unsaturated coordination sites, together with Cr doping, promotes electron transfer kinetics and thus facilitates the dynamic reconstruction of FeCo LDH into highly active FeCoOOH, as evidenced by in situ Raman spectroscopy and operando electrochemical impedance spectroscopy. DFT calculations further reveal that both Cr-doping and the crystalline/amorphous heterointerface modulate the d-band centers of Fe/Co atoms, lower the energy barrier for the transformation of oxygenated intermediates, and synergistically optimize the adsorption/desorption behavior of reaction species, promoting rapid FeCo LDH restructuring, enhancing oxygen evolution kinetics, and thereby enhancing OER kinetics. As a result, the Cr-FeCo LDH/NiS_x catalyst delivers outstanding OER performance in 1 M KOH, requiring ultralow overpotentials of only 167 and 240 mV to achieve 10 and 100 mA cm⁻² respectively. Moreover, it demonstrates remarkable stability, maintaining continuous operation for 100 h at 100 mA cm⁻² in both simulated seawater (1 M KOH + 0.5 M NaCl) and natural seawater alkaline electrolytes (1 M KOH + seawater).