Bypassing the scaling relationship with spin selectivity: construction of Lewis base-functionalized heterostructural 2D nanosheets for enhanced oxygen evolution reaction

Abstract

Herein, Ni₃S₄-functionalized 2D CoFe-LDH heterostructure nanosheet was designed via the solvothermal method for oxygen evolution reaction (OER) in a wide pH range. The presence of negatively polarized sulfide ions over thiospinel significantly improvised the deprotonation of OH* intermediate in an exothermic pathway and allowed to bypass the scaling relation for OER. Moreover, as a result of improved magnetic ordering in active cobalt sites after heterostructure formation, Ni₃S₄@CoFe-LDH could accelerate the O₂ desorption in a spin-selective manner. Experimentally, Ni₃S₄@CoFe-LDH requires just 262 mV overpotential at 10 mA cm⁻² current density with a specific turnover frequency (TOF) value of 4.93 s⁻¹. Ni₃S₄@CoFe-LDH outperforms RuO₂, NiO, and other similar LDH or heterostructure materials not only in terms of overpotential value but also in terms of intrinsic TOF value, as a result of double bypassing in scaling relation. Density functional theory (DFT) calculations revealed that the synergy between interfaces on the Ni₃S₄@CoFe-LDH heterostructure can initiate the redistribution of electrons by charge transfer from CoFe-LDH to Ni₃S₄ and reduce the energy barrier of deprotonation of OH* and desorption of O₂ step, which significantly improve the intrinsic OER activity.