Improvement in Oxygen Evolution Performance of NiFe Layered Double Hydroxide Grown in the Presence of 1T-Rich MoS₂

Abstract

NiFe layered double hydroxide (NiFe LDH) grown in the presence of MoS₂ (rich in 1T phase) shows exceptional performance metrics for alkaline oxygen evolution reaction (OER) in this class of composites. The as-prepared NiFe LDH/MoS₂ composite (abbreviated as MNF) exhibits a low overpotential (η₁₀) of 190 mV; a low Tafel slope of 31 mV dec^-1; and more importantly, a high stability in its performance manifested by the delivery of current output for 45 h. It is important to note that this could be achieved with an exceedingly low loading of 0.14 mg cm^-2. The mass activity of this composite (97 A g^-1) is about 14 times greater than that of the conventional RuO₂ (7 A g^-1) at (η = 200 mV. When normalized with respect to the total metal content, a mass activity of 1000 A g^-1 (η = 300 mV) was achieved. Impedance analysis further reveals that the significant reduction in charge-transfer resistance and hence high current density (5 times greater as compared to NiFe LDH at η = 300 mV) observed for MNF is associated with interfacial adsorption kinetics of intermediates (R₁). Significant enhancement in the intrinsic activity of MNF over LDH has been observed through normalization of current with the electrochemically active surface area. Computational studies suggest that the Ni centers in the composite act as the active sites for OER, which is well-corroborated with the observed postreaction appearance of Ni³⁺ species.