The interaction of carbon nanotubes (CNTs) with CuCoO2 nanosheets promotes structural modification and enhances their OER performance

Abstract

In this study, carboxylated multi-walled carbon nanotubes (CNTs) were utilized to address the challenges of inherent conductivity mismatch of CuCoO₂ catalysts. CNT-supported CuCoO₂ nanosheets (CCO/xCNT, x = 25, 50, and 75) were successfully synthesized through a one-step hydrothermal method. The introduction of CNTs can reduce the thickness of CuCoO₂ to 25 nm due to the interaction between the CNTs and CuCoO₂, change the electronic structure, and increase the O–Co bond length and oxygen vacancy (V_O) concentration of CuCoO₂. These microstructure modifications significantly enhance the binding affinity between CuCoO₂ and OH⁻. The OER measurements of CCO/xCNT (x = 25, 50, and 75) electrocatalysts reveal that adding 50 wt% CNTs into the sample (CCO/50CNT) yields the best catalytic performance, which shows a low overpotential of only 343 mV at 10 mA cm⁻² and a small Tafel slope of 65 mV dec⁻¹. Additionally, CCO/50CNT also exhibits excellent structural and compositional stability. The density functional theory (DFT) calculations and pH dependence experiments show that the introduction of CNTs can generate V_O, which initiates lattice oxygen and facilitates both the Adsorption Evolution Mechanism (AEM) and the Lattice Oxygen Mechanism (LOM) on the catalyst surface during the OER process. A simple and general strategy is used to modify the catalyst microstructure and influence its OER mechanism, which helps to improve the OER performance of delafossite type metal oxides and even bimetallic oxides.