Strong metal–support interaction in copper hexacyanoferrate nanocube decorated functionalized multiwall carbon nanotubes for enhanced bi-functional oxygen electrocatalytic activity and stability

Abstract

The development of an efficient non-precious metal-based bi-functional oxygen electro-catalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is crucial for various electrochemical energy conversion and storage devices. Prussian blue and its analogues (PBAs) have attracted attention as potential electrocatalyst materials due to their suitable properties including abundant metal centres, a porous 3D framework, a tuneable morphology, ease of synthesis and cost effectiveness. However, poor conductivity and low chemical stability under harsh conditions hinder their practical application as their activity is lower than that of commercial Pt/C catalysts. To address these limitations, we have developed 1D/3D hybrid nano-heterostructures of copper hexacyanoferrate (CuHCF) decorated functionalized multi-walled carbon nanotubes (f-MWCNTs) by a simple hydrothermal approach. The crafted electrocatalyst exhibits enhanced ORR and OER activity compared to its parent materials. The improved performance is assigned to the synergistic effect between CuHCF and f-MWCNTs, where the catalytic centre of Cu assists the adsorption and mass diffusion of oxygen species, and the interlinked structure of 3D CuHCF with 1D f-MWCNTs helps in effective electron transport to the catalytic centres. It was observed that the formation of a Cu(OH)₂ thin layer on the surface of CuHCF is also a main factor for enhanced electrocatalytic activity. To support the claims, activity comparison with CuHCF/unf. CNT (unfunctionalized CNTs) and Cu(OH)₂/CNT is performed. This work provides a new insight towards improving the efficiency of non-precious CuHCF based metal–organic framework electrocatalysts for oxygen electrocatalysis, an important class of reactions in fuel cell applications.