MXene supported nickel-cobalt layered double hydroxide as efficient bifunctional electrocatalyst for hydrogen and oxygen evolution reactions

Abstract

An inexpensive and noble metal free electrocatalyst with high anion exchange capacity and intrinsic conductivity is highly desirable for renewable energy applications like hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). In this turn, low cost and earth abundant nickel cobalt hydroxides (NiCo(OH)2) based layered double hydroxides (LDHs) have been considered for a long time. However, aggregation of their flakes and structural instability lead to less accessible active sites and hence poor electrical conductivity which limit their electrocatalytic performance as an electrocatalyst. Therefore, MXene supported NiCo(OH)2 samples (with different ratios of Co) were prepared using one-step hydrothermal method possessing enlarged surface area and numerous active sites for enhanced electrochemical activity. As an electrocatalyst, MXene supported NiCo LDHs with 1:1.2 ratio (Ni:Co) (NCM-1.2) illustrated a convincing electrocatalytic activity for HER and OER as compared to NiCo(OH)2, MXene and other MXene supported samples. The improved electrocatalytic activity of NCM-1.2 can be attributed to active redox couples (Ni2+/3+ and Co2+/3+), improved accessible active sites (Ni2+ for HER and Co3+ for OER) and reduced interfacial charge transfer resistance.