Ni/Co doped 1T/2H MoS 2 as a robust bifunctional electrocatalyst for hydrogen and oxygen evolution in both acidic and alkaline media

Abstract

The metastable 1T-phase of molybdenum disulfide (MoS¬¬¬2) exhibits remarkable electrical conductivity and enriched electrochemically active sites, rendering it a promising electrocatalyst for the hydrogen evolution reaction (HER). However, its instability and poor oxygen evolution reaction (OER) performance hinder its effectiveness as a bifunctional catalyst. To address these limitations, this work presents Ni/Co co-doped 1T/2H MoS2 catalyst (CN-MDS) synthesised via a facile hydrothermal approach, achieving remarkable HER and OER activity in both acidic and alkaline environments. The strategic incorporation of Ni and Co stabilises the 1T phase and tailors the electronic structure, significantly enhancing the overall electrocatalytic performance. The optimised CN-MDS catalyst exhibits outstanding electrochemical activity, delivering reduced overpotentials of 84/91 mV (HER) and 232/240 mV (OER) at 10 mA cm-2, with Tafel slopes of 42/48 mV/dec and 55/57 mV/dec in acidic/alkaline environments, respectively. In a two-electrode set-up, CN-MDS enables efficient bifunctional water splitting, achieving low cell voltages of 1.5/1.52 V at 10 mA cm-2 while retaining robust durability over 100 hours. Density functional theory (DFT) calculations further confirmed that the CN-MDS NPs serve as active catalysts for HER and OER. This work highlights the synergistic effect of bi-metal doping and phase engineering, offering a promising pathway for creating next-generation bifunctional electrocatalysts to enable sustainable energy solutions.