1D α-NiMoO4 nanorods/reduced graphene oxide nanocomposite based efficient electrocatalyst for oxygen evolution reaction and p-nitrophenol sensing

In this work, nickel molybdate/reduced graphene oxide (α-NiMoO4/rGO) based bifunctional electrocatalysts for oxygen evolution reaction (OER) and p-nitrophenol (p-NP) sensing were studied. To replace noble metal-based catalysts for oxygen evolution reactions, it is essential to develop a potential alternative low-cost, electrochemically active catalyst. Even at a very low level p-NP present in water is harmful to the environment, so a rapid and sensitive method for detecting the presence of p-NP is indispensable. In this study, α-NiMoO4/rGO nanocomposite has been synthesized by hydrothermal method and used for OER and p-NP sensing. The XRD and Raman analysis confirm the α phase of NiMoO4 and SEM, and HRTEM studies confirm that 1D NiMoO4 growing on 2D rGO and the length and diameter of NiMoO4 rod are 5–10 μm and 50 nm, respectively. The α-NiMoO4 and α-NiMoO4/rGO showed an over-potential of 510 mV and 450 mV vs RHE, respectively for OER. The Tafel slope of the α-NiMoO4 and α-NiMoO4/rGO exhibited 159 mV dec−1 and 121 mV dec−1, respectively. The composite was found to split water into oxygen continuously for 23 h indicating its good stability for OER. For the electrochemical sensing of p-NP, the best OER performed α-NiMoO4/rGO-10 composite was chosen and modified with GCE. The sensor exhibits two sets of the linear range 0.5–10 μM and 30–500 μM for sensing of p-NP with a limit of detection 0.256 μM and sensitivity of 3.5042 μA cm2/μM. Cyclic voltammetry of α-NiMoO4/rGO/GCE differentiate different nitrophenol isomers.