Electrosynthesis/chemical in situ growth of the LDH/MOFs nanocomposite at the surface of carbon ceramic electrode for methanol oxidation reaction

Abstract

In this study, we developed a nanocomposite of Ni/Zn/Al-layered double hydroxide (LDH) and metal–organic frameworks (MOFs) through the electrochemical deposition of the Ni/Al LDH at the surface of the carbon ceramic electrode (CCE) and chemical in situ growth of Ni/Zn/Al LDH-MOF nanocomposite under mild conditions. The Ni/Zn/Al LDH-MOF nanocomposite modified CCE was analyzed using a range of instrumental methods. Then, the Ni/Zn/Al LDH-MOFs/CCE was employed for the electrocatalytic oxidation of methanol in alkaline solution. The Ni/Zn/Al LDH-MOFs/CCE shows enhanced electrocatalytic activity in 0.1 M sodium hydroxide toward the oxidation of methanol, with anodic peak current density proportional to methanol concentration. In continuation of electrochemical studies, the electron transfer coefficient (α) and the catalytic rate constant (k_cat) for the methanol oxidation reaction at the Ni/Zn/Al LDH-MOF/CCE were measured: α = 0.35 and k_cat = 6.77 × 10⁴ cm³ mol⁻¹ s⁻¹. The pseudo steady-state polarization method was employed to investigate the electrocatalytic oxidation of methanol at the Ni/Zn/Al LDH-MOFs/CCE, as well as to determine some electrooxidation reaction parameters. The obtained values include the following: k₂Г^* = 1.87 × 10⁻⁹ cm s⁻¹ and the ratio of k⁰₋₁/k⁰₁ = 1.8 × 10⁷. These findings indicated that the incorporation of the Zn ions and MOFs into the Ni/Al LDH and the construction of the nanocomposite significantly enhanced the electrocatalytic performance of the resulting electrocatalyst, paving the way for the development of a highly efficient anodic material for direct methanol fuel cell applications.