Graphene-supported platinum/nickel phosphide electrocatalyst with improved activity and stability for methanol oxidation

Design of Self-Supported Flexible Nanostars MFe-LDH@ Carbon Xerogel-Modified Electrode for Methanol Oxidation

Layered double hydroxides (LDHs) have emerged as promising electrodes materials for the methanol oxidation reaction. Here, we report on the preparation of different LDHs with the hydrothermal process. The effect of the divalent cation (i.e., Ni, Co, and Zn) on the electrochemical performance of methanol oxidation was investigated. Moreover, nanocomposites of LDHs and carbon xerogels (CX) supported on nickel foam (NF) substrate were prepared to investigate the role of carbon xerogel. The results show that NiFe-LDH/CX/NF is an efficient electrocatalyst for methanol oxidation with a current density that reaches 400 mA·m-2 compared to 250 and 90 mA·cm-2 for NiFe-LDH/NF and NF, respectively. In addition, all LDH/CX/NF nanocomposites show excellent stability for methanol oxidation. A clear relationship is observed between the electrodes crystallite size and their activity to methanol oxidation. The smaller the crystallite size, the higher the current density delivered. Additionally, the presence of carbon xerogel in the nanocomposites offer 3D interconnected micro/mesopores, which facilitate both mass and electron transport.

Nanohybrid layered double hydroxide materials as efficient catalysts for methanol electrooxidation

In this work, efficient methanol oxidation fuel cell catalysts with excellent stability in alkaline media have been synthesized by including transition metals to the layered double hydroxide (LDH) nanohybrids. The nanohybrids CoCr-LDH, NiCoCr-LDH and NiCr-LDH were prepared by co-precipitation and their physicochemical characteristics were investigated using TEM, XRD, IR and BET analyses. The nanohybrid CoCr-LDH is found to have the highest surface area of 179.87 m² g⁻¹. The electrocatalytic activity measurements showed that the current density was increased by increasing the methanol concentration (from 0.1 to 3 M) as a result of its increased oxidation at the surface. The nanohybrid NiCr-LDH, showing the highest pore size (55.5 Å) showed the highest performance for methanol oxidation, with a current density of 7.02 mA cm⁻² at 60 mV s⁻¹ using 3 M methanol. In addition, the corresponding onset potential was 0.35 V (at 60 mV s⁻¹ using 3 M methanol) which is the lowest value among all other used LDH nanohybrids. Overall, we observed the following reactivity order: NiCr-LDH > NiCoCr-LDH > CoCr-LDH, as derived from the impedance spectroscopy analysis.

Methanol electrooxidation over layered double hydroxides.