Bimetallic Pt-Pd nanostructures supported on MoS 2 as an ultra-high performance electrocatalyst for methanol oxidation and nonenzymatic determination of hydrogen peroxide.

The authors report on a composite based electrocatalyst for methanol oxidation and H2 O2 sensing. The composite consists of Pt nanoparticles (NPs), Pd nanoflakes, and MoS2 . It was synthesized by chemical reduction followed by template-free electro-deposition of Pt NPs. FESEM images of the Pd nanoflakes on the MoS2 reveal nanorod-like morphology of the Pd NPs on the MoS2 support, whilst FESEM images of the Pt-Pd/MoS2 composite show Pt NPs in high density and with the average size of ~15 nm, all homogeneously electrodeposited on the Pd-MoS2 composite. A glassy carbon electrode (GCE) was modified with the composite to obtain an electrode for methanol oxidation and H2 O2 detection. The modified GCE exhibits excellent durability with good catalytic efficiency (the ratio of forward and backward peak current density, If /Ib , is 3.23) for methanol oxidation in acidic medium. It was also used to sense H2 O2 at an applied potential of -0.35 V vs. Ag|AgCl which can be detected with a 3.4 μM lower limit of detection. The sensitivity is 7.64 μA μM-1  cm-2 and the dynamic range extends from 10 to 80 μM. This enhanced performance can be explained in terms of the presence of higher percentage of metallic 1T phase rather than a semiconducting 2H phase in MoS2 . In addition, this is a result of the high surface area of MoS2 with interwoven nanosheets, the uniform distribution of the Pt NPs without any agglomeration on MoS2 support, and the synergistic effect of Pt NPs, Pd nanoflakes and MoS2 nanosheets. In our perception, this binder-free nano-composite has promising applications in next generation energy conversion and in chemical sensing. Graphical abstract A composite consisting of palladium nanoflakes and molybdenum disulfide was decorated with platinum nanoparticles and then placed on a glassy carbon electrode which is shown to be a viable electrocatalyst for both methanol oxidation and detection of hydrogen peroxide.