Polyaniline supported g-C3N4 quantum dots surpass benchmark Pt/C: Development of morphologically engineered g-C3N4 catalysts towards “metal-free” methanol electro-oxidation

Abstract

In spite of being one of the most promising energy conversion devices, the state of the art in the efficient application of direct methanol fuel cell is far from being optimal mostly because of its heavy reliance on expensive Pt anode that suffers from easy CO poisoning. Here, in this work for the first time in literature, we have explored the catalytic efficacy and improved mass activity of morphologically engineered metal-free graphitic carbon nitride towards methanol oxidation. The 2D nano-sheets, 1D nano-rods, and 0D quantum dots of graphitic carbon nitride are successfully prepared from bulk by a thermo-chemical etching process. The materials are thoroughly characterized with the help of X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, luminescence study and are studied for methanol oxidation reaction in basic condition with the help of cyclic voltammetry. Among the three different dimensional g-C3N4 materials, the quantum dots show higher methanol oxidation activity due to its abundant edges in nano morphology and maximum atomic percentages of active site of pyridinic N. The 0D g-C3N4 when supported on conducting polyaniline, not only shows higher electrocatalytic methanol oxidation activity than the commercial Pt/C but also demonstrates excellent CO tolerance to be a suitable and applicable metal-free anode catalyst in direct methanol fuel cell applications. The electrostatic interaction between 0D g-C3N4 and conducting polyaniline (PANI) fibres may have improved the electrical conductivity and methanol adsorption of CNQD-PANI electrocatalyst and also played a role in oxidizing the adsorbed CO to upsurge the CO tolerance.