International Journal of Hydrogen Energy, Vol.44, No.45, 24922-24933, 2019
Polyoxomolybdate anchored graphite oxide: Noble metal-free electrocatalyst for oxygen reduction reaction
We present the synthesis of a noble metal-free electrocatalyst, polyoxomolybdate/reduced graphite oxide (PMA/rGO) composite, which showed enhancement in the kinetics for oxygen reduction reaction (ORR). The composite material was prepared by simple and cost effective method. Mere heating of the precursors at low temperature (200 degrees C) resulted in molecular assembly of PMA on GO in the form of clusters which behaved as active centers for efficient ORR. The electrochemical study of PMA/rGO-2 (PMA to GO weight ratio of 1:2) catalyst carried out by rotating disk electrode (RDE) method, showed considerable electrocatalytic activity with E-onset of 1.0 V vs. RHE and current density of 4.0 mA/cm(2) at 1600 rpm in alkaline condition. Additionally, as-prepared PMA/rGO-2 catalyst showed a single step similar to 4 electron transfer pathway similar to commercial Pt/C catalyst; confirmed through rotating ring disk electrode (RRDE) study. Interestingly, PMA/rGO-2 electrocatalyst exhibited substantially higher stability than Pt/C catalyst even after 20K potential cycles (though the current density of former catalyst is inferior to later). Further, in a methanol cross-over test, PMA/rGO-2 was found to be inactive towards methanol oxidation reactions, which could nullify the issues due to the fuel cross-over effect, if employed as cathode in direct methanol fuel cells. The enhanced ORR activity and significant stability is attributable to the anchoring and homogenous distribution of polyoxomolybdate clusters on graphite oxide. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Keywords:Polyoxomolybdate;Graphite oxide;Noble metal-free electrocatalyst;Oxygen reduction reaction;Fuel cell