How amorphous CoOx(OH)y-Pd nanocomposite endows high performance and durability in methanol oxidation reaction

Abstract

One key issue in designing electrocatalysts for methanol oxidation reaction (MOR) is to improve their durability because the dissociative adsorption of methanol molecule could produce CO-like intermediate to poison catalysts. Here, we propose a wet chemical route to anchor Pd nanoparticles on amorphous CoO_x(OH)_y nanoplates and show that such amorphous support prefers to bind OH from electrolyte during electrochemical reaction to increase surface OH coverage, helping remove the poisonous intermediates and recover active sites. Besides, the oxygen vacancies in the amorphous CoO_x(OH)_y enable to produce excess electrons that are transferred to Pd to facilitate rate-determining step of MOR. Furthermore, we have verified the synergistic effect between Pd species and the amorphous CoO_x(OH)_y nanoplate would generate more reactive oxygen species than the individual component catalyst to further enhance MOR activity. Consequently, the amorphous CoO_x(OH)_y-Pd nanocomposites deliver more excellent electrocatalytic performance of ∼7100 mA mg_Pd⁻¹ and higher stability by retaining 86 % activity after 400 electrochemical cycles than Pd-loaded crystalline Co(OH)₂ nanoplates. Notably, the leaching out of Pd component was overcome in our study, this catalyst can even work for more than 100 h without obvious activity loss. Such a strategy by integrating noble metal component with amorphous support shall open up a new avenue in smart design of MOR nanocatalysts with simplified synthesis routes and high activity yet low cost.