Hydrogen Peroxide Synthesis via Enhanced Two-Electron Oxygen Reduction Pathway on Carbon-Coated Pt Surface

Abstract

Continuous on-site electrochemical production of hydrogen peroxide (H 2 O 2 ) can provide an attractive alternative to the present anthraquinone-based H 2 O 2 production technology. A major challenge in the electrocatalyst design for H 2 O 2 production is that O 2 adsorption on the Pt surface thermodynamically favors "side-on" configuration over "end-on" configuration, which leads to a dissociation of O−O bond via dominant 4-electron pathway. This prefers H 2 O production rather than H 2 O 2 production during the electrochemical oxygen reduction reaction (ORR). In the present work, we demonstrate that controlled coating of Pt catalysts with amorphous carbon layers can induce selective end-on adsorption of O 2 on the Pt surface by eliminating accessible Pt ensemble sites, which allows significantly enhanced H 2 O 2 production selectivity in the ORR. Experimental results and theoretical modeling reveal that 4-electron pathway is strongly suppressed in the course of ORR due to a thermodynamically unfavored end-on adsorption of O 2 (the first electron transfer step) with 0.54 V overpotential. As a result, the carbon-coated Pt catalysts show an onset potential of ∼0.7 V for ORR and remarkably enhanced H 2 O 2 selectivity up to 41%. Notably, the produced H 2 O 2 cannot access the Pt surface due to the steric hindrance of the coated carbon layers, and thus no significant H 2 O 2 decomposition via disproportionation/ reduction reactions is observed. Furthermore, the catalyst shows superior stability without considerable performance degradation because the amorphous carbon layers protect Pt catalysts against the leaching and ripening in acidic operating conditions.

Mechanism of the Oxidation of 3,3′,5,5′‐Tetramethylbenzidine Catalyzed by Peroxidase‐Like Pt Nanoparticles Immobilized in Spherical Polyelectrolyte Brushes: A Kinetic Study

“…[43] The surface adsorbed hydroxyl radicals are unlikely to convert back to H 2 O 2 , because this is kinetically unfavorable. [43][44][45] Similar results were also reported when Ag, Au, and Pd nanoparticles are used as catalysts. [13,46,47] H 2 O 2 can also break down into water and oxygen through non-radical ways, [48,49] yet the generation of hydroxyl radicals determines the oxidizing properties.…”

Oxygen‐Tolerant Electrodes with Platinum‐Loaded Covalent Triazine Frameworks for the Hydrogen Oxidation Reaction

“…Particularly in the potential region more positive than + 0.6 V( E >+ 0.6 V), which is critical for the start-up/shut-down operation of PEFCs, [7] theORR current for Pt-CTF was less than 23 %of that generated by 20 wt %P t/C.T he lower ORR activity of the electrode prepared with 2.8 wt %Pt-CTF is attributed to the fact that only the 2e À pathway for generating hydrogen peroxide (H 2 O 2 )c an proceed on as ingle Pt atom. [9,10,19] Notably,t he ring current, which corresponds to the generation of H 2 O 2 as an ORR intermediate,d id not significantly differ between the two catalysts at E >+ 0.6 V ( Figure 3b). This property is critical for the long-term operation of PEFCs, as H 2 O 2 can degrade PEFC components,such as membranes and catalyst binders.…”

Solar‐Driven Production of Hydrogen Peroxide from Water and Dioxygen

“…Althoughv arious metal complexes are known to catalyze the four-electron/four-proton reduction of O 2 to produce H 2 O, [1][2][3][4][5][6][7][8][9][10][11] late-transition-metal complexes that contain Co, [121][122][123][124][125][126][127][128][129][130] Ni, [131,132] Cu, [133][134][135] Pt, [136][137][138] Pd, [139][140][141] andA u [140][141][142] have been reported to act as effective catalysts for selective two-electron/twoproton reduction of O 2 to produce H 2 O 2 .T his can be explained by the "oxo wall" theory articulated by Gray and Winkler,i n which mononuclear complexes that contain transition metals to the right of the Fe-Ru-Os group in the periodic table with tetragonal geometry will not form at erminal oxo complex due to electrostatic repulsion of electrons between do rbitalo f these metals and oxo ligand. [143,144] Thus, metal complexes composed of metals to the right of the Fe-Ru-Os group catalyzes selectivet wo-electron/two-protonr eduction of O 2 to produce H 2 O 2 by meanso fM ÀOb ond cleavageo fh ydroperoxo intermediate without formation of metal-oxo speciest hrough the OÀOb ond cleavage for the four-electron/four-proton re-ductionofO 2 to H 2 O.…”