Solvent molecules form surface redox mediators in situ and cocatalyze O ₂ reduction on Pd

Abstract

Solvent molecules influence the reactions of molecular hydrogen and oxygen on palladium nanoparticles. Organic solvents activate to form reactive surface intermediates that mediate oxygen reduction through pathways distinct from reactions in pure water. Kinetic measurements and ab initio quantum chemical calculations indicate that methanol and water cocatalyze oxygen reduction by facilitating proton-electron transfer reactions. Methanol generates hydroxymethyl intermediates on palladium surfaces that efficiently transfer protons and electrons to oxygen to form hydrogen peroxide and formaldehyde. Formaldehyde subsequently oxidizes hydrogen to regenerate hydroxymethyl. Water, on the other hand, heterolytically oxidizes hydrogen to produce hydronium ions and electrons that reduce oxygen. These findings suggest that reactions of solvent molecules at solid-liquid interfaces can generate redox mediators in situ and provide opportunities to substantially increase rates and selectivities for catalytic reactions.

Overall photosynthesis of H2O2 by an inorganic semiconductor

“…S15 ; H 2 O 2 generation selectivity is defined as the ratio of electrons utilized for H 2 O 2 synthesis to the total number of electrons consumed). These results indicate that Pd, as a verified catalyst for selective H 2 O 2 synthesis 22 – 24 , steered the ORR on Mo:BiVO 4 from four-electron (O 2 + 4H + + 4e − → 2H 2 O) to two-electron (O 2 + 2H + + 2e − → H 2 O 2 ) processes. Moreover, the enhanced H 2 O 2 production selectivity with Pd loading was slightly perturbed by the presence of CoO x , likely attributed to improved H 2 O 2 decomposition (Fig.…”

Recent Developments of Microenvironment Engineering of Single‐Atom Catalysts for Oxygen Reduction toward Desired Activity and Selectivity

“…Ten years later, we have witnessed an increasing number of SACs gradually occupying irreplaceable position in different domains of heterogeneous catalysis, including ORR. [ 43,80,161–166 ]…”

Catalysis in Single Crystalline Materials: From Discrete Molecules to Metal‐Organic Frameworks

“…Generally, the heterogeneous catalysts exist in two forms: restricted in insoluble nanoparticles [13][14][15][16] or immobilized (non)covalently onto the surfaces of different substates. [17,18] It has been proved that enormous of organic and inorganic reactions including water splitting, [19] hydrogenation of double bonds, [20,21] aryl-aryl coupling reactions [22] and even controllable combustion reactions [23] could be catalyzed through heterogeneous catalytic approaches. Although the heterogeneous catalysts shows great potential in controlling catalytic cost, however, the two-dimensional surface catalysis mechanism leads to low usage efficiencies.…”