Trapped interfacial redox introduces reversibility in the oxygen reduction reaction in a non-aqueous Ca2+ electrolyte

Effect of alkali-metal cation on oxygen adsorption at Pt single-crystal electrodes in non-aqueous electrolytes

The effect of Group 1 alkali-metal cations (Na+, K+, and Cs+) on the oxygen reduction and evolution reactions (ORR and OER) using dimethyl sulfoxide (DMSO)-based electrolytes was investigated. Cyclic voltammetry (CV) utilising different Pt-electrode surfaces (polycrystalline Pt, Pt(111) and Pt(100)) was undertaken to investigate the influence of surface structure upon the ORR and OER. For K+ and Cs+, negligible variation in the CV response (in contrast to Na+) was observed using Pt(111), Pt(100) and Pt(poly) electrodes, consistent with a weak surface-metal/superoxide complex interaction. Indeed, changes in the half-wave potentials (E1/2) and relative intensities of the redox peaks corresponding to superoxy (O2-) and peroxy (O22-) ion formation were consistent with a solution-mediated mechanism for larger cations, such as Cs+. Support for this finding was obtained via in situ shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS). During the ORR and in the presence of Cs+, O2- and weakly adsorbed caesium superoxide (CsO2) species were detected. Because DMSO was found to strongly interact with the surface at potentials associated with the ORR, CsO2 was readily displaced at more negative potentials via increased solvent adsorption at the surface. This finding highlights the important impact of the solvent during ORR/OER reactions.

Robust Oxygen Reduction Electrocatalysis Enabled by Platinum Rooted on Molybdenum Nitride Microrods

Robust oxygen reduction electrocatalysis is central to renewable fuel cells and metal-air batteries. Herein, Pt nanoparticles (NPs) rooted on porous molybdenum nitride microrods (Pt/Mo₂N MRs) are rationally constructed toward the oxygen reduction reaction (ORR). Owing to the desired composition with strong electronic metal-support interactions (EMSIs) and a porous one-dimensional structure supporting ultrafine NPs, the developed Pt/Mo₂N MRs possess much higher ORR mass and specific activities than commercial Pt/C. In situ Raman and density functional theory calculations reveal that the EMSI weakens the adsorption of intermediates over Pt/Mo₂N MRs via an associative mechanism. Moreover, the porous Mo₂N support stabilizes these high activities. Impressively, a homemade zinc-air battery driven by Pt/Mo₂N MRs delivers excellent performance including a peak power density of 167 mW cm^-2 and a high rate capability that ranged from 5 to 50 mA cm^-2. This work highlights the role of EMSI in promoting robust ORR electrocatalysis, thus providing a promising approach for efficient and robust cathode materials for advanced metal-air batteries.