Fighting poison with poison: Enhancing the performance of oxygen reduction reaction on Pt(111) via trace halide ion addition

The sluggish kinetics of the cathodic oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs) and phosphoric acid fuel cells (PAFCs) remains a primary obstacle to their large-scale application. Anionic adsorbates, such as OH, sulfonate, and phosphate, are widely recognized as detrimental species that diminish ORR activity. In this study, we present a novel approach aimed at mitigating the poisoning effect of such adsorbates and enhancing ORR performance by modifying either the electrolyte or the electrode with trace amounts of stronger adsorbates—a concept termed “fighting poison with poison.” Our results demonstrate that the addition of minute quantities of halide ions (e.g., Cl− or Br−) to commonly used electrolytes (0.05 M H2SO4, 0.05 M H3PO4, and 0.10 M HClO4) or to the Pt(111) electrode surface significantly boosts ORR activity. The inhibitory effect of stronger adsorbates on the shielding effect of those commonly adsorbed weaker adsorbates is probably the origin of such enhancement. The insights gained and strategies developed for optimizing the ORR activity of Pt(111) in this study offer valuable guidance for the future development of efficient catalysts and the optimization of electrolytes for PEMFCs and PAFCs. [Display omitted] •“Fighting poison with poison”: Halide ions enhance ORR activity.•Trace Cl− and Br− added to electrolytes or Pt(111) surface boost ORR.•Volcano relationship observed between halide concentration and ORR performance.•Shielding effect of adsorbates crucial in modulating ORR activity.•Strategy offers potential for improving PEMFCs and PAFCs efficiency.