On the Relevance of Edge and Corner Sites in the Electrocatalytic Production of H2O2 over Supported Ni Catalysts

Electrocatalytic hydrogen peroxide (H2O2) production, over Ni-based catalysts, through 2 electron oxygen reduction (ORR) is an environmentally friendly alternative compared to the traditional anthraquinone process. To understand catalytic performance in more detail, the geometrical particle size effect of nickel nanoparticles for this ORR reaction is investigated. The results show a linear relationship between both turnover frequency (TOF) and Faradaic efficiency (FE) with the number of edge and corner atoms in Ni particles ranging from 3.7–16.7 nm (Ni/carbon nanofiber catalysts). Edge and corner atoms catalyze the 2-electron reduction reaction, while facet atoms catalyze the 4-electron reduction reaction, confirming the presence of a geometrical particle size effect for the H2O2 production. It is hypothesized that the difference in selectivity is related to the mode of oxygen adsorption where the edges and corners favor the perpendicular binding (Pauling) orientation of oxygen, preserving the O─O bond and promoting H2O2 formation. While on facets O─O splitting is easier resulting in more OH−. This understanding of the role of edges/corners further enables more rational catalyst design.