Catalytic Isotope Effects of 107 Ag/ 109 Ag in the Photocatalytic Degradation of Methyl Orange

Nuclear structure and properties are mainly studied by utilizing large-scale equipment such as colliders, while the chemical behavior of isotopes and their isotopologues emerges as a critical approach to investigating nuclei. Studies of isotope effects (IEs) primarily focus on the isotope separation or kinetic isotope effects of light isotopes such as H/D/T caused by mass-dependent IEs. However, barely any study has investigated whether the neutral neutron could remarkably influence medium-heavy isotopes as catalysts, since they are usually regarded as chemically similar, exhibiting inapparent mass differences. Herein, we revealed a remarkable IE of 107 Ag and 109 Ag with the photogenerated ability of their Ag 2 O isotopologues, 107 Ag 2 O and 109 Ag 2 O, exceeding 19.9%, despite a mass difference of less than 2%. Based on this IE in photochemistry, we processed methyl orange degradation as the model reaction and obtained an unprecedented IE k 107 / k 109 = 1.1 with 107 Ag 2 O and 109 Ag 2 O serving as photocatalysts, respectively. The correlation of extranuclear electrons and the nucleus has been quantified for the first time by both theoretical calculations and experimental results, which is proportional to the Ag isotopes’ nuclear charge density. This work extends our fundamental understanding of how the “humble” neutron affects extranuclear electrons during the photochemical process.