The electrochemical performance of Ni-based MONs towards peroxide synthesis was next studied with rotating ring disk electrode (RRDE) system in aqueous 1 M KOH electrolyte. To do so, a catalyst in was first prepared form the dry MONs in an ethanol/water/nafion/carbon nanotube (CNT) dispersion, which was subsequently drop cast onto the working electrode. In an O2-saturated electrolyte, each MON featured a current onset around 0.8 VRHE (Fig. ). However, the ring, used to oxidize peroxide (HO2 -in alkaline electrolyte), revealed stark differences between their selectivity. The Ni-MON and Ni-F-MON exhibited rather low peroxide selectivity on the order of 45-70% (Fig. ). In contrast, the Ni-Amine-MON featured selectivity above 90% from 0.45VRHE. The mass loading of the MONs (0.2mg/cm 2 ) was identical for all catalysts and the quantity of electrochemically accessible Ni sites (Fig. ) was similar so changes in peroxide selectivity are attributed to intrinsic differences between the catalysts. This is also reflected in their differing Tafel slopes (Fig. ), in which the higher peroxide selectivity is correlated with higher Tafel slope values. While we do could not extensively characterize the MONs after electrochemical experiments on an RRDE, we measured their XRD patterns after prolonged electrolysis on a carbon paper electrode instead (Fig. ). The results indicate that the MONs unexpectedly lose their long-range crystallinity during the process and only very weak peaks attributed to a residual LDH phase remain. Likely, during the RRDE measurements, the MONs likely lose their long-range order as well, though retain the local coordination that gives rise to their differing performance. To translate our initial catalytic results to a practical peroxide electrosynthesis system, we moved to use a gas-diffusion electrode setup (Fig. ). To do so, we deposited the same catalyst ink on a gas diffusion electrode, featuring a gas-permeable support and surface, which enabled us to circumvent the low solubility of O2 in aqueous solutions. As the Ni-Amine-MON featured the highest selectivity for peroxide in RRDE measurements, this was our chosen material for further analysis. The peroxide produced was quantified through a simple Ce 4+ -based colorimetric assay after prolonged (approx. 30 min) electrolysis times (Fig. ). The partial current density attributed to peroxide production started to slowly increase at 0.72VRHE and reached an impressive ~200 mA/cm 2 at 0.52VRHE (Fig. ), after which it began to slightly drop as the 4e - oxygen reduction pathway began to contribute. At this high partial current density, the FE for peroxide 85% (Fig. ). These metrics are comparable to the highest performing state-of-the-art systems recently published. Further, the system could continually produce peroxide for upwards of 75 hours (Fig. ).