Conjugated Nickel Phthalocyanine Derivatives for Heterogeneous Electrocatalytic H₂O₂ Synthesis

Electrocatalytic hydrogen peroxide (H₂O₂) production has emerged as a promising alternative to the chemical method currently used in industry, due to its environmentally friendly conditions and potential for higher activity and selectivity. Heterogeneous molecular catalysts are promising in this regard, as their active site configurations can be judiciously designed, modified, and tailored with diverse functional groups, thereby tuning the activity and selectivity of the active sites. In this work, nickel phthalocyanine derivatives with various conjugation degrees are synthesized and identified as effective pH-universal electrocatalysts for H₂O₂ production after heterogenized on nitrogen-decorated carbon, with increased conjugation degrees leading to boosted selectivity. This is explained by the regulated d-band center, which optimized the binding energy of the reaction intermediate, reducing the energy barrier for oxygen reduction and leading to optimized H₂O₂ selectivity. The best catalyst, NiPyCN/CN, exhibits a high H₂O₂ electrosynthesis activity with ≈95% of H₂O₂ faradic efficiency in an alkaline medium, demonstrating its potential for H₂O₂ production.