Heteroatom-Coordinated Palladium Molecular Catalysts for Sustainable Electrochemical Production of Hydrogen Peroxide
Endalkachew Asefa Moges, Chia‐Yu Chang, Wei‐Hsiang Huang, Fikiru Temesgen Angerasa, Keseven Lakshmanan, Teklay Mezgebe Hagos, Habib Gemechu Edao, Woldesenbet Bafe Dilebo, Chi-Wen Pao, Meng‐Che Tsai, Wei‐Nien Su, Bing‐Joe Hwang
Abstract
Currently, hydrogen peroxide (H 2 O 2 ) manufacturing involves an energy-intensive anthraquinone technique that demands expensive solvent extraction and a multistep process with substantial energy consumption. In this work, we synthesized Pd–N 4 -CO, Pd–S 4 –NCO, and Pd–N 2 O 2 –C single-atom catalysts via an in situ synthesis approach involving heteroatom-rich ligands and activated carbon under mild reaction conditions. It reveals that palladium atoms interact strongly with heteroatom-rich ligands, which provide well-defined and uniform active sites for oxygen (O 2 ) electrochemically reduced to hydrogen peroxide. Interestingly, the Pd–N 4 –CO electrocatalyst shows excellent performance for the electrocatalytic reduction of O 2 to H 2 O 2 via a two-electron transfer process in a base electrolyte, exhibiting a negligible amount of onset overpotential and >95% selectivity within a wide range of applied potentials. The electrocatalysts based on the activity and selectivity toward 2e – ORR follow the order Pd–N 4 –CO > Pd–N 2 O 2 –C > Pd–S 4 –NCO in agreement with the pull–push mechanism, which is the Pd center strongly coordinated with high electronegativity donor atoms (N and O atoms) and weakly coordinated with the intermediate *OOH to excellent selectivity and sustainable production of H 2 O 2 . According to density functional theory, Pd–N 4 is the active site for selectivity toward H 2 O 2 generation. This work provides an emerging technique for designing high-performance H 2 O 2 electrosynthesis catalysts and the rational integration of several active sites for green and sustainable chemical synthesis via electrochemical processes.