Combining a Pd Cluster and a Built-in Electric Field as a Biomimic for Stable C-Cl Bond Polarization.

Abstract

Adopting the essence of enzyme catalysis, the strong binding of substrates into the active site pocket for their selective activation through multiple noncovalent interactions in the reactive site design can effectively enhance the electrocatalysis process. However, mimicking the enzyme catalytic process, particularly the introduction of reactant activation mechanisms, remains a significant challenge. Herein, we present a Pd cluster inside the Fe₂N-Fe₃O₄-based built-in electric field (BEF), denoted as Pd/Fe₂N-Fe₃O₄, to serve as an enzyme mimic to activate stable C-Cl bonds. Theoretical calculations and in situ Raman indicate that the probe molecule 2,4-dichlorophenol (2,4-DCP) adsorbs onto the Pd site and rotates inside the BEF with the C₄-Cl bond being selectively activated and elongated from 1.73 to 1.82 Å. This makes Pd/Fe₂N-Fe₃O₄ an excellent electrocatalytic hydrodechlorination catalyst, with Pd usage down to 2.5 μg cm^-2, which is 32.7-360 times less than that of conventional catalysts like Pd/C, and achieving a Faradaic efficiency exceeding 20%. We reveal that besides H*-mediated electrochemical reduction, Pd/Fe₂N-Fe₃O₄ also hydrodechlorinates activated 2,4-DCP via the proton-electron coupled transfer pathway. This understanding of the role of BEF in reactant activation, along with the strategy of integrating BEF and noble metals to mimic enzymes, provides a direction for the design of advanced electrocatalysts.