Boosting the electrocatalytic activity of nitrobenzene reduction via d-d orbital hybridization in dual-atom catalysts

Aniline (PhNH 2 ) finds widespread applications in dyes, pharmaceuticals, pesticides, rubber additives, and the polyurethane industry. However, PhNH 2 is traditionally synthesized from nitrobenzene (PhNO 2 ) via hydrogenation under harsh conditions (high-temperature and high-pressure). Hence, developing highly active catalysts for the electrocatalytic hydrogenation of PhNO 2 under mild operating conditions is of paramount importance for both aniline synthesis and electrochemical energy storage technologies. Herein, twenty-five Co-TM-N 6 V 4 -G dual-atom catalysts (DACs) were constructed by coupling a Co single atom with various transition metal (TM) species. Density functional theory (DFT) calculations were performed to elucidate how interatomic d–d orbital coupling within the DACs regulates their catalytic performance toward nitrobenzene electroreduction. First, evaluations of the formation energies, dissolution potentials, and the differences between average binding and cohesive energies indicate that all 25 DACs exhibit excellent thermodynamic and electrochemical stability. Second, Gibbs free energy profiles and limiting potential calculations reveal that the Co-Cu-N 6 V 4 -G catalyst possesses the optimal catalytic activity and selectivity. Insights into the electronic structure and synergistic mechanism of Co-Cu-N 6 V 4 -G reveal that Cu single-atom doping successfully promotes d–d orbital hybridization between the adjacent Cu and Co atoms. Such electronic modulation substantially strengthens the adsorption and activation of the reactant, thereby lowering the thermodynamic barrier of the potential-determining step (PDS). Consequently, this work establishes a solid theoretical foundation for the rational design of advanced DACs toward efficient PhNO 2 electroreduction.