Pd-N-C shelled Pd nanoparticle catalysts for high-performance hydrogen peroxide electrosynthesis

Metal-nitrogen-carbon (M-N-C) catalysts have attracted widespread attention due to their potential in promoting the electrochemical oxygen reduction reaction (ORR) for the selective production of hydrogen peroxide (H₂O₂). However, the effects of their diverse structures and complex compositions on the catalytic performance remain poorly understood. Herein, systematic theoretical calculations reveal that the Pd-N-C based single-atom catalyst featuring a 1 : 1 ratio of pyridinic and pyrrolic nitrogen adopts a centrosymmetric PdN₄ structure (Pd_SAN_2-2C), and the Pd d_z² orbital can strongly interact with the O 2p orbital of the adsorbed OOH intermediate, thereby strengthening its adsorption and facilitating subsequent conversion to H₂O₂. Guided by the theoretical insights, the Pd_SAN_2-2C catalyst and a novel Pd@Pd_SAN_2-2C core-shell catalyst with Pd nanoparticles encapsulated by an ultrathin Pd_SAN_2-2C shell are synthesized, and the latter exhibits a remarkable H₂O₂ selectivity of 97% and a high yield of 35.88 mol g _cat ^-1 h^-1 at an industrially relevant current density of 200 mA cm^-2, along with superior operational stability. This combined theoretical and experimental study provides useful guidance for the rational design of high-efficiency M-N-C catalysts for selective electrocatalysis.