Asymmetric coordinated single-atom Pd sites for high performance CO₂ electroreduction and Zn–CO₂ battery

Single-atom catalysts (SACs) have attracted great attention for electrocatalysis. The coordination configurations of heteroatoms surrounding the metal center have a significant influence on the catalytic performance. The construction of asymmetric coordination configurations has recently been found to be an efficient strategy to improve electrocatalytic performance. However, noble-metal-based SACs with an asymmetric coordination environment have seldom been achieved. Herein, we rationally design and construct single-atom Pd catalysts with asymmetric Pd₁O₃C₁ or Pd₁N₃C₁ sites anchored on oxidized mesoporous carbon with optimized porosity and hydrophobicity. The as-prepared catalyst (Pd1-O-CB) selectively produces CO with a high CO Faradaic efficiency (FE_CO) of 99.6 % at a low potential of –0.6 V versus reversible hydrogen electrode (RHE). Furthermore, the Pd1-O-CB-based gas diffusion layer exhibits a high current density of 280.4 mA cm⁻² and long-term stability over 48 h benefitted from the regulated porosity and hydrophobicity of the tri-interface. Finally, a rechargeable Zn–CO₂ battery is constructed with the optimal gas diffusion electrode to deliver a maximal power density of 1.72 mW cm⁻².