Surface iodine and pyrenyl-graphdiyne co-modified Bi catalysts for highly efficient CO₂ electroreduction in acidic electrolyte

CO₂ electroreduction to formic acid/formate would contribute to alleviating the energy and climate crisis. This work reports a Bi-based catalyst derived from the in-situ electroreduction of Bi₂O₂CO₃ modified with iodine and pyrenyl-graphdiyne (PGDY) on the surface for efficient electroreduction of CO₂ in acidic electrolyte, with a high partial current density of 98.71 mA·cm⁻² and high Faradaic efficiency (FE) > 90% over the potential range from −1.2 to −1.5 V vs. reversible hydrogen electrode (RHE), as well as the long-term operational stability over 240 h without degradation in H-type cell. Experimental results and density function theory calculations show that the synergistic effect of surface iodine and PGDY is responsible for this active and extremely stable process of CO₂ electroreduction via lowering the energy barriers for formation of *OCHO intermediate, suppressing the competitive HER by enhancing the concentration of both K⁺ and CO₂ at reaction interface, as well as preventing the dissolution and re-deposition of active Bi atoms on surface during catalytic reaction. This work provides new insight into designing highly active and stable electrocatalysts for CO₂ reduction.