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.

A visible-light-response, efficient and robust photo-catalyst for CO₂ reduction is highly desirable. Herein, we demonstrate that single titanium-oxide species implanted in two-dimensional (2D) graphitic carbon nitride (g-C₃N₄) matrix (2D TiO-CN) can efficiently photo-catalyze the reduction of CO₂ to CO under the irradiation of visible light. The synergistic interaction between single titanium oxide species and g-C₃N₄ in 2D TiO-CN not only enhances the separation of photo-excited charges, but also results in visible light response of single titanium-oxide species, realizing high activity of CO₂ photo-reduction with extremely high CO generation rate of 283.9 μmol·h⁻¹·g⁻¹, 5.7, 6.8 and 292.2 times larger than those of TiO₂/CN hybrid material, CN and commercial TiO₂, respectively. Time-resolved fluorescence and electron spin resonance spectroscopy revealed the catalytic mechanism of the fabricated 2D TiO-CN photocatalysts for CO₂ reduction.