Using mild photoelectrocatalytic technology to co-reduce CO₂ from the atmosphere and $NO_{2}^{-}$ from water pollutants into high-value-added chemical urea is an effective approach to achieving pollution reduction and carbon reduction goals. However, this reaction involves a 12-electron co-reduction with dual-substrate molecules, making it highly challenging with a complex pathway and high demands on the catalyst. So, there are few reports on this reaction currently. In this study, Ru, Cu, and Zn atom-modified TiO₂ catalytic materials (Ru, Cu, and Zn-TiO₂) were prepared via a hydrothermal method combined with photodeposition method. The specific synthesis processes are as follows: titanium butoxide was dropwise added into a H₂O/HCl mixed solution. Then the solution and fluorine-doped tin oxide (FTO) substrate were transferred and sealed in a Teflon-lined stainless-steel autoclave and heated to 150 ℃ for 20 h. The obtained TiO₂ photoelectrode was annealed in a muffle furnace at 350 ℃ for 2 h. The TiO₂ with different metal atom surface modifications were prepared by adding metal salt solution and methanol in a beaker, placing the TiO₂ photoelectrode in the solution and irradiating it with a 300 W xenon lamp for 1 h. We conducted catalytic urea synthesis experiments by using three-electrode configuration in a H-type quartz cell equipped with pretreated Nafion 117 membrane. The as-prepared semiconductor, Ag/AgCl electrode and Pt foil were utilized as the photocathode, reference and counter electrodes, respectively. 0.1 mol•L⁻¹ KNO₂ was used as the electrolyte in both the cathode and anode compartments. CO₂ gas was injected into the cathode chamber during the photoelectrocatalytic test. The experimental results showed that Ru-TiO₂ modified with 5% (w) Ru achieved a urea yield of 50.58 μmol•g⁻¹•h⁻¹ and a Faradaic efficiency (FE) of 16.66% under 2 h light irradiation at －0.1 V (vs. RHE). The 5% (w) Ru-TiO₂ catalyst exhibits a FE 1.65 times than that of TiO₂ under identical conditions. UV-Vis diffuse reflectance spectra (DRS) and electrochemical impedance spectra (EIS) indicate that Ru atoms can effectively enhance the light absorption, charge separation and transfer of TiO₂. Photogenerated electrons transfer from TiO₂ to Ru atomic sites, participating in the C—N coupling reaction. This work provides theoretical guidance for designing and synthesizing efficient catalysts for photoelectrocatalytic urea synthesis, offering novel idea and pathway for synergetic control of environmental pollution and carbon emissions.