Enhanced Charge Carrier Dynamics on Sb2Se3 Photocathodes for Efficient Photoelectrochemical Nitrate Reduction to Ammonia

Ammonia (NH3) is recognized as a transportable carrier for renewable energy fuels. Photoelectrochemical nitrate reduction reaction (PEC NO3RR) offers a sustainable solution for nitrate‐rich wastewater treatment by directly converting solar energy to ammonia. In this study, we demonstrate the highly selective PEC ammonia production from NO3RR by constructing a CoCu/TiO2/Sb2Se3 photocathode. The constructed CoCu/TiO2/Sb2Se3 photocathode achieves an ammonia Faraday efficiency (FE) of 88.01 % at −0.2 VRHE and an ammonia yield as high as 15.91 μmol h−1 cm−2 at −0.3 VRHE with an excellent onset potential of 0.43 VRHE. Dynamics experiments and theoretical calculations have demonstrated that the CoCu/TiO2/Sb2Se3 photocathode possesses high light absorption capacity, excellent carrier transfer capability, and high charge separation and transfer efficiencies. The photocathode can effectively adsorb the reactant NO3− and intermediate, and the CoCu co‐catalyst increases the maximum Gibbs free energy difference between NO3RR and HER. Meanwhile, the Co species enhances the spin density of Cu, and increases the density of states near the Fermi level in pdos, which results in a high PEC NO3RR activity on CoCu/TiO2/Sb2Se3. This work provides a new avenue for the feasibility of efficient PEC ammonia synthesis from nitrate‐rich wastewater. The highly selective photoelectrochemical ammonia production from NO3 reduction reaction can be achieved by constructing a CoCu/TiO2/Sb2Se3 photocathode. The photocathode achieves an ammonia Faraday efficiency of 88.01 % and an ammonia yield as high as 15.91 μmol h−1 cm−2 with an excellent onset potential of 0.43 VRHE. It provides a new avenue for the feasibility of efficient PEC ammonia synthesis from nitrate‐rich wastewater.