Enhanced Charge Carrier Dynamics on Sb 2 Se 3 Photocathodes for Efficient Photoelectrochemical Nitrate Reduction to Ammonia.

Ammonia (NH 3 ) is recognized as a transportable carrier for renewable energy fuels. Photoelectrochemical nitrate reduction reaction (PEC NO 3 RR) 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 NO 3 RR by constructing a CoCu/TiO 2 /Sb 2 Se 3 photocathode. The constructed CoCu/TiO 2 /Sb 2 Se 3 photocathode achieves an ammonia Faraday efficiency (FE) of 88.01 % at -0.2 V RHE and an ammonia yield as high as 15.91 μmol h -1  cm -2 at -0.3 V RHE with an excellent onset potential of 0.43 V RHE . Dynamics experiments and theoretical calculations have demonstrated that the CoCu/TiO 2 /Sb 2 Se 3 photocathode possesses high light absorption capacity, excellent carrier transfer capability, and high charge separation and transfer efficiencies. The photocathode can effectively adsorb the reactant NO 3 - and intermediate, and the CoCu co-catalyst increases the maximum Gibbs free energy difference between NO 3 RR 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 NO 3 RR activity on CoCu/TiO 2 /Sb 2 Se 3 . This work provides a new avenue for the feasibility of efficient PEC ammonia synthesis from nitrate-rich wastewater.