Enhanced Charge Carrier Dynamics on Sb2 Se3 Photocathodes for Efficient Photoelectrochemical Nitrate Reduction to Ammonia

Abstract

Ammonia (NH₃ ) is recognized as a transportable carrier for renewable energy fuels. Photoelectrochemical nitrate reduction reaction (PEC NO₃ 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 NO₃ RR by constructing a CoCu/TiO₂ /Sb₂ Se₃ photocathode. The constructed CoCu/TiO₂ /Sb₂ Se₃ 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/TiO₂ /Sb₂ Se₃ 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 NO₃ 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 NO₃ RR activity on CoCu/TiO₂ /Sb₂ Se₃ . This work provides a new avenue for the feasibility of efficient PEC ammonia synthesis from nitrate-rich wastewater.

Keywords: CoCu catalyst; Sb2Se3 photocathode; ammonia synthesis; charge transfer; high Faradaic efficiency; photoelectrochemical nitrate reduction.