ABSTRACT
Chlorine evolution reaction (CER) is crucial for industrial-scale production of high-purity Cl2. Despite the development of classical dimensionally stable anodes to enhance CER efficiency, the competitive oxygen evolution reaction (OER) remains a barrier to achieving high Cl2 selectivity. Herein, a binder-free electrode, Ru nanoparticles (NPs)-decorated NiMoO4 nanorod arrays (NRAs) supported on Ti foam (Ru-NiMoO4/Ti), was designed for active CER in saturated NaCl solution (pH = 2). The Ru-NiMoO4/Ti electrode exhibits a low overpotential of 20 mV at 10 mA cm-2 current density, a high Cl2 selectivity exceeding 90%, and robust durability for 90h operation. The marked difference in Tafel slopes between CER and OER indicates the high Cl2 selectivity and superior reaction kinetics of Ru-NiMoO4/Ti electrode. Further studies reveal a strong metal-support interaction (SMSI) between Ru and NiMoO4, facilitating electron transfer through the Ru-O bridge bond and increasing the Ru 3d-Cl 2p antibonding orbital occupancy, which eventually results in weakened Ru-Cl bonding, promoted Cl desorption, and enhanced Cl2 evolution. Our findings provide new insights into developing electrodes with enhanced CER performance through antibonding orbital occupancy engineering.
ABSTRACT
Chlorine evolution reaction (CER) is a commercially valuable electrochemical reaction used at an industrial scale. However, oxygen evolution reaction (OER) during the electrolysis process inevitably leads to the decreased efficiency of CER. It is necessary to improve the selectivity of CER by minimizing or even eliminating the occurrence of OER. Herein, a ternary metal oxide (Ru0.4Sn0.3Ti0.3) electrode was fabricated and employed as an active and robust anode for CER. The Ru0.4Sn0.3Ti0.3 electrode exhibits an excellent CER performance in 6.0 M NaCl solution, with a low potential of 1.17 V (vs. saturated calomel electrode, SCE) at 200 mA cm-2 current density, a high Cl2 selectivity of over 90 %, and robust durability after consecutive operation for 160 h under 100 mA cm-2. The maximum O2-Cl2 potential difference between OER and CER further demonstrates the high Cl2 selectivity of Ru0.4Sn0.3Ti0.3 electrode. Theoretical studies show that the strong Ru 3d-Ti 3d orbitals hybridization effect makes the d-band center (εd) of Ru 3d and Ti 3d orbitals positively and negatively shifted, respectively, endowing Ru site with enhanced Cl adsorption ability (i.e. enhanced Ru-Cl interaction) and Ru0.4Sn0.3Ti0.3 electrode with superior CER activity. This work offers valuable insights into the development of advanced electrodes for CER in practical application.