The presence of high nitrate (NO₃⁻) concentration in natural water constitutes a serious issue to the environment and human health. Therefore, the development of low-cost, stable non-precious metal catalysts is imminent for efficient NO₃- reduction. In this study, we prepared a Co₃O₄-TiO₂/Ti cathode via combining sol-gel and calcination methods and evaluated its performance for electrocatalytic NO₃- reduction. The dispersion of the Co₃O₄ catalyst particles was improved by the addition of PVP to the coating liquid. The presence of anatase could effectively stabilize Co₃O₄ and prevent the releasing of toxic Co ions into the solution. The Co₃O₄-TiO₂/Ti cathode with the optimized performance for NO₃- reduction could be prepared by four times coating at calcination temperature of 500 °C. The electrocatalytic reduction of NO₃- was negligibly impacted by solution pH in the range of 3.0–9.0, while it could be facilitated by elevating the current density from 2.5 to 25 mA cm². Ammonium ions were the main final NO₃- reduction product, and the presence of Cl- was capable to oxidize ammonium ions to N₂ due to the electrochemical production of reactive chlorine species. The electrochemical analyses, scavenging experiments and density functional theory calculations collectively confirm that NO₃- reduction was mainly induced by the Co²⁺–Co³⁺–Co²⁺ redox process instead of being directly resulted from the electrons generated at the cathode. Unlike noble metal (e.g., Pd and Ag) based catalytic reaction systems, in the present Co₃O₄ mediated electrocatalytic reaction process, atomic H* would more favorably turn to H₂ by Heyrovsky and Tafel routes and therefore contributed marginally to the NO₃- reduction. Generally, this study provided a new paradigm for designing the stable and cost-effective cathode for NO₃- reduction.

高硝酸盐（NO的存在₃ ^- ）天然水浓度构成了严重的问题，对环境和人类健康。因此，迫切需要开发低成本，稳定的非贵金属催化剂，以有效地还原NO ₃。在这项研究中，我们通过结合溶胶-凝胶法和煅烧方法制备了一个Co ₃ O ₄ -TiO ₂ / Ti阴极，并评估了其电催化还原NO _3的性能。通过向涂布液中添加PVP，改善了Co ₃ O ₄催化剂颗粒的分散性。锐钛矿的存在可以有效地稳定Co ₃ O _4。并防止有毒的Co离子释放到溶液中。通过在500°C的煅烧温度下进行四次涂覆，可以制备出具有优化的NO _3-还原性能的Co ₃ O ₄ -TiO ₂ / Ti阴极。在溶液pH值在3.0-9.0范围内，NO _3-的电催化还原影响可忽略不计，而将电流密度从2.5 mA cm ²升高至25 mA cm ²则可以促进还原。铵离子是最终的主要NO _3-还原产物，而Cl-的存在能够将铵离子氧化为N _2。由于反应性氯物种的电化学生产。电化学分析，清除实验和密度泛函理论计算共同证实，NO _3-还原主要是由Co ²⁺ -Co ³⁺ -Co ²⁺氧化还原过程引起的，而不是直接由阴极产生的电子引起的。与基于贵金属（例如，Pd和Ag）的催化反应系统不同，在当前的Co ₃ O ₄介导的电催化反应过程中，原子H *通过Heyrovsky和Tafel路线更有利地变为H ₂，因此对NO _3的贡献很小。- 减少。通常，这项研究为设计稳定且具有成本效益的NO _3-还原阴极提供了新的范例。