Efficient Electroreduction of Low Nitrate Concentration via Nitrate Self-Enrichment and Active Hydrogen Inducement on the Ce(IV)-Co<sub>3</sub>O<sub>4</sub> Cathode
Changhui Zhou, Yan Zhang, Chaoyue Xie, Jing Bai, Jinhua Li, Haichuan Zhang, Hong Zhu, Mingce Long, Baoxue Zhou, Gengfeng Zheng
Abstract
Low concentrations of nitrate (NO 3 – ) widely exist in wastewater, post-treated wastewater, and natural environments; its further disposal is a challenge but meaningful for its discharge goals. Electroreduction of NO 3 – is a promising method that allows to eliminate NO 3 – and even generate higher-value NH 3 . However, the massive side reaction of hydrogen evolution has raised great obstacles in the electroreduction of low concentrations of NO 3 – . Herein, we present an efficient electroreduction method for low or even ultralow concentrations of NO 3 – via NO 3 – self-enrichment and active hydrogen (H*) inducement on the Ce(IV)-Co 3 O 4 cathode. The key mechanism is that the strong oxytropism of Ce(IV) in Co 3 O 4 resulted in two changes in structures, including loose nanoporous structures with copious dual adsorption sites of Ce–Co showing strong self-enrichment of NO 3 – and abundant oxygen vacancies (O vs ) inducing substantial H*. Ultimately, the bifunctional role synergistically promoted the selective conversion of NH 3 rather than H 2 . As a result, Ce(IV)-Co 3 O 4 demonstrated a NO 3 – self-enrichment with a 4.3-fold up-adsorption, a 7.5-fold enhancement of NH 3 Faradic efficiency, and a 93.1% diminution of energy consumption when compared to Co 3 O 4, substantially exceeding other reported electroreduction cathodes for NO 3 – concentrations lower than 100 mg·L –1 . This work provides an effective treatment method for low or even ultralow concentrations of NO 3 – .