Rapid Conversion of Co2+ to Co3+ by Introducing Oxygen Vacancies in Co3O4 Nanowire Anodes for Nitrogen Removal with Highly Efficient H2 Recovery in Urine Treatment
At a Glance
Section titled āAt a Glanceā| Metadata | Details |
|---|---|
| Publication Date | 2022-06-24 |
| Journal | Environmental Science & Technology |
| Authors | Yan Zhang, Xiaoya Huang, Jinhua Li, Jing Bai, Changhui Zhou |
| Institutions | Shanghai Jiao Tong University, Shanghai Institute of Pollution Control and Ecological Security |
| Citations | 37 |
Abstract
Section titled āAbstractāUrine is a nitrogenous waste biomass but can be used as an appealing alternative substrate for H<sub>2</sub> recovery. However, urine electrolysis suffers from sluggish kinetics and requires alkaline condition. Herein, we report a novel system to decompose urine to H<sub>2</sub> and N<sub>2</sub> under neutral conditions mediated by Cl<sup>ā¢</sup> using oxygen-vacancy-rich Co<sub>3</sub>O<sub>4</sub> nanowire (O<sub>v</sub>-Co<sub>3</sub>O<sub>4</sub>) anodes and CuO nanowire cathodes. The Co<sup>2+</sup>/Co<sup>3+</sup> cycle in Co<sub>3</sub>O<sub>4</sub> activates Cl<sup>-</sup> in urine to Cl<sup>ā¢</sup>, which rapidly and selectively converts urea into N<sub>2</sub>. Thus, electron transfer is boosted for H<sub>2</sub> production, eliminating the kinetic limitations. The shuttle of Co<sup>2+</sup> to Co<sup>3+</sup> is the key step for Cl<sup>ā¢</sup> yield, which is accelerated due to the introduction of O<sub>v</sub>. Electrochemical analysis shows that O<sub>v</sub> induces positive charge on the Co center; therefore, Co<sup>2+</sup> loses electrons more efficiently to form Co<sup>3+</sup>. H<sub>2</sub> production in this system reaches 716 Ī¼mol h<sup>-1</sup>, which is 320% that of non-radical-mediated urine electrolysis. The utilization of O<sub>v</sub>-Co<sub>3</sub>O<sub>4</sub> further enhances H<sub>2</sub> generation, which is 490 and 210% those of noble Pt and RuO<sub>2</sub>, respectively. Moreover, urine is effectively degraded in 90 min with the total nitrogen removal of 95.4%, and N<sub>2</sub> is the final product. This work provides new insights for efficient and low-cost recovery of H<sub>2</sub> and urine remediation.