Nitrogen doping and titanium vacancies synergistically promote CO 2 fixation in seawater

• Published in: Nanoscale 2020-08, Vol.12 (33), p.17191-17195
• Main Authors: Qu, Di, Peng, Xianyun, Mi, Yuying, Bao, Haihong, Zhao, Shunzheng, Liu, Xijun, Luo, Jun
• Format: Article
• Language: English
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/D0NR03775C

The electrocatalytic generation of useful chemicals from CO 2 , H 2 O, and sustainable energy resources offers a promising strategy for the carbon cycle. However, the current CO 2 electrolysis system is mainly operated in artificial electrolytes ( e.g. ionic liquids and inorganic salt solutions), of which the high cost and impractical working conditions hinder its large-scale development. In this case, seawater represents an attractive alternative due to its abundance and good conductivity. Herein, we show that N-doping and titanium vacancies (V Ti ) can be introduced in Ti 3 C 2 MXene nanosheets via a facile NH 3 -etching pyrolysis approach. These nanosheets demonstrate impressive CO 2 reduction reaction (CO 2 RR) performances in seawater with a remarkable 92% faradaic efficiency and a partial current density of −16.2 mA cm −2 for CO production, being close to those of noble metal electrodes. Mechanistic studies reveal that the existence of N dopants and V Ti synergistically modulates the electronic structure of the active Ti site, on which the free energy barriers for the key *COOH formation and desorption of *CO are greatly reduced, thereby leading to a notable CO 2 RR improvement. This study provides an opportunity for developing an active and cost-effective CO 2 electrolysis system by using seawater as the electrolyte.