Enhanced electrocatalytic nitrate reduction to ammonia using plasma‐induced oxygen vacancies in CoTiO_3 − x nanofiber

Abstract

Electrochemical nitrate (NO3−) reduction is a green and economic route for ammonia (NH3) synthesis. However, this conversion suffers from low NH3 selectivity due to strong competition from other NO3− reduction pathways. Here, we report that a plasma‐induced defective CoTiO3 − x nanofiber with oxygen vacancies acts as an efficient electrocatalyst for NO3− reduction to NH3. In 0.1 M NaOH solution containing 0.1 M NO3−, it is capable of achieving a remarkable NH3 yield of 30.4 mg h–1 mgcat.–1 and a high Faradaic efficiency of 92.6%. The catalyst also shows strong electrochemical stability for a 20‐h electrolysis test. Additionally, a Zn‐NO3− battery using CoTiO3 − x as the cathode catalyst offers a peak power density of 5.04 mW cm−2 and a large NH3 yield of 3.08 mg h−1 mgcat.−1. The catalytic mechanism is further discussed by density functional theory calculations.

Recent progress and strategies on the design of catalysts for electrochemical ammonia synthesis from nitrate reduction

“…Recently, our group reported that CoTiO 3− x nanofibers with oxygen vacancies showed an NH 3 formation rate of 30.4 mg h −1 mg −1 and a large FE of 92.6% in 0.1 M NaOH solution containing 0.1 M NO 3 − . 136 The CuWO 4 hollow nanospheres with oxygen vacancies showed a high NH 3 FE of 94.6% and yield rate of 5.84 mg h −1 mg −1 at −0.7 V vs . RHE.…”

Recent achievements of free‐standing material and interface optimization in high‐energy‐density flexible lithium batteries

“…In general, active materials and conductive additives are tightly integrated into the flexible substrate with the assistance of inactive polymer binders among flexible electrodes. The commonly used flexible substrates are mainly divided into three types: carbonaceous materials (CMs), [ 25,26 ] polymer networks (PNs), [ 13,27 ] and modified metal [ 28,29 ] substrates (MMs). Based on the selected flexible substrate, the flexible electrodes could obtain specific properties such as conductivity, mechanical durability, and chemical stability.…”

“…In subsequent research, it was recognized that the flexible conductive substrate is a superior choice for FLBs because it can replace traditional current collectors, conductive additives, and even binders, reducing the portion of inactive materials and the amount of contact interface. For instance, conductive cellulose nanofiber‐based cathodes, [ 13 ] Ni‐cotton fabric‐based cathodes, [ 12 ] and Si/SiO x ‐based carbon fiber (CF) free‐standing anodes [ 15 ] have been developed.…”

“…Regarding the aforementioned issues, researchers have developed various flexible free‐standing components and flexible battery structures in recent years, such as flexible conductive substrates, [ 11–13 ] flexible free‐standing electrodes (FFEs), [ 14,15 ] and electrolyte materials. [ 16 ] In addition, the flexible structure batteries including one‐dimensional [ 1,17 ] (1D) wire‐shaped and three‐dimensional [ 18,19 ] (3D) interlocked configuration are further designed to make the LiBs flexible and wearable function.…”

“…Therefore, the FFEs with various structures (1D nanofiber, 2D film, and 3D network architecture electrodes) are constructed by the methods of electrospinning, [ 20 ] hydrothermal reaction, [ 21 ] vacuum filtration technology, [ 22 ] and others. [ 13,15 ] Moreover, the assembly of flexible lithium‐based batteries (FLBs) with FFEs shows excellent mechanical durability and high energy density, as well as can effectively restrain the adverse volume change of the anode. Meanwhile, flexible solid electrolytes (FSEs) are considered as pivotal contributors to ameliorate the safety and flexibility of FLBs because of their excellent thermodynamic stability and free bending.…”