Electrochemically tuning Li1+xFePO4 for high oxidation state of rich Li+ toward highly sensitive detection of nitric oxide

Electrochemical sensors involves electrocatalysis, which greatly relies on the surface electronic state of an electrode but often tedious or complicated surface modification toward a specific reaction. Here a facile electrochemical method is presented for the first time to directly tune Li1 + xFePO4 for rich Li+ insertion to an elevated oxidation state for a highly sensitive nitric oxide (NO) sensor, in which the Li+-richest lithium iron phosphate (Li1.66FePO4, 7.3 wt%) over the pristine LiFePO4 (Li+ content of 4.5 wt%) is achieved, delivering a much higher sensitivity (90.38 vs 58.70 mu A cm(-2) mu M-1) and a lower limit of detection (0.12 vs 3.10 nM) than the latter. The enhancement mechanism is investigated, indicating that high Li+ insertion in LiFePO4 rises the surface electronic structure for high oxidation state to strongly adsorb electronegative NO molecules and kinetically prompt the fast electron transfer toward NO oxidation. Additionally, a Li1.66FePO4 modified screen printed electrode was designed and fabricated to directly grow cells as unique sensing platform, by which the cell-released NO could be immediately captured for in situ real-time detection. This direct electrochemical tuning strategy significantly enhances sensing performance to accomplish the highest sensitivity (649.2 mu A cm(-2) mu M-1) among all nonprecious material-based NO sensors while possessing universal significance to design various highly sensitive and selective electrochemical sensors. (c) 2020 Elsevier Ltd. All rights reserved.

Automated summary

A facile electrochemical method was introduced to tune Li1 + xFePO4 for a highly sensitive nitric oxide (NO) sensor, achieving higher sensitivity and lower detection limit compared to pristine LiFePO4. The enhanced performance is attributed to the high Li+ insertion in LiFePO4, which promotes the adsorption of NO molecules and fast electron transfer for NO oxidation. The direct electrochemical tuning strategy significantly improves sensing performance, making it the highest sensitivity NO sensor among all nonprecious material-based sensors.