Electrochemical sensing mechanism of ammonium ions over an Ag/TiO2 composite electrode modified by hematite

Shilin Zhang; Jinqing Hu; Sam Fong Yau Li; Hongxiu Lu; Gang Wang; Chang Lu; Muhammad Tariq Sarwar; Aidong Tang; Huaming Yang

doi:10.1039/d3cc00240c

Electrochemical sensing mechanism of ammonium ions over an Ag/TiO₂ composite electrode modified by hematite

Chem Commun (Camb). 2023 Feb 28;59(18):2636-2639. doi: 10.1039/d3cc00240c.

Authors

Shilin Zhang^{1

2

3

4

5}, Jinqing Hu², Sam Fong Yau Li^{4

5}, Hongxiu Lu², Gang Wang², Chang Lu², Muhammad Tariq Sarwar^{1

3

6}, Aidong Tang^{1

2

3

6}, Huaming Yang^{1

3

6}

Affiliations

¹ Engineering Research Center of Nano-Geomaterials of Ministry of Education, China University of Geosciences, Wuhan 430074, P. R. China. tangaidong@cug.edu.cn.
² College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, P. R. China.
³ Faculty of Materials Science and Chemistry, China University of Geosciences, Wuhan 430074, P. R. China.
⁴ Department of Chemistry National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.
⁵ NUS Environmental Research Institute, National University of Singapore, T-Lab Building, 5A Engineering Drive 1, Singapore 117411, Singapore.
⁶ Key Laboratory of Functional Geomaterials in China Nonmetallic Minerals Industry, China University of Geosciences, Wuhan 430074, P. R. China.

PMID: 36779275
DOI: 10.1039/d3cc00240c

Abstract

Here, we demonstrate a new electrochemical sensing mechanism of ammonium ions (NH₄⁺) involving a two-electron oxygen reduction reaction (ORR) and a hydrazine reaction. The NH₄⁺ are electrooxidized to hydrazine by H₂O₂ derived from the ORR over a self-supporting Ag/TiO₂ nanotube array composite electrode modified by hematite (Ag/Fe₂O₃/TNTs). The Ag/Fe₂O₃/TNT sensor exhibits a high sensitivity of 1876 µA mM^-1 cm^-2 with a detection limit of 0.18 µM under non-alkaline conditions, a short response time of 3 s, good reproducibility, and fine selectivity among various interferents, and is also successfully used in real water bodies to display high accuracy. Furthermore, this new mechanism has a certain universality in a range of Ag (main catalyst)/transition metal oxide (cocatalyst)/TNT sensing systems. This work offers a new design basis for the urgently needed electrochemical ammonia nitrogen sensors.