Recycling cobalt in spent lithium-ion batteries for synthesizing the hierarchically porous Co-Co3O4@NC-CNT microspheres: Toward efficient glucose and hydrogen peroxide electrochemical sensors

Non-noble-metal nanomaterials, characterizing by their low cost, large surface area, abundant active sites, and superior conductivity, play a pivotal role in the development of advanced electrochemical sensors. In this study, cobalt oxalates recovered from waste lithium-ion batteries are employed as cobalt sources to successfully synthesize three-dimensional (3D) porous Co-Co 3 O 4 @NC-CNT microspheres via a straightforward hydrothermal method. The sensors based on Co-Co 3 O 4 @NC-CNT microspheres enable rapid, sensitive, and precise detection of hydrogen peroxide (H 2 O 2 ) and glucose. Under optimum conditions, when used for glucose detection, the Co-Co 3 O 4 @NC-CNT microspheres exhibit a rapid response time of 2.9 s, a low limit of detection (LOD = 0.066 μM), a high sensitivity of 104.73 μA cm −2  mM −1 , and a wide linear range of 0.01 to 16.0 mM. For H 2 O 2 detection, the 3D porous Co-Co 3 O 4 @NC-CNT microspheres demonstrate an excellent sensitivity of 238.74 μA cm −2  mM −1 , a low LOD of 0.128 μM, and a wide linear range of 0.04 to 16.0 mM. In addition, as non-enzymatic sensors for both glucose and H 2 O 2 , the 3D porous Co-Co 3 O 4 @NC-CNT microspheres showcase exceptional stability, repeatability, and remarkable resistance to interference from organic and inorganic molecules. Notably, the electrochemical sensors based on Co-Co 3 O 4 @NC-CNT microspheres demonstrate excellent accuracy in the quantitative determination of H 2 O 2 and glucose concentrations in real samples. This study not only establishes a promising industrial chain for the recycling of cobalt from spent devices to synthesize 3D porous and spherical Co-Co 3 O 4 @NC-CNT catalysts, but also paves the way for the sensitive and rapid detection of H 2 O 2 and glucose concentrations in real samples, along with other biosensing applications.