Composites of porous carbon and copper-based nanoparticles for the electrochemical analysis of chemical oxygen demand

The intensive monitoring of water quality enforced by new wastewater regulations calls for the developing of fast and low-cost analytical technologies. Electrochemical sensors are poised to become alternative technologies for the sensitive analysis of environmentally relevant chemicals. A prerequisite for this evolution is engineering analyte-specific electrodes which are easily processed and can be mass-produced. This work studies different routes to prepare composites comprising a porous carbon matrix with Cu or Cu2O nanoparticles as electrodes to analyze chemical oxygen demand (COD) in wastewaters. The materials were prepared by physical mixing of the two components and one-pot chemical synthesis, characterizing their microstructure, porosity, nanoparticle distribution, and crystallinity. Then, their analytical performance was assessed by measuring glucose as a standard analyte and testing three real samples from a wastewater treatment plant. While all the materials performed well in the COD analysis, in excellent agreement with those obtained by the standard dichromate method, a one-pot synthesis approach stands out for its ease of production and analytical response. This one-step liquid processing is scalable and compatible with the industrial manufacturing of electrochemical sensors of planar configuration by screen-printing or microfabrication techniques.This work was partially funded by Generalitat de Catalunya, grants numbers 2017 SGR 1771 and 2017 SGR 765 and the Spanish Ministry of Science and Innovation through the Severo Ochoa Programme for Centers of Excellence in R&D (CEX2019-000917-S). We are very grateful to Antoni Baldi, Mercè Baldi and Josefina Torán for their help and for kindly providing us with the real water samples. The Chinese Scholarship Council fellowship (201806220063) to WD is also acknowledged. The Spanish Ministry of Education, Culture and Sport is funding the FPU Fellow of MT (FPU16/05452). WD and MT are enrolled in the Materials Science PhD Program of the UAB (Universitat Autònoma de Barcelona). The X-ray diffraction and thermal analysis laboratories of the ICMAB scientific services contributed to this work and are acknowledged. This work used the Spanish ICTS Network MICRONANOFABS that was partly supported by the Spanish Ministry of Science and Innovation.With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).Peer reviewe