An integrated smartphone-based electrochemical detection system for highly sensitive and on-site detection of chemical oxygen demand by copper-cobalt bimetallic oxide-modified electrode.

A portable and integrated electrochemical detection system has been constructed for on-site and real-time detection of chemical oxygen demand (COD). The system mainly consists of four parts: (i) sensing electrode with a copper-cobalt bimetallic oxide (CuCoOx)-modified screen-printed electrode; (ii) an integrated electrochemical detector for the conversion, amplification, and transmission of weak signals; (iii) a smartphone installed with a self-developed Android application (APP) for issuing commands, receiving, and displaying detection results; and (iv) a 3D-printed microfluidic cell for the continuous input of water samples. Benefiting from the superior catalytic capability of CuCoOx, the developed system shows a high detection sensitivity with 0.335 µA/(mg/L) and a low detection limit of 5.957 mg/L for COD determination and possessing high anti-interference ability to chloride ions. Moreover, this system presents good consistency with the traditional dichromate method in COD detection of actual water samples. Due to the advantages of cost effectiveness, portability, and point-of-care testing, the system shows great potential for water quality monitoring, especially in resource-limited remote areas.

Synergistic contribution of metal-acid sites in selective hydrodeoxygenation of biomass derivatives over Cu/CoOx catalysts.

The efficient hydrodeoxygenation (HDO) of biomass derivatives to yield specific products is a significant yet challenging task. In the present study, a Cu/CoOx catalyst was synthesized using a facile co-precipitation method, and subsequently used for the HDO of biomass derivatives. Under optimal reaction conditions, the conversion of 5-hydroxymethylfurfural reached 100% with a selectivity of ∼99% to 2,5-diformylfuran. In combination with the experimental results, systematic characterizations revealed that CoOx, as the acid site, tended to adsorb CO bonds, and the metal sites of Cu+ were inclined to adsorb CO bonds and enhance CO bond hydrogenation. Meanwhile, Cu0 was the main active site for 2-propanol dehydrogenation. The excellent catalytic performance could be attributed to the synergistic effects of Cu and CoOx. Further, by optimizing the ratio of Cu to CoOx, the Cu/CoOx catalysts exhibited notable performance in HDO of acetophenone, levulinic acid, and furfural, which verified the universality of the catalysts in the HDO of biomass derivatives.