Graphene oxide-manganese oxide composite as an electrocatalyst for simultaneous detection of manganese- and chromium-contaminated water

The development of a sensitive and selective electrochemical sensor for simultaneous quantification of manganese (Mn(II)) and chromium (Cr(VI)) using composite of graphene oxide (GO) and manganese oxide modified screen printed carbon electrode (GO-Mn₂O₃/SPCE) is reported for the first time. The good sensing performance is achieved by mixing GO prepared by modified Hummer's method (GO-H) with proper particle size of Mn₂O₃ (241 nm). The mechanism of this sensor is based on the formation of Mn-O and Cr-O on the modified electrode with assistance of oxygen moieties provided by both Mn₂O₃ NPs and GO. The analytical performances were investigated by measuring electrochemical signal of Mn(II) and Cr(VI) by using square-wave cathodic stripping voltammetry (SWCSV). This sensor holds low electrode-to-electrode variation (relative standard deviation (RSD) < 4%) with a good limit of detection (LOD) at about 6.67 and 11.20 μg⋅L^-1 for Mn(II) and Cr(VI), respectively. Applicability of this sensor was demonstrated by measuring Mn(II) and Cr(VI) in tap water samples with recovery of 90.77-103.45% and 82.34-103.73% for Mn(II) and Cr(VI) determinations, respectively. With the contribution of both GO and Mn₂O₃ as electrocatalysts, this developed sensor is capable to be used for water quality monitoring in real samples.