Photocatalytic fuel cell self-powered sensor for Cu2+ detection in water and soil: Signal amplification of biomass induced carbon-rich carbon nitride photoanode

The development of an accurate, selective, sensitive, and quantitative monitoring method for copper ion (Cu2+) in water and soil is crucial for addressing environmental pollution. Herein, a photocatalytic fuel cell self-powered sensor (PFC-SPS) platform was proposed by carbon-rich carbon nitride photoanode for Cu2+ determination. Carbon-rich carbon nitride is formed by replacing nitrogen atoms of tertiary nitrogen with carbon generated through the thermal decomposition of biomass chitosan. The carbon-rich structure enhances the π delocalization in the carbon nitride skeleton, improving the optical absorption and accelerating the transmission of charge, endowing the photoanode with high and stable output signal. The formed Cu2+-aptamer complex increases the surface resistance of electrode, hindering the catalytic reaction of H2O2 oxidation and leading to the decrease in the output power density signal. This PFC-SPS platform detected Cu2+ with a wide range of 1.0 ∼ 1.5 × 103 nM, a low limit of 0.40 nM, excellent selectivity, stability and accuracy for real river water and agricultural soil samples. It is expected that the platform can achieve low-cost and portable monitoring by a digital multimeter, and this work also proposes a strategy for detecting heavy metal ions based on the synergism of a photocatalytic fuel and self-powered platform.