A fiber-optic sensor for in-situ detection of methanol production rate in photocatalytic CO2 reduction reaction

In the pursuit of achieving in-situ real-time detection of methanol production rate during the photocatalytic reduction of CO₂, we developed a methanol sensor using a copolymer-coated fiber Bragg gratings. The theoretical model of methanol measurement by sensor was established. The effect of methanol-selective sensitive material and its thickness on the performance of the sensor were investigated. Humidity and temperature interference to sensor measurements was compensated. Furthermore, TiO₂ photocatalyst was prepared and the photocatalytic reactor was constructed. The methanol production rate in the photocatalytic CO₂ reduction process was monitored by the prepared sensor in-situ. The results highlight that the fiber Bragg grating methanol sensor with 600 nm-thick poly(N-isopropylacrylamide)/polymethyl-methacrylate coating showed a high sensitivity, lower limit of detection, fast response and recovery speed, and high selectivity. The methanol generation rate of TiO₂ photocatalytic reduction of CO₂ measured by gas chromatograph and prepared fiber Bragg grating methanol sensor was 1.42 and 1.53 μmol/g-cat·h, respectively, the error of the two detection methods was 7.86%. This highlights the efficacy of the developed fiber Bragg grating methanol sensor for real-time in-situ detection of the methanol production rate during the photocatalytic reduction of CO₂.