Ni(II)cyclam catalyzed reduction of CO2 -: Towards a voltammetric sensor for the gas phase

The detection Of CO2 in the gas phase is possible in presence of oxygen with an amalgamated Au-poly(tetrafluoroethylene) gas diffusion electrode and an internal electrolyte solution containing Ni(II)cyclam. For concentrations between 0.1 to 1 % the electrochemical cell has a sensitivity of 3.58 mA % (-1) and the detection limit is 500 ppm. In preliminary experiments at rotating disk electrodes the optimum pH-range was found to be between 3.5 to 6 and a selectivity ratio of the catalyst for CO2/H+ of 5:1 could be determined. The relationship between reduction current and the square root of the angular speed is linear, indicating that the electrochemical process is limited by diffusion of CO2. Tl and Pb are presented as alternative electrode materials at Which the Ni(II)cyclam catalyzed reduction Of CO2 can be observed. Problems arise from fouling effects at the sensing electrode and a non-linearity of the calibration plot at higher concentrations.