Enhanced nitrate reduction with copper phthalocyanine-coated carbon nanotubes in a solid polymer electrolyte reactor

Research on nitrate removal has drawn more attention because of the increasing nitrate contamination in ground and surface water. In this work, copper phthalocyanine supported on functionalised multiwalled carbon nanotubes (CuPc/CNT) prepared using the impregnation method was characterised and tested for their electrocatalytic behaviour towards nitrate reduction. Cyclic voltammetry, rotating disc electrode and chronoamperometry techniques were employed for the electrochemical characterisation. The CuPc/CNT electrocatalyst showed higher catalytic activity towards nitrate reduction than CuPc supported on carbon black (CuPc/C). From kinetic studies, the order of reaction and the reaction rate constant were found to be 0.78, 15.03 and 0.81, 0.46 s −1 for CuPc/CNT and CuPc/C, respectively. Electrolysis studies in an H-cell at 24 h showed the percentage of nitrate removal up to 76 and 45 % for CuPc/CNT and CuPc/C, respectively. Furthermore, nitrate reduction in a solid polymer electrolyte reactor with membrane electrode assemblies designed using supported CuPc cathode showed a maximum faradaic efficiency of 41 % for CuPc/CNT and 38 % for CuPc/C. Graphical Abstract