Octa-substituted metallophthalocyanines as heterogeneous catalysts for electrochemical reduction of carbon dioxide

One approach to address climate change is to electrochemically reduce CO2 to valuable products, but it requires suitable catalysts. In Chapter 2, solution processable alpha-position octa-substituted cobalt phthalocyanines (CoPc) using n-butoxy, sec-butoxy, and 2-ethylhexoxy substituents (having a similar electronic impact) were synthesized. In-solution aggregation of octa(2-ethylhexoxy)CoPc caused performance loss when drop-casted on the electrode's surface. Between octa(n-butoxy) and sec-butoxy CoPcs, the n-butoxy-substituted system showed superior catalytic current in lower loadings while the sec-butoxy system showed highest kinetics. Chapter 3 compares the electron rich octa(n-butoxy)CuPc and the electron deficient copper tetrapyrazino-porphyrazine (CuPyz) for CO2 reduction catalysis. CuPyz, with its electron deficient ring, was able to reduce CO2 more easily at more positive potentials, but it comes at the cost that CO2 binds less strongly to CuPyz than CuPcs. Different techniques were used to identify the CO2 reduction products; the CoPc systems make CO exclusively, but the products of the Cu-based catalysts could not be determined.