Oxygen reduction is a fundamental process involved in biological oxygen metabolism and also plays an important role in energy conversion such as fuel cells and metal/air batteries. Carbon dioxide fixation, including the conversion to carbonate and the reduction to other carbon sources, is significant in biology, energy and environmental sciences. Our research focuses on studying the basic reaction mechanisms involved in these processes by using molecular complexes developed in the lab. By providing crucial information to better understand the activation of these small molecules, we aim to obtain new catalyst systems with more efficiency and better selectivity.