Multi-enzyme cascade in carbon dioxide electroreduction fuel cell

Abstract

Carbon neutrality can be facilitated by electroreduction of CO2 to access methanol using a surface with appropriate active sites to attain a stable Faradaic efficiency and partial current density to achieve an impressive transformation in a fuel cell. The 6H+/6e− electroreduction of CO2 affords methanol, however, challenging at high temperatures due to the uncontrollable formation and adsorption kinetics of CO instead of methanol. Therefore, a ‘kill three birds with a single stone’ can be achieved by an approach of a strategy that enables access to multiple types of dehydrogenase enzyme in a single system which brings the concept of the multi-enzyme cascade. A series of enzymes, formate dehydrogenase, formaldehyde dehydrogenase, and alcohol dehydrogenase require energy from equimolar cofactor nicotinamide adenine dinucleotide phosphate oxidation to nicotinamide adenine dinucleaotide+ (NAD+). Considering the hurdles of developing robust enzyme-immobilized electrodes and in situ reductions of NAD+, potentials of electroenzymatic and photoelectrochemical versions are reviewed, including effective recycling of NAD+. Co-immobilization of multi-enzymes into a hybrid matrix of conductive nanoarchitecture were discussed including various nicotinamide adenine dinucleotide phosphate regeneration and recycling features along with the controlled formation of the encapsulating cage of dehydrogenases. The rate of the formation of methanol is faster with co-immobilized enzymes. Co-immobilization of dehydrogenase is associated with NAD regeneration which involves (i) semiconductors or metals using solar illumination and (ii) reduction of NAD+ under electrochemical conditions. We have compared electroenzymatic and solar-driven electroenzymatic routes. This article depicts the need for electrochemical cells for enzyme cascade electrodes and their salient features. We have emphasized how lowering of over potential and maximizing Faradaic efficiency of CO2 electroreduction helps solve energy and environmental issues.