Kinetics and Mechanisms of Reduction of Protons and Carbon Dioxide Catalyzed by Metal Complexes and Nanoparticles

Abstract

Kinetics and mechanisms of reduction of protons and CO2 catalyzed by metal complexes and nanoparticles have been discussed in this chapter. Kinetic studies including deuterium kinetic isotope effects on heterogeneous catalysts for hydrogen evolution by proton reduction have been demonstrated to provide essential mechanistic information on bond cleavage and formation associated with electron transfer. The rate-determining steps in the catalytic cycles are clarified by kinetic studies, providing valuable information on observable intermediates. The most important intermediates in the catalytic reduction of protons and CO2 are metal-hydride complexes, which can reduce protons and CO2 to produce hydrogen and formic acid, respectively. The catalytic interconversion between hydrogen and a hydrogen storage compound has been made possible by changing pH, providing a convenient hydrogen-on-demand system in which hydrogen gas can be stored as a liquid (e.g., formic acid) or solid form (NADH) and hydrogen can be produced by the catalytic decomposition of the hydrogen storage compound.