CO2-rich and CO2-lean streams as activators of reducing metals for the green hydrogen generation and the catalytic production of formate

The ongoing pursuit of carbon mitigation and utilization encourages the study of common and more abundant materials, capable of facilitating the technical readiness of the processes involved. In this context, the present work aims at evaluating the CO2-rich and CO2-lean streams from the basic aqueous absorption CO2 capture processes, for the in-situ generation of green hydrogen through the metal-water splitting technology, to convert captured CO2 into formate. Experiments have been carried out using aluminum and zinc as reducing agents, and the commercial catalysts palladium, platinum and ruthenium supported on activated carbon, using a batch stirred reactor. Aluminum and Pd5AC constituted the best metal/catalyst system, with a formate yield of 22 %, selectivity of 32 %, and conversion of 67 %. The H2-TPR characterization of the catalysts, before and after reaction, showed that only Pd5AC catalyst shows insights of active hydride specie, responsible for the reduction of captured CO2. The in-situ hydrogen evolution was studied during prolonged 10 h experiments, in absence of catalyst, to compare the performance of the proposed basic streams and reducing metals, generating high reliability data in search for feasibility and future integration of CO2 and H2 economies.