A Review of Non-Thermal Plasma Technology: A novel solution for CO2 conversion and utilization

Owing to the increasing emissions of carbon dioxide (CO(2)), human life and the ecological environment have been affected by global warming and climate changes. To mitigate the concentration of CO(2) in the atmosphere various strategies have been implemented such as separation, storage, and utilization of CO(2). Although it has been explored for many years, hydrogenation reaction, an important representative among chemical conversions of CO(2), offers challenging opportunities for sustainable development in energy and the environment. Indeed, the hydrogenation of CO(2) not only reduces the increasing CO(2) buildup but also produces fuels and chemicals. In this critical review we discuss recent developments in this area, with emphases on catalytic reactivity, reactor innovation, and reaction mechanism. We also provide an overview regarding the challenges and opportunities for future research in the field (319 references).

This paper reviews recent progress made in identifying electrocatalysts for carbon dioxide (CO2) reduction to produce low-carbon fuels, including CO, HCOOH/HCOO(-), CH2O, CH4, H2C2O4/HC2O4(-), C2H4, CH3OH, CH3CH2OH and others. The electrocatalysts are classified into several categories, including metals, metal alloys, metal oxides, metal complexes, polymers/clusters, enzymes and organic molecules. The catalyts' activity, product selectivity, Faradaic efficiency, catalytic stability and reduction mechanisms during CO2 electroreduction have received detailed treatment. In particular, we review the effects of electrode potential, solution-electrolyte type and composition, temperature, pressure, and other conditions on these catalyst properties. The challenges in achieving highly active and stable CO2 reduction electrocatalysts are analyzed, and several research directions for practical applications are proposed, with the aim of mitigating performance degradation, overcoming additional challenges, and facilitating research and development in this area.

Controlling the catalytic reduction of CO 2 by H 2 to produce CO, methanol or hydrocarbons requires stabilization of key reaction intermediates. Ocean acidification and climate change are expected to be two of the most difficult scientific challenges of the 21st century. Converting CO 2 into valuable chemicals and fuels is one of the most practical routes for reducing CO 2 emissions while fossil fuels continue to dominate the energy sector. Reducing CO 2 by H 2 using heterogeneous catalysis has been studied extensively, but there are still significant challenges in developing active, selective and stable catalysts suitable for large-scale commercialization. The catalytic reduction of CO 2 by H 2 can lead to the formation of three types of products: CO through the reverse water–gas shift (RWGS) reaction, methanol via selective hydrogenation, and hydrocarbons through combination of CO 2 reduction with Fischer–Tropsch (FT) reactions. Investigations into these routes reveal that the stabilization of key reaction intermediates is critically important for controlling catalytic selectivity. Furthermore, viability of these processes is contingent on the development of a CO 2 -free H 2 source on a large enough scale to significantly reduce CO 2 emissions.