Remarkably efficient and stable Ni/Y2O3 catalysts for CO2 methanation: Effect of citric acid addition

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.

Net anthropogenic CO2 emissions must approach zero by mid-century to stabilize global mean temperature at the levels targeted by international efforts 1–5 . Yet continued expansion of fossil fuel energy infrastructure implies already ‘committed’ future CO2 emissions 6–13 . Here we use detailed datasets of current fossil fuel-burning energy infrastructure in 2018 to estimate regional and sectoral patterns of “committed” CO2 emissions, the sensitivity of such emissions to assumed operating lifetimes and schedules, and the economic value of associated infrastructure. We estimate that, if operated as historically, existing infrastructure will emit ~658 Gt CO2 (ranging from 226 to 1479 Gt CO2 depending on assumed lifetimes and utilization rates). More than half of these emissions are projected to come from the electricity sector, and infrastructure in China, the U.S.A., and the EU28 represent ~41%, ~9% and ~7% of the total, respectively. If built, proposed power plants (planned, permitted, or under construction) would emit an additional ~188 (37–427) Gt CO2. Committed emissions from existing and proposed energy infrastructure (~846 Gt CO2) thus represent more than the entire carbon budget to limit mean warming to 1.5 °C with 50–66% probability (420–580 Gt CO2) 5 , and perhaps two-thirds of the budget required to similarly limit warming to below 2 °C (1170–1500 Gt CO2) 5 . The remaining carbon budget estimates are varied and nuanced 14,15 , depending on the climate target and the availability of large-scale negative emissions 16 , Nevertheless, our emission estimates suggest that little or no additional CO2-emitting infrastructure can be commissioned, and that earlier than historical infrastructure retirements (or retrofits with carbon capture and storage technology) may be necessary, in order meet Paris climate agreement goals 17 . Based on asset value per ton of committed emissions, we estimate that the most cost-effective premature infrastructure retirements will be in the electricity and industry sectors, if non-emitting alternative technologies are available and affordable 4,18 .