Atomically dispersed nickel in CeO2 aerogel catalysts completely suppresses methanation in the water-gas shift reaction

Abstract

Nickel-based catalysts are widely studied for water-gas shift (WGS), a key intermediate step in hydrogen production from carbon-based feedstocks. Their viability under practical conditions is limited at high temperatures when Ni aggregates and converts CO to methane, an undesirable side product. Because experimental and computational studies identify undercoordinated Ni step sites as most active toward CH₄ formation, we eliminate Ni step sites by atomically dispersing Ni into networked, nanoparticulate CeO₂ aerogels. The mesoporous catalyst with 2.5 atomic % Ni in CeO₂ is highly active for WGS, converting near-equilibrium levels of CO at 350°C, while no CH₄ is detected at the limit of detection (<2 parts per million). In contrast, supporting low weight percentages of Ni clusters or nanoparticles on CeO₂ aerogels leads to methanation. The CH₄ yield produced by the atomically dispersed Ni-substituted CeO₂ aerogel is over an order of magnitude lower than previously reported Ni-based catalysts claiming methane suppression, marking an important advance in the development of WGS catalysts.