Recent Advances in Design of Gold-Based Catalysts for H2 Clean-Up Reactions

Abstract

Over the past three decades, supported gold nanoparticles have demonstrated outstanding properties and continue to attract the interest of the scientific community. Several books and comprehensive reviews as well as numerous papers cover a variety of fundamental and applied aspects specific to gold-based catalyst synthesis, characterization by different techniques, relationship among catalyst support features, electronic and structural properties of gold particles, and catalytic activity, reaction mechanism, and theoretical modeling. Among the Au-catalyzed reactions targeting environmental protection and sustainable energy applications, particular attention is paid to pure hydrogen production. The increasing demands for high-purity hydrogen for fuel cell systems caused a renewed interest in the water–gas shift reaction. This well-known industrial process provides an attractive way for hydrogen generation and additional increase of its concentration in the gas mixtures obtained by processes utilizing coal, petroleum, or biomass resources. An effective step for further elimination of CO traces from the reformate stream after water–gas shift unit is the preferential CO oxidation. Developing highly active, stable, and selective catalysts for these two reactions is of primary importance for efficient upgrading of hydrogen purity in fuel cell applications. This review aims to extend the existing knowledge and understanding of the properties of gold-based catalysts for H 2 clean-up reactions. In particular, new approaches and strategies for design of high-performing and cost-effective formulations are addressed. Emphasis is placed on efforts to explore appropriate and economically viable supports with complex composition prepared by various synthesis procedures. Relevance of ceria application as a support for new-generation WGS catalysts is pointed out. The role of the nature of support in catalyst behavior and specifically the existence of an active gold–support interface is highlighted. Long-term stability and tolerance toward start-up/shutdown cycling are discussed. Very recent advances in catalyst design are described focusing on structured catalysts and microchannel reactors. The latest mechanistic aspects of the water–gas shift reaction and preferential CO oxidation over gold-based catalysts from density functional theory calculations are noted because of their essential role in discovering novel highly efficient catalysts.

Improved Water–Gas Shift Performance of Au/NiAl LDHs Nanostructured Catalysts via CeO2 Addition

“…Amid WGS catalysts, the supported gold ones have played a key role for more than three decades [ 10 , 11 , 12 , 13 , 14 , 15 ]. Because of their unique features, such as stability in oxidizing surroundings, non-pyrophority, no need of additional activation pre-treatment, appreciable WGS activity and specific electronic and structural peculiarity, these catalytic formulations have proven to be among the most auspicious options to replace the conventional WGS catalysts for small-scale applications in the low-temperature range (180–260 °C).…”

“…After that, many efforts have been focused on the elucidation of the effect of ceria and ceria-doped oxides on WGS performance of gold catalysts depending on the ceria particle size, surface area, surface structure, presence of dopants, etc. [ 10 , 15 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 ].…”

Comparative Catalytic Properties of Supported and Encapsulated Gold Nanoparticles in Homocoupling Reactions

“…Nanoscale colloidal metal particles can possibly serve as quasi-homogeneous catalysts to overcome common pitfalls (e.g., recyclability and reactivity) of homogeneous and heterogeneous catalytic systems (Astruc et al, 2005;Prati and Villa, 2013;Price et al, 2019). Among the many metal-based colloidal systems, gold nanoparticles (AuNPs) have shown great potential in fulfilling the need for quasi-homogeneous catalytic properties for several reasons: they have relatively easy-to-control structural features (e.g., size and shape), inherent biocompatible characteristics, and a reasonably high stability when properly modified (Cortie and van der Lingen, 2002;Corma and Garcia, 2008;Piella et al, 2016;Parmentier et al, 2018;Carabineiro, 2019;Tabakova, 2019;Jang et al, 2020). In addition, simple wet chemical synthetic approaches can readily allow for designing structurally diverse colloidal AuNPs possessing these advantages to serve as effective catalysts, even under green reaction conditions.…”

One-Step Synthesis of AuCu/TiO2 Catalysts for CO Preferential Oxidation

“…Au nanoparticles supported on TiO 2 (Au/TiO 2 catalyst) showed good CO conversions and CO 2 selectivity for CO-PROX reaction in the range of 20 to 100 o C; however, the procedure used to prepare Au/TiO 2 catalysts has a significant influence on the catalytic performance, which is a result of Au nanoparticles sizes (should be smaller than 5 nm) and Au-TiO 2 interactions [6][7][8][9][10][11][12] . Sangeetha et al 13 prepared Au nanoparticles supported on CuO x -TiO 2 (x from 1 and 10 wt%), where the support was prepared by impregnation of Cu(NO 3 ) 2 in TiO 2 (Degussa P25) and treating at 350ºC.…”