Trends and advances in Operando methodology

Abstract

After the introduction of the term, operando, the catalysis community has taken significant steps forward to understand chemistry and physics taking place within catalyst body and catalytic reactor on different length and time scales with great motivation to firmly establish catalyst structure vs. catalytic performance relationships. Herein recent advances, current trends and possible future directions in operando methodology are briefly summarized.

Trends and Advances in the Characterization of Gas Sensing Materials Based on Semiconducting Oxides

“…Although many of these methods allow the study of well-defined systems, the obtained results are far from realistic conditions. This results in three major gaps between the experimental and realistic operation conditions, namely in material, pressure and temperature [ 21 ].…”

“…Nevertheless, for establishing structure-function-relationships is mandatory to obtain the anticipated information as close to real operation conditions as possible, to determine correctly obtained structures or identify active centers. For various functional materials, using so-called in-situ or operando methods is considered as state of the art approach for gaining insights in fundamental working principles [ 15 , 16 , 21 , 29 ]. In the early 2000s, various researchers in the field of catalysis coined the term operando.…”

“…The use of complementary techniques in a multi-probe-approach is commonly used for the investigations of various catalysts. The information might be recorded in separate experiments or at the same time [ 21 , 51 , 52 , 53 ]. For spectroscopic and other characterization techniques, the term ‘complementary’ includes techniques, which probe different properties, a similar kind of property or properties at different length or depth scales.…”

“…The challenge of identifying active species is well-known from catalysis research, since not all detected surface species contribute to the catalytic process and often correspond to slowly reacting or completely inactive spectators [ 21 , 67 , 68 , 69 ]. In the case of gas sensing, similar considerations can be made: Active species and processes change the concentration of surface charge as a result of changes in the atmosphere; Inactive species do not change the surface charge or are not involved in processes changing the surface charge.…”

Engineering operando methodology: Understanding catalysis in time and space

“…The operando methodology provides a direct grip between the working catalyst site structure and its performance. It has been evidenced as an invaluable tool to understand catalysis [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] and as method for real-time operation control [33]. The value of the operando methodology is that it characterizes a working catalyst and simultaneously measures its performance.…”