Direct instrumental identification of catalytically active surface sites

• Published in: Nature (London) 2017-09, Vol.549 (7670), p.74-77
• Main Authors: Pfisterer, Jonas H. K., Liang, Yunchang, Schneider, Oliver, Bandarenka, Aliaksandr S.
• Format: Article
• Language: English
• Subjects: 639/301/930/328/968; 639/638/77/886; 639/766/119/544; Catalysis; Catalysts; Catalytic activity; Chemical reduction; Chemical research; Defects; Electrocatalysts; Electrochemical reactions; Electrochemistry; Electrodes; Electrolytes; Electronic structure; Gold; Humanities and Social Sciences; Hydrogen; Hydrogen evolution reactions; Intermediates; letter; Microscopy; multidisciplinary; Noise; Oxygen; Science; Single crystals; Spatial resolution; Surface reactions
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature23661

Scanning tunnelling microscopy is used to distinguish between different active sites of a catalyst—such as boundaries between different materials—during a reaction, allowing the contributions of these sites to be evaluated. Identifying active catalyst sites Heterogeneous catalysts are crucial in the chemical and energy industries. Their activity is determined by specific sites that control the conversion of reactant molecules into product molecules. But the direct identification and monitoring of these sites during reactions is challenging. Jonas Pfisterer et al . now show that this is readily achieved using widely available scanning tunnelling microscopes by monitoring changes in the noise level during measurement. The data they collect enables the authors to distinguish between active sites, such as different defect sites and sites at the boundary between different materials comprising the catalyst, in an almost quantitative fashion. This information makes it possible to directly evaluate the importance and relative contribution of different sites to overall catalyst activity, which can directly feed into the rational design and optimization of heterogeneous catalysts targeted for a wide range of practical applications. The activity of heterogeneous catalysts—which are involved in some 80 per cent of processes in the chemical and energy industries—is determined by the electronic structure of specific surface sites that offer optimal binding of reaction intermediates. Directly identifying and monitoring these sites during a reaction should therefore provide insight that might aid the targeted development of heterogeneous catalysts and electrocatalysts (those that participate in electrochemical reactions) for practical applications. The invention of the scanning tunnelling microscope (STM) 1 , 2 and the electrochemical STM 3 , 4 promised to deliver such imaging capabilities, and both have indeed contributed greatly to our atomistic understanding of heterogeneous catalysis 5 , 6 , 7 , 8 . But although the STM has been used to probe and initiate surface reactions 9 , 10 , and has even enabled local measurements of reactivity in some systems 11 , 12 , 13 , it is not generally thought to be suited to the direct identification of catalytically active surface sites under reaction conditions. Here we demonstrate, however, that common STMs can readily map the catalytic activity of surfaces with high spatial resolution: we show that by monitoring relative changes i