Atomic Layer Deposition of Noble Metal Nanoparticles for Catalytic Applications

Platinum group metals such as Pt, Ru, Pd, Ir, etc., have superior performance for various catalytic applications.^[1] Due to their scarcity, efforts were being made to reduce or replace these noble metals. Atomic Layer Deposition (ALD) is one among the best technique to facilitate lowering of loading mass on a support of interest.^[2],[3] Furthermore, ALD is the most suitable technology that can decorate high aspect ratio and high surface area substrate architectures.^[4] Due to the governing surface energy variations between noble metals and support surfaces, the growth initiates as nanoparticles (NP) and with a further increase in ALD cycles the agglomeration among NP’s dominates over the individual NP size increase, thus developing thin films of relatively higher thickness. The surface energy variations are also known to increase the nucleation delay of noble metals especially for Ru considerably. In this regard our efforts were laid to improve the functionality with pretreatments on carbonaceous supports which were shown promising to reduce the nucleation delay of ALD deposited Ru.<br/>For electrocatalytic applications, it is important to choose the right substrates. Among available substrates, carbon papers (CP) and titania nanotube (TNT) layers are best choices considering their physio-chemical properties, availability, vast literature, and low costs incurred using these as support substrates in electrocatalysis and photocatalysis. Several surface modifications for CP’s and variations on morphological aspects of TNT layers had received a great attention form applied fields due to their improved surface area, conductivity and stability.^[5]–[8] Uniformly decorating these CP’s and TNT layers by NPs or thin films of catalysts proved to be highly efficient with no boundaries on applications.^[9]<br/>The presentation will introduce and describe the synthesis of different noble metal NPs by ALD on various aspect ratio TNT layers and CP substrates. It will also include the corresponding physical and electrochemical characterization and encouraging results obtained in electrocatalysis.<br/>References<br/>Huang, Z. F. <i>et al.</i> <i>Advanced Energy Materials</i> vol. 7 (2017) 1700544.<br/>Yoo, J. E. <i>et al.</i> <i>Electrochem. commun.</i> <b>86</b>, (2018) 6<br/>Anitha, V. C. <i>et al.</i> <i>J. Catal.</i> <b>365</b>, (2018) 86.<br/>Zazpe, R. <i>et al.</i> <i>Langmuir</i> <b>32</b>, (2016) 10551.<br/>Sopha, H. <i>et al.</i> <i>Appl. Mater. Today</i> <b>9</b>, (2017) 104.<br/>Macak, J. M., Zlamal, M., Krysa, J. & Schmuki, P. <i>Small</i> <b>3</b>, (2007) 300.<br/>Liu, C., Sun, C., Gao, Y., Lan, W. & Chen, S. <i>ACS Omega</i> <b>6</b>, (2021) 19153.<br/>Sitaramanjaneya M. Thalluri & Macak, J. M. <i>Small <b>19</b> </i><i>(2023) </i>2300974<i>.</i><br/>Dvorak, F. <i>et al.</i> <i>Appl. Mater. Today</i> <b>14</b>, (2019) 1.