AFM Materials Journal Club

PeakForce EC-AFM to Visualize In Operando, Real-Time Evolution of NiOxHy Nanosheet

by Jiang Deng, Michael R. Nellist, Michaela Burke Stevens, Christian Dette, Yong Wang, and Shannon W. Boettcher

Nano Lett., 2017, 17 (11), pp 6922–6926

Nickel (oxy) hydroxide-based (NiOxHy) composites are very important materials in energy conversion and storage systems, such as pseudosupercapacitors, alkaline batteries and solar fuel devices. Both the initial conditioning and the metal impurities in the surrounding electrolytes have critical impacts on device performance. This work employs in-situ PeakForce electrochemical AFM to investigate dynamic changes of a single-layered Ni(OH)₂ nanosheet resulting from electrochemical testing. PeakForce Tapping is a gentle, stable, and off-resonance tapping mode that serves as a highly-desired, convenient technique for imaging dynamic processes in liquid. The authors quantified dynamic changes through depth histograms, mean heights, surface areas, and volumes, captured by AFM. Their research demonstrates the initial activation process in pseudosupercapacitors and batteries that results from the increase of volume and effective surface. The authors also show how iron cation incorporates into the nanosheet and expands the NiOxHy materials. This publication well visualizes the dynamic nature of NiOxHy-based materials during electrochemistry measurements. These new findings are important for the fundamental understanding of NiOxHy-based energy devices.