Humidity sensing based strategy for in situ probing and manipulating electrified interfacial water adsorption dynamics

• An atomic engineering strategy was reported to tune the the humidity sensing performance of Mo 2 TiC 2. • An ultrahigh sensitivity of 1.75 was achieved on Mo 2 TiC 2 toward humidity sensing. • We report a strategy to explore the adsorption dynamics of electrified interfacial water. Understanding and manipulating the ubiquitous electrified interfacial water adsorption dynamics are highly important in surface science, sensing, catalysis and energy storage. However, the interfacial water is extremely hard to probe due to the interference from bulk water and complex interfacial environments. Herein we report a strategy to explore the adsorption dynamics of electrified interfacial water through combing a dynamic humidity sensing system, the in situ diffuse reflectance infrared Fourier transform spectroscopy, and the density functional theory calculations. By atomically engineering the Ti 3 C 2 T x with atomic Mo substitution of Ti, the water adsorption dynamics on the obtained Mo 2 TiC 2 T x were dramatically enhanced. The Mo 2 TiC 2 T x was demonstrated as an excellent humidity-sensing material with an ultrahigh sensitivity of 1.75±0.06, fast response (35.9 s) and hysteresis-free properties in 2.7-93% relative humidity range. This work provides universal strategies to in situ probe and manipulate the electrified interfacial water adsorption dynamics.