Probe of nanocatalysts in-action by ambient pressure photoelectron spectroscopy

Elucidation of a physicochemical process on nanocatalysts, especially under continuously evolving conditions, is often heavily tool-driven because of technical challenges. Recently, ambient pressure X-ray photoelectron spectroscopy (APXPS) emerges as an emerging photon-in-electron-out technique in in-situ/operando analysis by bridging the pressure-gap between conventional ultra-high vacuum (UHV) and near ambient or even close to operating conditions, rendering the advancement of XPS from a UHV-based technique to a versatile and powerful tool that enables the specific probe of numerous events taking place at the gas–solid, liquid–solid and liquid–gas nanoscale interfaces which are critical to nanocatalysis research. For example, APXPS probes information on catalytically active phase and reaction kinetics in nanocatalytic processes; details inside the electric double-layer at an electrolyte/electrode interface can now be accessed; more efficient nanocatalyst design can be achieved and energy transfer venues can be optimized. Here, we aim to critically review the recent advances in instrumentation and the probe of the gas–solid, liquid–solid, and gas–liquid nanoscale interfaces using APXPS-based methodologies, followed by putting forward an outlook of the development of APXPS as a rising in-situ/operando analytical means in surface science, nanocatalysis, nanoscience and materials science.