Visualizing oscillating NiO appear and disappear on the surface of Ni@Au catalyst driven by a hybrid water-hydrogen atmosphere

In situ and operando TEM have paved the way in studying materials’ composition and structure down to atomic resolution in their working status. Among catalyzed gas reactions, water can act as both a reactant and a product, like in water-gas shift reactions (WGS) and reversed WGS. Water’s negative effects on metal corrosion and catalyst deactivation are also well-known and have been under study for decades. Insights into the role of water in catalytic reactions is important for unveiling reaction mechanisms, and thus critical for the optimization of the catalyst or for reaction recipes involving water. Despite the importance, the study of water’s influence on gas-solid reactions inside a TEM is limited. This is due to the lack of control over the flow rate and pressure of the water vapor, as well as the fear of contaminating the high-vacuum TEM columns