Development of a membrane-cell for in situ NAP-XPS characterization

Octobre 2022 - Mars 2027

Partenaire IMN du projet : Marie-Paule BESLAND  (équipe PCM)

Coordinateur :
Institut de Recherches sur la Catalyse et l'Environnement de Lyon (IRCELYON)
Partenaires :
Laboratoire de Mécanique des Fluides et d'Acoustique (LMFA)
CRYOSCAN

Personnels IMN impliqués :
Marie-Paule BESLAND (DR CNRS), Valérie BRIEN (CR CNRS), Agnès GRANIER (DR CNRS), Pierre-Yves JOUAN (PR UNIV), Mireille RICHARD-PLOUET (DR CNRS)

---

Heterogeneous photocatalysis offers the promise of powering critical chemical processes with highly abundant, ubiquitous, and renewable solar energy. In particular photocatalytic conversion of small molecules such as H₂O, CO₂, or more recently N₂ into valuable fuels or chemical commodities has been the focus of an ever-increasing research effort for the past few decades. However, while significant progress has been made in photocatalyst design, there are still significant knowledge gaps in the understanding of catalyst active sites under operando conditions. Notably, UHV (ultra-high vacuum) - XPS (X-ray Photoelectron Spectroscopy) has been used to study the active phase in catalysis, but its operation is restricted to the ante-mortem and post-mortem examination of catalysts, under conditions irrelevant to actual catalytic conditions. As such, developing Near Ambient Pressure (NAP) XPS will allow to bridge the gap between the kinetic performances of catalysts and molecular reactions under in situ conditions. Nowadays, commercial NAP-XPS is presented as an alternative. However, regardless of the manufacturer SCIENTA or SPECS, commercial NAP-XPS requires an expensive differential pumping system to increase the photo-electrons count rates in the context of signal attenuation by the gas phase.

Here, we propose to develop a 2D membrane-cell device (NACELL, see Figure 1a) to carry out an operando XPS study on plasmonic photocatalytic thin films made of earth-abundant titanium oxynitride (TiO_xN_y) coated with Au and Cu nanoparticles (NPs) for the gas phase photocatalytic reduction of CO₂. Taking inspiration from natural photosynthesis, a photocatalytic gas-phase CO₂ reduction as a strategy to combine atmospheric CO₂ level mitigation with solar fuel generation. While a lot of work involve CO₂ bubbling through a photocatalyst suspension in water, recent studies have shown the possibility of flowing humid CO₂ at the surface of an illuminated photocatalyst Au NPs/TiO_xN_y decorated with an electrocatalyst such as Cu (used as-cocatalyst) NPs to generate CO or CH₄, thereby removing the need for the inefficient dissolution of CO₂ in water. Furthermore, depositing calibrated silver or gold NPs at the surface of photocatalysts can generate a well-known plasmonic effect, leading to enhanced light absorption and photocatalytic performance (Figure 1b). This strategy has recently been successfully employed to improve photocatalytic performance for the gas-phase CO₂ reduction to CO using water as an electron donor, achieving a CO production rate of more than 600 μmol.g^-1.h^-1 at the surface of an illuminated p-GaN/Al₂O₃/Au/Cu photocatalyst. For this, a dedicated cell will be designed and engineered, and experimental protocols for the routine characterization of photocatalytic materials will be developed (Figure 1).