Nanodiamonds (NDs) are increasingly being studied as semiconductors for photocatalysis, thanks in particular to the very specific positions of their valence and conduction bands, which can be modulated. For example, it has recently been shown that NDs can produce hydrogen under sunlight with an efficiency similar to that of TiO2 nanoparticles. Other studies also show the possibility of photogenerating solvated electrons from certain NDs for CO2 reduction or the degradation of stubborn pollutants.

With a view to accelerating the development of nanodiamond-based ‘solar-to-X’ technologies, we propose in this thesis to integrate nanodiamonds as photocatalysts in a sonophotocatalytic approach. Acoustic cavitation, generated by ultrasound, can improve mass transfer by dispersing catalytic particles and can produce additional reactive species (hydroxyl radicals, superoxides). It also emits sonoluminescence, which can promote the photogeneration of charges and should limit the recombination of charge carriers.

The first phase of the work will focus on the synthesis of nanodiamond-based photocatalysts, exploring various surface chemistries and their association with co-catalysts. Both classical and sonochemical synthesis methods will be used, as preliminary studies have shown that sonochemistry can effectively modify the surface chemistry of NDs. The photocatalytic properties of these materials will first be evaluated, leading to the design of a sonophotocatalytic cell. Further studies will explore the synergies between sonochemistry and photocatalysis for hydrogen production or CO2 reduction. This thesis will be carried out as part of a collaboration between the NIMBE at the Saclay CEA centre and the ICSM at the Marcoule CEA centre.