Diamond with Unexpected Multi-Scale Pores.

Following the diverse structural characteristics and primary usage, diamond products include nano-polycrystalline diamond (NPD), micron-polycrystalline diamond (MPD), diamond film, porous diamond, and diamond wire drawing die. Among them, porous diamond possesses a distinctive combination of flexible surface functionality and a remarkably high surface area-to-volume ratio (SA/V) compared to traditional bulk materials, which contributes to cross-cutting applications in catalysis, adsorption, and electrochemistry while retaining the superior traits of diamond, particularly its exceptional chemical inertia. To avoid etching or microwave plasma chemical vapor deposition (MPCVD) techniques, this study proposes a high-temperature and high-pressure method based on a soluble skeleton (HPHT-ss) as an efficient and inexpensive approach for synthesizing millimeter-level porous diamonds. Interestingly, porous diamond synthesized by HPHT-ss exhibits multiscale pores distributed as macropores (average 75 µm) and mesopores (average 19 nm), which gives it a unique feature compared with other methods. Pertinent temperature-pressure conditions, HPHT-ss synthesis, and the formation mechanism of porous diamonds are also thoroughly discussed.