Co-doped hydroxyapatite as photothermal catalyst for selective CO2 hydrogenation

• Published in: Applied catalysis. B, Environmental Vol. 333; p. 122790
• Main Authors: Peng, Yong, Szalad, Horatiu, Nikacevic, Pavle, Gorni, Giulio, Goberna, Sara, Simonelli, Laura, Albero, Josep, López, Núria, García, Hermenegildo
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.09.2023
• Subjects: CO2 reduction; Hydroxyapatite; Localized metal surface plasmon resonance; Metal doping; Photothermal catalysis; Visible light; Visible light; Hydroxyapatite; Localized metal surface plasmon resonance; Photothermal catalysis; CO2 reduction; Metal doping
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2023.122790

The rational design and in deep understanding of efficient, affordable and stable materials to promote the light-assisted production of fuels and commodity chemicals is very appealing for energy crisis and climate change amelioration. Herein, we have prepared a series of Co-doped hydroxyapatite (HAP) catalysts with different Co content. The materials structure has been widely investigated by XRD, FT-IR, HRTEM, XPS, XAS, as well as computational simulations based on Density Functional Theory (DFT) with PBE functional. At low Co loading, there is a partial substitution of Ca cations in the HAP structure, while higher loadings promote the precipitation of small (∼ 2 nm) Co nanoparticles on the HAP surface. For the optimal Co content, a constant CO rate of 62 mmol·g−1·h−1 at 1 sun illumination and 400 °C, with the material being stable for 90 h. Visible and NIR photons have been determined responsible of the light-assisted activity enhanced. Mechanistic studies based on both experimental and DFT simulations show that H2 preferentially adsorbs to metallic Co, while CO2 adsorbs to the HAP surface oxygen. Moreover, both direct photo- and plasmon-driven contributions have been separated in order to study their mechanisms independently. [Display omitted] •A series of Co-doped hydroxyapatite (CoHAP) at various Co loadings (3.46–11.38%) have been prepared.•Characterization indicates that Co2+ replaces Ca2+ in the HAP lattice up to 5.88%.•At higher loading Co2+ migrates outside the HAP lattice and forms small Co3O4 nanoparticles.•Under continuous flow at 400 °C, the optimal CoHAP produces 62 mmol CO·g−1·h−1.•The material is stable for at least 90 h without activity decay