TY - JOUR

T1 - Influence of the preparation conditions on the morphology and photocatalytic performance Pt-modified hexaniobate composites

AU - Nunes, Barbara Nascimento

AU - Patrocinio, Antonio Otavio T.

AU - Bahnemann, Detlef

N1 - This work was supported by Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG, PPM-00220-17), Con- selho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES). The authors are also thankful to the Grupo de Materiais Inorgânicos do Triângulo (GMIT), a research group supported by FAPEMIG (APQ-00330-14). AOTP is thankful to Alexander Von Humboldt Foundation for the fellowship in Germany. DWB acknowledges financial sup- port from Saint Petersburg State University (Research Grant 39054581).

PY - 2019/7/9

Y1 - 2019/7/9

N2 - The preparation of lamellar nanostructures through exfoliation of stacked niobates is an interesting approach to the development of photocatalysts for energy conversion and environmental remediation. These materials exhibit a rich surface chemistry and several nanocomposites can be produced through intercalation or impregnation of suitable precursors. In this work, the influence of the physico-chemical preparation conditions on the photocatalytic activity of Pt-hexaniobate nanocomposites was investigated aiming at the establishment of the main factors that control their photoreactivities. Modification of hexaniobate layers were carried out by adsorption and impregnation methods, using [Pt(NH 3) 4]Cl 2 (Pt1) and H 2PtCl 6 (Pt2), respectively. The addition of platinum precursors (1% wt.) were performed in the presence of the exfoliating agent tert-butylammonium hydroxide, sNb, or after acidic precipitation followed by resuspension in plain water, eNb. All samples were submitted to photoirradiation to reduce the platinum precursors and the effect of a previous thermal treatment was also evaluated. It was observed that H 2 evolution from aqueous methanol solutions is more favored on hexaniobate nanosheets (eNb-Pt1 and eNb-Pt2) instead of scrolled layers (sNb-Pt1 and sNb-Pt2), independent on the platinum precursor. Moreover, residual tert-butylammonium can act as hole scavenger and decrease the degradation rates for methanol oxidation in sNb samples. The curled layers observed for sNb samples seem to favor the photodegradation of cationic species, such as methylene blue. Thermal treatment at 500 °C leads to morphological changes with a decrease of the specific surface area due to restacking of the individual layers along with some curling. As a result, the H 2 evolution rates strongly decreases in relation to the non-sintered samples, suggesting that the 'soft' photoreduction of platinum precursors is the best method for preparation of these photocatalysts. The correlations between the preparation conditions and the photocatalytic activity for different photoreactions can allow the development of optimized materials for specific applications.

AB - The preparation of lamellar nanostructures through exfoliation of stacked niobates is an interesting approach to the development of photocatalysts for energy conversion and environmental remediation. These materials exhibit a rich surface chemistry and several nanocomposites can be produced through intercalation or impregnation of suitable precursors. In this work, the influence of the physico-chemical preparation conditions on the photocatalytic activity of Pt-hexaniobate nanocomposites was investigated aiming at the establishment of the main factors that control their photoreactivities. Modification of hexaniobate layers were carried out by adsorption and impregnation methods, using [Pt(NH 3) 4]Cl 2 (Pt1) and H 2PtCl 6 (Pt2), respectively. The addition of platinum precursors (1% wt.) were performed in the presence of the exfoliating agent tert-butylammonium hydroxide, sNb, or after acidic precipitation followed by resuspension in plain water, eNb. All samples were submitted to photoirradiation to reduce the platinum precursors and the effect of a previous thermal treatment was also evaluated. It was observed that H 2 evolution from aqueous methanol solutions is more favored on hexaniobate nanosheets (eNb-Pt1 and eNb-Pt2) instead of scrolled layers (sNb-Pt1 and sNb-Pt2), independent on the platinum precursor. Moreover, residual tert-butylammonium can act as hole scavenger and decrease the degradation rates for methanol oxidation in sNb samples. The curled layers observed for sNb samples seem to favor the photodegradation of cationic species, such as methylene blue. Thermal treatment at 500 °C leads to morphological changes with a decrease of the specific surface area due to restacking of the individual layers along with some curling. As a result, the H 2 evolution rates strongly decreases in relation to the non-sintered samples, suggesting that the 'soft' photoreduction of platinum precursors is the best method for preparation of these photocatalysts. The correlations between the preparation conditions and the photocatalytic activity for different photoreactions can allow the development of optimized materials for specific applications.

KW - 2D-based photocatalysts

KW - lamellar materials

KW - niobates

UR - http://www.scopus.com/inward/record.url?scp=85071066886&partnerID=8YFLogxK

U2 - 10.1088/1361-648x/ab2c5e

DO - 10.1088/1361-648x/ab2c5e

M3 - Article

VL - 31

JO - Journal of Physics Condensed Matter

JF - Journal of Physics Condensed Matter

SN - 0953-8984

IS - 39

M1 - 394001

ER -