Optoelectronic structure and photocatalytic applications of Na(Bi,La)S2 solid solutions with tunable bandgaps
Type
ArticleKAUST Department
Catalysis for Energy Conversion (CatEC)Chemical Science Program
KAUST Catalysis Center (KCC)
Physical Science and Engineering (PSE) Division
Date
2019-04-03Online Publication Date
2019-04-03Print Publication Date
2019-05-14Permanent link to this record
http://hdl.handle.net/10754/631881
Metadata
Show full item recordAbstract
NaLa1-xBixS2 solid solutions with tunable bandgaps were synthesized, and their optoelectronic structures and photocatalytic performance were investigated via experimental and theoretical approaches. The solid-solution powders with various La/Bi ratios were synthesized with Na2CO3, La2O3 and Bi2O3 as precursors and via sulfurization with flowing CS2 at 800 °C for 2 h. The Vegard’s law behavior of cell parame-ters showed a perfect Bi/La solid solution in the cubic NaLa1-xBixS2 with the associated linear variation of the lattice constants. On the con-trary, the combination of diffuse reflectance UV−Vis spectroscopy with density functional theory (DFT) calculations employing the HSE06 functional reveals a monotonic but non-linear variation of the bandgap of the solid solution. While consistent valence band maxi-mum (VBM) was obtained in NaLa1-xBixS2—consisting mainly of S 3p orbitals—the conduction band minimum (CBM) was contributed by discrete Bi orbitals present at more positive potential than La. As a result, the slight inclusion of Bi caused a drastic shift in the bandgap, and 24% Bi substitution provided an absorption edge closer to that of pure NaBiS2. Systematic DFT calculations on NaLa1-xBixS2 deter-mined the optoelectronic properties for improved photovoltaic and photocatalytic performance with a Bi-rich sample rather than a La-rich counterpart; i.e., there were larger absorption coefficients, smaller effective masses, and larger dielectric constants for Bi-rich samples versus La-rich samples. The NaLa1-xBixS2 particles decorated with Pt nanoparticles show maximum hydrogen evolution performance with x = 0.02-0.06 of Bi samples consistent with the compensating effects between photon absorption capacity and loss of electromotive force with decreasing bandgap.Citation
BaQais A, Tymińska N, Le Bahers T, Takanabe K (2019) Optoelectronic structure and photocatalytic applications of Na(Bi,La)S2 solid solutions with tunable bandgaps. Chemistry of Materials. Available: http://dx.doi.org/10.1021/acs.chemmater.9b00031.Sponsors
Research reported in this work was supported by the King Abdullah University of Science and Technology (KAUST). AB acknowledges Princess Nourah bint Abdulrahman University (PNU) for financial support. NT and TLB acknowledge the PSMN computation center for providing calculation resources.Publisher
American Chemical Society (ACS)Journal
Chemistry of MaterialsAdditional Links
https://pubs.acs.org/doi/10.1021/acs.chemmater.9b00031ae974a485f413a2113503eed53cd6c53
10.1021/acs.chemmater.9b00031