Degradation mechanism of hydrogen-terminated porous silicon in the presence and in the absence of light

Abstract

Si is well-known semiconductor that has a fundamental bandgap energy of 1.12 eV. Its photogenerated electrons in the conduction band can react with the ubiquitous oxygen molecules to yield ⋅O2− radicals, but the photogenerated holes in the valance band can’t interact with OH− to produce ⋅OH radicals. In this paper, we study the degradation of methyl orange (MO) by hydrogen-terminated porous Si (H-PSi) in the presence and in the absence of light. The absorption spectra of the degraded MO solutions indicated that the H-PSi had superior degradation ability. In the dark, the reduction of dye occurs simply by hydrogen transfer. Under room light, however, some of the dye molecules can be reduced by hydrogen transfer first and then decomposed in the conduction and valance bands. This result should be ascribed to its wide band gap energies centered at 1.79-1.94 eV.

Enhancing Photocatalytic Attributes of Perovskite Nanocrystals in Aqueous Media via Ligand Engineering

“…When CsPbBr 3 /NKE-12 NCs are photoexcited in an aqueous solution, these free radicals can be generated via two pathways: (i) photogenerated electrons reducing dissolved O 2 to superoxide (O 2 ·– ) radicals and (ii) photogenerated holes reacting with OH – to form hydroxyl (OH · ) radicals. Although the free OH – in the aqueous solution has positive potential compared to the valence band edge holes of CsPbBr 3 /NKE-12, the surface-bound OH – species may possess a more negative redox potential and could react with the holes to undergo OH · radical formation. , To investigate the operative reaction pathway, we used BHT, as the O 2 ·– scavenger , and TEOA, as the hole scavenger. , While the polymerization decreased to some extent in the presence of TEOA, the reaction was almost entirely quenched in the presence of BHT. The kinetics of the control reactions was monitored by FTIR spectroscopy and is presented as the polymerization degree with time in Figure a (see Figure S5 for more details).…”

“…In the presence of TEMPO, a well-known radical quencher, 58,59 no polymerization was observed, suggesting a radical-based reaction pathway. Figure S4a shows no decrease in the characteristic vibrational peak intensity (=C−H bending frequency region) 48,60 To investigate the operative reaction pathway, we used BHT, as the O 2…”