4 research outputs found
Role of Surface Oxygen Vacancies and Lanthanide Contraction Phenomenon of Ln(OH)<sub>3</sub> (Ln = La, Pr, and Nd) in Sulfide-Mediated Photoelectrochemical Water Splitting
Herein,
we report the role of surface oxygen vacancies and lanthanide
contraction phenomenon on HS<sup>ā</sup> anion adsorption and
desorption in the sulfide-mediated photoelectrochemical water splitting
of LnĀ(OH)<sub>3</sub> (Ln = La, Pr, and Nd). The LnĀ(OH)<sub>3</sub> were synthesized via a solvothermal route using ethylenediamine
as the solvent. The surface defects are characterized by Raman, X-ray
photoelectron spectroscopy (XPS), electron paramagnetic resonance
(EPR), and high-resolution transmission electron microscopy analyses.
The photoelectrochemical water-splitting behavior of LnĀ(OH)<sub>3</sub> enriched with surface oxygen vacancies has been examined in a 1
M Na<sub>2</sub>S solution under illumination conditions. LaĀ(OH)<sub>3</sub> exhibited a highly stable and saturated current density of
ā¼26 mA/cm<sup>2</sup> at 0.8 V (vs Ag/AgCl). Similarly, the
hydroxides of Pr and Nd demonstrated current densities of 18 and 14
mA/cm<sup>2</sup>, respectively, at 0.8 V (vs Ag/AgCl). A reduction
trend in the saturated current densities from La to Nd indicates the
lanthanide contraction phenomenon, where the basicity decreases in
the same order. The results also demonstrate that the surface adsorption
of the HS<sup>ā</sup> anion in the active sites of the surface
oxygen vacancies played a vital role in enhancing the photoelectrochemical
water-splitting behavior of LnĀ(OH)<sub>3</sub>. The stability of LnĀ(OH)<sub>3</sub> was examined after 4 h of chronoamperometry studies at 0.8
V (vs Ag/AgCl) and analyzed using X-ray diffraction, Fourier transform
infrared, Raman, and EPR and XPS analyses. The results show that the
LnĀ(OH)<sub>3</sub> exhibited excellent stability by demonstrating
their phase purity after photoelectrochemical water splitting. We
propose LnĀ(OH)<sub>3</sub> as highly stable photoelectrochemical water-splitting
catalysts in highly concentrated sulfide-based electrolytes and anticipate
LnĀ(OH)<sub>3</sub> systems to be explored in a major scale for the
production of H<sub>2</sub> as an ecofriendly process
Heterostructured Au NPs/CdS/LaBTC MOFs Photoanode for Efficient Photoelectrochemical Water Splitting: Stability Enhancement via CdSe QDs to 2D-CdS Nanosheets Transformation
The
electrochemical stability of MOFs in aqueous medium is most
essential for MOFs based electrocatalysts for hydrogen production
via water splitting. Since most MOFs suffer from instability issues
in aqueous systems, there is enormous demand for electrochemically
stable MOFs catalysts. Herein, we have developed a simple postsynthesis
surface modification protocol for La (1,3,5-BTC) (H<sub>2</sub>O)<sub>6</sub> metalāorganic frameworks (LaBTC MOFs) using Mercaptopropionic
acid (MPA), to attain electrochemical stability in aqueous mediums.
The MPA treated LaBTC MOFs exhibited better stability than the bare
LaBTC. Further, to facilitate light harvesting properties of LaBTC
MOFs, Au nanoparticles (NPs) and CdSe quantum dots (QDs) are functionalized
on LaBTC. The sensitization of LaBTC with Au NPs and CdSe QDs enhances
the light harvesting properties of LaBTC in the visible region of
solar spectrum. Using as a photoanode, the electrode generates the
current density of ā¼80 mA/cm<sup>2</sup> at 0.8 V (vs Ag/AgCl)
during photoelectrochemical water splitting. The heterostructured
LaBTC photoanode demonstrates the long-term stability for the period
of 10 h. The electrode post-mortem analysis confirms the conversion
of CdSe QDs into single crystalline 2D-CdS nanosheets. The present
investigation reveals that CdS nanosheets together with SPR Au NPs
improve the photoelectrochemical water splitting activity and stability
of LaBTC MOFs