Modified, Solvothermally Derived Cr-doped SnO₂ Nanostructures for Enhanced Photocatalytic and Electrochemical Water-Splitting Applications

Abstract

Cr-doped SnO 2 nanostructures with a dopant concentration ranging from 1 to 5% have been successfully prepared using low-temperature modified solvothermal synthesis. The as-prepared nanoparticles showed a rutile tetragonal structure with a rough undefined morphology having no other elemental impurities. The particle shape and size, band gap, and specific surface area of the samples were investigated by scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, UV–visible diffused reflectance spectroscopy, and Brunauer–Emmett–Teller surface area studies. The optical band gap was found in the range of 3.23–3.67 eV and the specific surface area was in the range of 108–225 m 2 /g, which contributes to the significantly enhanced photocatalytic and electrochemical performance. Photocatalytic H 2 generation of as-prepared Cr-doped SnO 2 nanostructures showed improved effect of the increasing dopant concentration with narrowing of the band gap. Electrochemical water-splitting studies also stressed upon the superiority of Cr-doped SnO 2 nanostructures over pristine SnO 2 toward hydrogen evolution reaction and oxygen evolution reaction responses.

Hydrothermally Derived Hierarchical CuO Nanoflowers as an Efficient Photocatalyst and Electrocatalyst for Hydrogen Evolution

“…The attained onset potential of as‐synthesized CuO nanoflowers was found to be in proximity to the onset potential of iridium oxide electrocatalyst which is known to be the standard of electrocatalytic water splitting for oxygen evolution. The mechanism and reaction kinetics for electrocatalytic HER and OER responses were investigated by employing Tafel equation [7,36] . Figure 10 (c) and (d) shows the Tafel plots of as‐prepared CuO nanoflowers for HER and OER reactions, respectively.…”

“…For working electrode preparation, the ITO (Indium tin oxide) substrates with dimensions 1 × 1 cm 2 were pre‐treated to clean by ultrasonication with acetone, ethanol, and isopropanol respectively. A catalyst ink was prepared by mixing 3 mg of as synthesized nanocatalyst with 5 μL Nafion as binder and 1 ml of DMF (dimethylformamide) by sonication and then drop casted on ITO surface and dried at 60 °C in vacuum oven to attain the working electrode of as‐prepared CuO nanoflowers [7,29] …”

“…The photocatalytic reaction was performed in a 75 ml quartz cell with cylindrical neck offered for the air‐tight rubber septum to prevent the escape of gaseous reaction products. The specialized reaction cell containing 50 ml of double distilled water was loaded with 10 mg of as‐synthesized nanoparticles and added equimolar sodium sulphite/sodium sulphide (Na 2 SO 3 /Na 2 S) as sacrificial agent into it under constant stirring and de‐aerated with N 2 bubbling for 30 minutes [7,12,28] . Finally, the solution illuminated under a UV‐Vis lamp as light source (200 W, Hg−Xe arc lamp, Newport) and kept on magnetic stirrer for continuous stirring during the reaction.…”

“…There are various methods for the production of hydrogen such as fossil fuels, especially steam reforming of methane, oil/naphtha reforming, coal gasification, biomass, biological sources and water electrolysis [6] . The production of H 2 can be done by electrocatalytic, photocatalytic or photo‐electrocatalytic water splitting process is taken into consideration which is eco‐friendly and produces high purity H 2 [7–10] . The electrocatalytic process is one the promising technique for H 2 production, it involves the two coupled electrochemical half‐reaction, the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER).…”

“…[6] The production of H 2 can be done by electrocatalytic, photocatalytic or photoelectrocatalytic water splitting process is taken into consideration which is eco-friendly and produces high purity H 2 . [7][8][9][10] The electrocatalytic process is one the promising technique for H 2 production, it involves the two coupled electrochemical half-reaction, the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The development of HER and OER catalysts focuses on their individual development so that each of the half-cell reaction can be optimized.…”