Sn:In₂O₃ and Sn:In₂O₃/NiS₂ Core–Shell Nanowires on Ni, Mo Foils and C Fibers for H₂ and O₂ Generation

Abstract

Sn:In2O3 nanowires have been grown by the vapor liquid solid mechanism on Si, Ni, Mo, and C fibers. These were used to obtain Sn:In2O3/NiS2 core–shell nanowires by the deposition of 10 nm Ni over the Sn:In2O3 nanowires followed by post growth processing under H2S between 100 and 200 °C. The Sn:In2O3/NiS2 nanowires have diameters of ≈100 nm and lengths up to ≈100 μm and consist of cubic bixbyite Sn:In2O3 surrounded by 3 nm NiS2 crystalline quantum dots with a cubic crystal structure. Higher temperatures of 300–500 °C result in the formation of NiS2 quantum dots and cubic In3S4 branches around the Sn:In2O3. We find that the p-type NiS2 in contact with n-type Sn:In2O3 NWs gives rectifying current–voltage (IV) characteristics due to the formation of a p–n heterojunction with a straddling type band alignment where electrons are confined to the n-type Sn:In2O3 core and holes in the p-type NiS2, as shown by self-consistent Poisson–Schrödinger calculations in the effective mass approximation. The gas evolution of O2 and H2 was measured using the Sn:In2O3/NiS2 nanowires as the anode and Pt as the cathode in a two-compartment photoelectrochemical cell containing 1 M KOH (aq) and 0.5 M H2SO4 (aq), respectively, under light of 1 sun. We obtain 7.8 μL/min of O2 and 15.0 μL/min of H2 at an overpotential of 0.2 V and 25 °C from the Sn:In2O3/NiS2 nanowires on C. These are ≈35% larger than those obtained from plain Sn:In2O3 nanowires attributed to the existence of the p–n junction.

Synthesis of Z-scheme Mn-CdS/MoS2/TiO2 ternary photocatalysts for high-efficiency sunlight-driven photocatalysis

“…Since the discovery 1 of photoelectrochemical splitting of water on titanium dioxide (TiO 2 ) electrodes, semiconductor-based photoelectrolysis of water to hydrogen and oxygen has attracted more and more public attention. 2 –7 Solar photocatalysis technology, as an eco-friendly and economic technology, can split water to produce H 2 and degrade organic pollutants, thereby remediating environment and producing green chemical energy (e.g. H 2 gas) at the same time.…”