“One-Pot” Synthesis and Photocatalytic Hydrogen Generation with Nanocrystalline Ag(0)/CaTiO₃ and in Situ Mechanistic Studies

Abstract

We describe a previously not reported “one-pot” synthesis of nanocrystalline Ag(0)/CaTiO3 in aqueous suspension and the following in situ photocatalytic testing in the same suspension to generate hydrogen. The Ag(0)/CaTiO3 showed an enhancement of photocatalytic hydrogen generation rate vs CaTiO3 precursor. The obtained Ag(0)/CaTiO3 photocatalyst was ex situ characterized by XPS, XRD, UV–vis diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) spectroscopy, and concluded to have metallic silver nanoparticles on the surface of calcium titanate nanocrystals. The three photocatalytic mechanisms in Ag(0)/CaTiO3 were considered: (a) bandgap narrowing in CaTiO3, (b) enhanced electron–hole separation in CaTiO3, and (c) excitation of surface plasmon resonance (SPR) in metallic Ag nanoparticles. In mechanistic studies, photocatalytic suspensions with CaTiO3 precursor, with silver precursor, and with both CaTiO3 and Ag precursors to form Ag(0)/CaTiO3 were illuminated, flash-frozen to 77 K, and characterized by in situ “conventional” PL spectroscopy and in situ synchronous luminescence spectroscopy. On the basis of the complementary ex situ and in situ studies, an enhanced electron–hole separation in Ag(0)/CaTiO3 is suggested.

Enhanced Photocatalytic Performance and Mechanism of Au@CaTiO3 Composites with Au Nanoparticles Assembled on CaTiO3 Nanocuboids

“…Compared to Ag NPs, Au NPs offer an advantage of higher chemical stability. However, there is no work concerned with the Au NPs modified CaTiO 3 photocatalysts, though Ag NPs have been frequently used as a co-catalyst to improve the photocatalytic performance of CaTiO 3 [56,57,58]. Here we also systematically investigated the growth process of CaTiO 3 photocatalysts.…”

Hydrogen evolution via noble metals based photocatalysts: A review

“…It has been discovered that the rate of H2 production in the vicinity of RhCrOx/Pr-LaFeO3 and triethanolamine (TEOA) as sacrificial agents is the highest compared to methanol and ethanol. The "one-pot" synthesis of Ag/calcium titanate nanocrystals in aqueous dilution has been proposed by Alzahrani et al [109]. Upon deposition of metallic Ag nanoparticles on CaTiO3, hydrogen generation rate has been increased, because of the stimulation of surface plasmon resonance (SPR) in silver, increased e -/h + separation in CaTiO3 and narrowing of the bandgap in CaTiO3.…”

“…Ru atoms/multi-edged TiO2 spheres Solvothermal method and calcination of as-synthesized ME-PT, 20 ml of methanol, Xe lamp, 300 W 7.2 mmolg -1 h -1 [105] Rh-doped Ca2Nb3O10 sheet Thermal annealing, 10 vol % CH3OH, xenon lamp 500 W 77 mmolg -1 h -1 [106] Ag/CaTiO3 "One-pot" synthesis, medium pressure Hg lamp 450 W, 20 min, 10 vol% solution of glycerol 167 μmolg -1 h -1 [109] Ag−TiO2/SiO2 Hydrothermal approach, 2 mL of methanol and 10 mL of water, Xe Arc lamp 150 W, Ar gas 738 μmolg -1 h -1 [110] Ag@Ni/TiO2 One-step photoinduced deposition, four 365-nm LEDs (23.0 mW cm −2 ), 20 min, D-520 Nafion and ethanol (1:1)…”

Interplay between Mesocrystals of CaTiO3 and Edge Sulfur Atom Enriched MoS2 on Reduced Graphene Oxide Nanosheets: Enhanced Photocatalytic Performance under Sunlight Irradiation

“…Particularly, the alkaline‐earth metal perovskite oxides are of great scientific interest for inventive applications owing to their remarkable merits like high chemical and photostability, low cost, earth‐abundant constituents, non‐toxic nature, favorable conduction band (CB) (above −0.1 eV) and valence band (VB) (below +2.0 eV) potential, etc . As a prototype, calcium titanate (CaTiO 3 ) with orthorhombic crystal structure has attracted growing attention in the field of photocatalysis …”