Attraction in Action: Reduction of Water to Dihydrogen Using Surface-Functionalized TiO2 Nanoparticles

Abstract

The reactivity of a heterogeneous rhodium(III) and ruthenium(II) complex-functionalized TiO2 nanoparticle (NP) system is reported. The ruthenium and rhodium metal complexes work in tandem on the TiO2 NPs surface to generate H2 through water reduction under simulated and normal sunlight irradiation. The functionalized TiO2 NPs outperformed previously reported homogeneous systems in turnover number (TON) and frequency (TOF). The influence of individual components within the system, such as pH, additive, and catalyst, were tested. The NP material was characterized using TGA-MS, 1H NMR spectroscopy, FTIR spectroscopy, solid absorption spectroscopy, and ICP-MS. Gas chromatography was used to determine the reaction kinetics and recyclability of the NP-supported photocatalyst.

Nanoparticulate Perovskites for Photocatalytic Water Reduction

“…The water reduction reaction conditions were consistent with the conditions in the previous work with TiO 2 NPs [ 20 ]. Triethanolamine (TEOA) was added as a sacrificial electron donor, K 2 [PtCl 4 ] as a catalyst to facilitate H 2 formation (feasibly by the formation of Pt nanoparticles), bpy as an additive, aqueous H 2 SO 4 for altering the solution pH.…”

“…Pristine SrTiO 3 and BaTiO 3 NPs were purchased from Sigma-Aldrich Chemie GmbH (Buchs, Switzerland) and had diameter sizes of <100 and 50 nm, respectively; further characterizations are reported in the Supplementary Materials . The anchoring ligand 1 was prepared as previously described [ 20 ]. Instrumentation details are given in the Supplementary Materials .…”

“…Pristine SrTiO 3 or BaTiO 3 NPs were activated as previously reported [ 20 ]. The NPs (2.00 g) were dispersed by sonication for 15 min in dilute aqueous HNO 3 (30 mL, 3.0 M).…”

“…The functionalization was performed as previously reported [ 20 ]. Anchoring ligand 1 (10.0 mg, 31.6 µmol, 1.0 eq.)…”

“…In previous studies, we have shown that the binding of photo- and redox-active Rh and Ru coordination compounds onto TiO 2 NP surfaces can be used successfully for H 2 production, with the catalytic activity of the NP-supported catalyst outperforming previously reported, related homogeneous catalysts [ 20 ]. Another promising class of photocatalysts are perovskite-type oxides MTiO 3 (M = Ca, Sr or Ba).…”