RESUMO
Herein, a detailed investigation of the surface modification of a zinc oxide (ZnO) nanorod electrode with FeOOH nanoparticles dispersed in glycine was conducted to improve the water oxidation reaction assisted by sunlight. The results were systematically analysed in terms of the general parameters (light absorption, charge separation, and surface for catalysis) that govern the photocurrent density response of metal oxide as photoanode in a photoelectrochemical (PEC) cell. ZnO electrodes surface were modified with different concentration of FeOOH nanoparticles using the spin-coating deposition method, and it was found that 6-layer deposition of glycine-FeOOH nanoparticles is the optimum condition. The glycine plays an important role decreasing the agglomeration of FeOOH nanoparticles over the ZnO electrode surface and increasing the overall performance. Comparing bare ZnO electrodes with the ones modified with glycine-FeOOH nanoparticles an enhanced photocurrent density can be observed from 0.27 to 0.57â mA/cm2 at 1.23 VRHE under sunlight irradiation. The impedance spectroscopy data aid us to conclude that the higher photocurrent density is an effect associated with more efficient surface for chemical reaction instead of electronic improvement. Nevertheless, the charge separation efficiency remains low for this system. The present discovery shows that the combination of glycine-FeOOH nanoparticle is suitable and environmentally-friend cocatalyst to enhance the ZnO nanorod electrode activity for the oxygen evolution reaction assisted by sunlight irradiation.
RESUMO
Mono-nuclear fac-[Re(CO)3(ph2phen)(4,4'-bpy)]+ and di-nuclear [(ph2phen)(CO)3Re(4,4'-bpy)Re(ph2phen)(CO)3]2+ complexes, ph2phen = 4,7-diphenyl-1,10-phenanthroline and 4,4'-bpy = 4,4'-bipyridine, were synthesized and characterized by 1H NMR, UV-visible and FT-IR spectroscopy. Also, their photophysical properties were investigated using steady-state and time-resolved emission spectroscopy. Both complexes showed UV absorption assigned to intraligand, 1ILph2phen, and metal-to-ligand charge transfer, 1MLCTReâph2phen, transitions, and typical 3MLCTReâph2phen emission (Ï = 0.360 and τ = 3.81 µs; Ï = 0.177 and τ = 1.90 µs for mono- and di-nuclear, respectively). Additionally, the luminescence of these complexes is quenched by hydroquinone with approximately 4 × 109 L mol-1 s-1 rate constant for the bimolecular excited state, kq. The Stern-Volmer constants, KSV, determined by the emission intensity and lifetime showed excellent correlation, which is indicative of the dynamic quenching. The similarity of the bimolecular rate constants between the two complexes implies that the photoinduced electron transfer is the main pathway with a very small (or no) influence of the proton transfer step. The results provide additional insight into the role of the protonable nitrogen atom in the photophysical properties of rhenium(i) complexes, using a dyad architecture.
