Insights into the Performance of CoxNi1-xTiO3 Solid Solutions as Photocatalysts for Sun-Driven Water Oxidation

Driving a NiTiO3 photocatalyst for the oxygen evolution reaction with near-infrared light

A nickel titanate (NTO) photocatalyst has been developed for the oxygen evolution reaction (OER) with an exceptionally broad light wavelength excitation ranging from visible to infrared. Specifically, by loading CoOx as the co-catalyst, the apparent quantum yields for the OER were ca. 2.2%, 1.0%, and 0.8% at wavelengths of 470, 760, and 850 nm, respectively. The achievements reveal that the NTO photocatalyst is highly efficient even under illumination with near-infrared (NIR) light, which confers the potential for highly efficient solar-driven oxidation reactions.

Design of noble metal-free CoTiO3/Zn0.5Cd0.5S heterostructure photocatalyst for selective synthesis offurfuraldehyde combined withH2production

The development of photocatalytic systems composed of earth-abundant metal-based catalysts for efficient production of clean fuel, H₂ as well as value-added chemicals is of significant importance towards sustainable generation of energy resources. Consequently, herein we report rational construction of Z-scheme CoTiO₃/xZn_0.5Cd_0.5S (x = 5 (S1), 10 (S2), 15 (S3) and 20 wt% (S4)) heterostructures featuring suitable band structure for efficient photocatalytic reduction of protons of water to H₂ combined with selective oxidation of furfuryl alcohol (biomass derivative) to a value-added product, furfuraldehyde. Electron microscopy analysis of heterostructure S2 revealed that Zn_0.5Cd_0.5S nanoparticles are decorated over the surface of CoTiO₃ microrods. The photocatalytic studies showed higher catalytic performance by S2, for selective oxidation of furfuryl alcohol to furfuraldehyde with 95% yield coupled with a H₂ generation rate of 1929 μmol g^-1h^-1 which is about 4-fold higher than that of pristine Zn_0.5Cd_0.5S. The enhanced catalytic performance of heterostructure S2 has been ascribed to synergistic interaction aided by the Z-scheme heterojunction formation between CoTiO₃ and Zn_0.5Cd_0.5S. Overall, this work demonstrates the application of noble metal-free photocatalyst for simultaneous production of H₂ and value-added chemical under mild and environment-friendly conditions.

Metal Titanate (ATiO3, A: Ni, Co, Mg, Zn) Nanorods for Toluene Photooxidation under LED Illumination

The increasing air pollution taking place in virtue of human activity has a novel impact in our health. Heterogeneous photocatalysis is a promising way of degrading volatile organic compounds (VOCs) that makes the quest of new and improved photocatalysts of great importance. Herein, perovskite-related materials ATiO3 with A = Mg, Ni, Co, Zn were synthesized through an ethylene glycol-mediated root, with ethylene glycol being used as a solvent and ligand. Characterization techniques such as X-ray diffraction (XRD), scanning electron microscopy, and energy dispersive X-ray spectroscopy (SEM/EDX), transmission electron microscopy (TEM), UV-vis spectroscopy, Raman spectroscopy, Fourier transform infrared (FT-IR), and photoluminescence spectroscopy (PL) were used in order to confirm the structure, the nanorod morphology, their absorption in UV-vis, and the separation efficiency of photogenerated charge carriers. The highest photoactivity was observed for ZnTiO3 in which 62% of toluene was decomposed after 60 min under LED illumination (54 mW/cm2).

A type-II interband alignment heterojunction architecture of cobalt titanate integrated UiO-66-NH2: A visible light mediated photocatalytic approach directed towards Norfloxacin degradation and green energy (Hydrogen) evolution

Environmental pollution and energy scarcity is a major issue of the current scenario which forbear the progress of developing world. To overcome these problems towards a sustainable future, the utilization of sunlight by means of photocatalysis can be regarded as a best and suitable pathway. To validate this purpose, design and development of efficient heterogeneous photocatalyst for harvesting solar energy should be the major research concern for scientific community. In this regard herein, we have prepared a series of stable and efficient CoTiO₃/UiO-66-NH₂ p-n junction mediated heterogeneous photocatalyst by hydrothermal method. The functionalised linker of UiO-66-NH₂ provided an intimate interfacial contact with CoTiO₃ by Co/TiON ionic interaction, as proved by HRTEM and XPS analysis. Moreover the inverted V-shaped Mott-Schottky plot confirmed the junction formation in the optimised CoTiO₃/UiO-66-NH₂ material. In addition, EIS and PL analysis also provides sufficient evidence about the hindrance of active species recombination in composite as a result of p-n hetero junction. LC-MS characterization technique traces the assorted intermediate species produced in the course of photodegradation of Norfloxacin and confirms its complete degradation to corresponding CO₂, H₂O and NH₄⁺ by the optimised CoTiO₃/UiO-66-NH₂. The highest photo-catalytic activity obtained towards Norfloxacin degradation is 90.13% and H₂ production is 530.87 µmol in 1 h. The enhanced photo-catalytic reaction follows Type-II p-n hetero junction charge transfer mechanism and thus, paves a new way to design MOF based heterojunction photocatalyst for diverse photo catalytic performance.

Copper-Substituted NiTiO3 Ilmenite-Type Materials for Oxygen Evolution Reaction

Single Ni_1-xCu_xTiO₃ (0.05 ≤ x ≤ 0.2) Ilmenite-type phases were successfully prepared through a solid-state reaction route using divalent metal nitrates as precursors and characterized. Their electrocatalytic performance for oxygen evolution reaction (OER) in alkaline media is presented. The Cu content was determined (0.05 ≤ x ≤ 0.2) by X-ray diffraction. A thorough powder neutron diffraction study was carried out to identify the subtle changes caused by copper substitution in the structure of NiTiO₃. The evolution of the optical and magnetic properties with the Cu content was also investigated on the raw micrometer-sized particles. A reduction in particle size down to ≈15 nm was achieved by ball-milling the raw powder prepared by the solid-state reaction. The best catalytic activity for OER was obtained for nanometer-sized particles of Ni_0.8Cu_0.2TiO₃ drop-casted on the Cu plate. For this electrode, a current density of 10 mA cm^-2 for oxygen production was generated at 345 and 470 mV applied overpotentials with 1 and 0.1 M NaOH solutions as electrolytes, respectively. The catalyst retained this OER activity at 10 mA cm^-2 for long-term electrolysis with a faradic efficiency of 90% for O₂ production in a 0.1 M NaOH electrolyte.