Enhanced adsorption capacity and selectivity towards strontium ions in aqueous systems by sulfonation of CO2 derived porous carbon

Oxygen-enriched carbon materials derived from carbon dioxide were functionalized using sulfonic acid to remove Sr2+ ions from aqueous solutions. Synthesized sulfonated porous carbon materials (PC-SO3H) showed higher adsorption capacity and selectivity towards Sr2+ than non-functionalized porous carbons (PC). The formation of the C-SO3H functional group in PC-SO3H and its ability to proton exchange with Sr2+ was the main contributor to the enhanced performance. The maximum uptake capacity of Sr2+ by PC-SO3H was 18.97 mg g−1, which was 1.74 times greater than PC. PC-SO3H removed 99.9% and 97.6% of Sr2+ from aqueous solutions with initial Sr2+ concentrations of 5 mg L−1 and 10 mg L−1, respectively. Sr2+ adsorption showed rapid kinetics, reaching the adsorption equilibrium within 1 h with high adsorption capacity at equilibrium which is 3.52 times greater than that of PC. Additionally, PC-SO3H selectively adsorbed Sr2+ even in the presence of excess amounts of competing ions. Sulfonation of oxygen-enriched carbon had a significant effect on enhancing the affinity towards Sr2+ and suppressing adsorption towards other competing ions

Self-motivated, thermally oxidized hematite nanoflake photoanodes: Effects of pre-polishing and ZrO2 passivation layer

High-temperature thermal oxidation of an Fe foil produces a high-quality, crystalline hematite nanoflake suitable as a photoanode for the photoelectrochemical (PEC) water oxidation. Physical pre-polishing of the foil surface has a profound effect in the formation of a vertically-aligned nanoflakes of hematite phase with extended (110) planes by removing the loosely-bonded oxide layer. When the surface of the photoanode is modified with a ZrO2 passivation layer and a cobalt phosphate co-catalyst, the charge recombination at the photoanode-electrolyte interface is greatly suppressed to improve its overall PEC activity. As a result, the photocurrent density at 1.10 VRHE under 1 sun condition is enhanced from 0.22 mA cm(-2) for an unmodified photoanode to 0.59 mA cm(-2) for the fully modified photoanode, and the photocurrent onset potential is shifted cathodically by 400 mV. Moreover, the photoanode demonstrates outstanding stability by showing steady production of H-2 and O-2 gases in the stoichiometric ratio of 2:1 in a continuous PEC operation for 10 h. (C) 2021 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved

Microwave-assisted metal-ion attachment for ex-situ zirconium doping into hematite for enhanced photoelectrochemical water splitting

Ex-situ doping into hematite films is carried out via a short-duration (-60 s) microwave-assisted metalions attachment (MWMA) of tetravalent Zr4 thorn ion on the surface of FeOOH/FTO, followed by high temperature annealing (HTA) to fabricate Zr4 thorn :Fe2O3/FTO photoanode for photoelectrochemical (PEC) water splitting. Compared to a simple dipping attachment without microwave irradiation, this MWMA allows a much larger amount of attached Zr4 thorn -ions on the FeOOH precursor, leading to a properly doped photoanode of much higher PEC activity. The primary effect of Zr4 thorn doping is to improve the charge transport characteristics in the bulk of hematite. In addition, it also boosts charge injection efficiency at the semiconductor and electrolyte interface by forming an inadvertent passivation layer and promoting hole transfer via surface states. As a result, the Zr4 thorn :Fe2O3/FTO photoanode shows a higher photocurrent density of 1.54 mA cm-2 at 1.23 VRHE under 1 Sun irradiation relative to undoped Fe2O3/FTO (1.02 mA cm-2) or Zr4 thorn :Fe2O3/FTO (1.19 mA cm-2) prepared without MWMA. (c) 2022 Elsevier Ltd. All rights reserved

Boosting Photocatalytic Performance of Inactive Rutile TiO₂ Nanorods under Solar Light Irradiation: Synergistic Effect of Acid Treatment and Metal Oxide Co-catalysts

In the present work, we accomplish the boosting of photocatalytic performance by the synergistic effect of acid treatment and transition metal oxide co-catalysts on molten salt rutile TiO₂ nanorods. FT-IR and XPS (oxygen deconvolution) results confirmed that the amount of hydroxyl groups increased on the surface of rutile TiO₂ nanorods (TO-NRs) after acid treatment. HR-TEM analysis revealed fine dispersion of metal oxide on the surface of acid treated TiO₂ nanorods (ATO-NRs). The photocatalytic activities of as-prepared (TO-NRs), acid treated (ATO-NRs), metal oxide loaded (MTO-NRs), and both acid treated and metal oxide loaded (MATO-NRs) nanorods were compared based on the rate kinetics and dye degradation efficiencies. Cobalt oxide (1 wt %) loaded and 1.0 M acid treated TiO₂ nanorods (Co/ATO-NR) exhibited the higher photocatalytic degradation efficiency for Orange-II dye degradation and inactivation of <i>S. typhimurium</i> pathogen compared to other photocatalysts under solar irradiation. Photoelectrochemical analysis demonstrated that the charge transfer process in Co/ATO-NR is significantly higher than that in the untreated samples. The improved photocatalytic activity of inactive TO-NRs might be due to enhanced charge transfer of finely dispersed metal oxides on the OH-rich surface of acid treated TiO₂ nanorods