Fe3O4/granular activated carbon as an efficient three-dimensional electrode to enhance the microbial electrosynthesis of acetate from CO2Zhu, Hao; Dong, Zhiwei; Huang, Qiong; Song, Tian-shun; Xie, Jingjing
doi: 10.1039/c9ra06255fpmid: 35529973
Microbial electrosynthesis (MES) allows the transformation of CO2 into value-added products by coupling with renewable energy. The enhancement in the microbial activity and electron transfer rate via a new electrode modification method is essential for developing MES. Here, three groups of granular activated carbon decorated by Fe3O4 (Fe3O4/GAC) with mass fractions of 23%, 38% and 50% were prepared and compared with bare GAC. The volumetric acetate production rate of MES with Fe3O4/GAC-38% was the highest (0.171 g L−1 d−1), which was 1.4 times higher that of the control (bare GAC), and the final acetate concentration reached 5.14 g L−1 within 30 days. Linear sweep voltammetry and microbial community analyses suggested that Fe3O4/GAC facilitates extracellular electron transfer and improves the enrichment of electrochemically active bacteria. Fe3O4/GAC is an effective three-dimensional electrode material that enhances biofilm activity on GAC and improves MES efficiency.
Tinospora cordifolia derived biomass functionalized ZnO particles for effective removal of lead(ii), iron(iii), phosphate and arsenic(iii) from waterVyas, Gaurav; Bhatt, Shreya; Paul, Parimal
doi: 10.1039/c9ra07042gpmid: 35530005
Owing to the vast diversity in functional groups and cost effectiveness, biomass can be used for various applications. In the present study, biomass from Tinospora cordifolia (TnC) was prepared and grafted onto the surface of ZnO particles following a simple method. The TnC functionalized ZnO particles (ZnO@TnC) were characterized and exhibited excellent adsorption properties towards Pb2+ (506 mg g−1), Fe3+ (358 mg g−1) and PO43− (1606 mg g−1) and the Fe3+ adsorbed ZnO@TnC adsorbs AsO21− (189 mg g−1); the metal ions and anions were analyzed by ICP and IC. For reuse of ZnO@TnC, a desorption study was successfully carried out using NaOH and EDTA for PO43− and Pb2+, respectively; Fe3+ was further used for adsorption of As(iii). The adsorption fits well with the Langmuir adsorption isotherm model and the adsorption kinetic data are best fitted with a pseudo-second-order equation. The system developed may be useful for treatment of waste water and industrial effluents.
Highly efficient and giant negative electrocaloric effect of a Nb and Sn co-doped lead zirconate titanate antiferroelectric film near room temperatureZhao, Quanliang; Sheng, Tianyu; Pang, Lei; He, Guangping; Di, Jiejian; Zhao, Lei; Hou, Zhiling; Cao, Maosheng
doi: 10.1039/c9ra06551bpmid: 35529984
Adiabatic temperature variation (ΔT), coefficient of performance (COP) and electrocaloric coefficient (ΔT/ΔE) play important roles in evaluating the comprehensive performance of solid-state cooling technology based on the electrocaloric effect (ECE). A Nb and Sn co-doped lead zirconate titanate antiferroelectric film, Pb0.99Nb0.02(Zr0.85Sn0.13Ti0.02)O3 (PNZST), shows a highly efficient and giant negative ECE. The ΔT, |ΔT/ΔE| and COP are about −9.8 K, 0.0488 K cm kV−1 and 35.53 at around 50 °C, respectively. The full width at half maximum of the ΔT peak is about 37 °C. Phenomenological analysis indicates that the highly efficient and giant negative ECE is associated with the first-order transition that has a discontinuous polarization change with increasing temperature.
Near-field infrared microscopy of nanometer-sized nickel clusters inside single-walled carbon nanotubesNémeth, Gergely; Datz, Dániel; Pekker, Áron; Saito, Takeshi; Domanov, Oleg; Shiozawa, Hidetsugu; Lenk, Sándor; Pécz, Béla; Koppa, Pál; Kamarás, Katalin
doi: 10.1039/c9ra07089cpmid: 35529972
Nickel nanoclusters grown inside single-walled carbon nanotubes (SWCNT) were studied by infrared scattering-type scanning near-field optical microscopy (s-SNOM). The metal clusters give high local contrast enhancement in near-field phase maps caused by the excitation of free charge carriers. The experimental results are supported by calculations using the finite dipole model, approximating the clusters with elliptical nanoparticles. Compared to magnetic force microscopy, s-SNOM appears much more sensitive to detect metal clusters inside carbon nanotubes. We estimate that these clusters contain fewer than ≈700 Ni atoms.
The versatile Co2+/Co3+ oxidation states in cobalt alumina spinel: how to design strong blue nanometric pigments for color electrophoretic displaySerment, B.; Brochon, C.; Hadziioannou, G.; Buffière, S.; Demourgues, A.; Gaudon, M.
doi: 10.1039/c9ra06395apmid: 35529990
Blue cobalt inorganic pigments with spinel-type structure have been revisited in order to understand the origin of blackening at low temperatures and to design strong blue nanosized materials. Starting from a sol–gel process, the so-called Pechini route, the correlation between the structural features (inversion rate, Co over-stoichiometry, Co valence states) of the spinel network and its thermal history under air up to high temperatures (T = 1400 °C) allows concluding that the stabilization of CoIII in octahedral sites is at the origin of the blackening of the pigment annealed at low and medium temperatures. EELS coupled with TEM analyses (occurrence of multiple phases with various Al/Co atomic ratios) lead to us to conclude definitively about the variation of Co valence states. A top-down (mechanical grinding) and a bottom-up approach lead to the definition of a synthesis route (co-precipitation in basic medium followed by annealing at medium temperatures under Ar) allowing the design of strong blue pure nano-sized pigments to be incorporated in inks. Hybrid blue positively charged particles were mixed with white negatively charged particles to formulate dual-colour inks. A dual-colour display was filled with the as-prepared inks and tested under ±150 V.
An advanced and efficient Co3O4/C nanocomposite for the oxygen evolution reaction in alkaline mediaMugheri, Abdul Qayoom; Tahira, Aneela; Aftab, Umair; Abro, Muhammad Ishaq; Mallah, Arfana Begum; Memon, Gulam Zuhra; Khan, Humaira; Abbasi, Mazhar Ali; Halepoto, Imran Ali; Chaudhry, Saleem Raza; Ibupoto, Zafar Hussain
doi: 10.1039/c9ra07224apmid: 35529970
The design of efficient nonprecious catalysts for the hydrogen evolution reaction (HER) or the oxygen evolution reaction (OER) is a necessary, but very challenging task to uplift the water-based economy. In this study, we developed a facile approach to produce porous carbon from the dehydration of sucrose and use it for the preparation of nanocomposites with cobalt oxide (Co3O4). The nanocomposites were studied by the powder X-ray diffraction and scanning electron microscopy techniques, and they exhibited the cubic phase of cobalt oxide and porous structure of carbon. The nanocomposites showed significant OER activity in alkaline media, and the current densities of 10 and 20 mA cm−2 could be obtained at 1.49 and 1.51 V versus reversible hydrogen electrode (RHE), respectively. The impedance study confirms favorable OER activity on the surface of the prepared nanocomposites. The nanocomposite is cost-effective and can be capitalized in various energy storage technologies.
Gold nanostructures for the sensing of pH using a smartphoneBiswas, Subrata; Chakraborty, Jayjeet; Agarwal, Avinash; Kumbhakar, Pathik
doi: 10.1039/c9ra07101fpmid: 35529967
Recently, metal nanostructures have been found to be capable of recognizing small changes in their surrounding environment, which can be utilized as significant sensing tools. In this study, we demonstrated colorimetric sensing of pH by gold nanostructures (GNs) using a simple smartphone. An indigenously developed Android app based on the CIELab 1931 analysis, which could run in a smartphone, was used for the precise determination of the pH value of liquid media. The pH value of an unknown solution obtained from the developed Android app was also compared with that obtained from the conventional ratiometric technique and a commercial pH meter. In another endeavor, it was found that the synthesized GNs demonstrated a high energy transfer efficiency from a donor (namely, the rhodamine 6G, (Rh 6G)) dye. This property of the GNs can be utilized further in the future for studying different bimolecular activities within the human body. It was found that the photoluminescence (PL) of Rh 6G was quenched when it was kept in the vicinity of the synthesized GNs, which was explained in terms of the Förster energy transfer mechanism. Thus, the present study will open up a plethora of opportunities for researchers to employ the nanostructures of gold and other metals in developing low-cost and Internet of Things (IoT)-based sensing devices using only a smart phone.
Alternative electrodes for HTMs and noble-metal-free perovskite solar cells: 2D MXenes electrodesCao, Junmei; Meng, Fanning; Gao, Liguo; Yang, Shuzhang; Yan, Yeling; Wang, Ning; Liu, Anmin; Li, Yanqiang; Ma, Tingli
doi: 10.1039/c9ra06091jpmid: 35529991
The high cost of hole transporting materials (HTMs) and noble metal electrodes limits the application of perovskite solar cells (PSCs). Carbon materials have been commonly utilized for HTMs and noble-metal-free PSCs. In this paper, a more conductive 2D MXene material (Ti3C2), showing a similar energy level to carbon materials, has been used as a back electrode in HTMs and noble-metal-free PSCs for the first time. Seamless interfacial contact between the perovskite layer and Ti3C2 material was obtained using a simple hot-pressing method. After the adjustment of key parameters, the PSCs based on the Ti3C2 electrode show more stability and higher power conversion efficiencies (PCE) (13.83%, 27% higher than that (10.87%) of the PSCs based on carbon electrodes) due to the higher conductivity and seamless interfacial contact of the MXene electrode. Our work proposes a promising future application for MXene and also a good electrode candidate for HTM and the noble-metal-free PSCs.
First principles calculations of the thermodynamic stability of Ba, Zr, and O vacancies in BaZrO3Raja, N.; Murali, D.; Satyanarayana, S. V. M.; Posselt, M.
doi: 10.1039/c9ra07978epmid: 35530013
The temperature dependence of the stability of bulk BaZrO3 (BZO) and of the vacancies in this material are investigated by considering phonon contributions to the free energy. The stability diagram of BZO is determined for different chemical environments. With increasing temperature the stability region becomes smaller which is particularly caused by the strong temperature dependence of the chemical potential of gaseous oxygen. The free formation energy of Ba, Zr, and O vacancies in BZO is calculated for all possible charge states and for different atomic reservoirs. While the free formation energy of Zr vacancies is strongly influenced by temperature a weaker dependence is found for Ba and O vacancies. This also has an effect on the charge transition levels at different temperatures. The present results demonstrate that O poor reservoir conditions and a Fermi level close to the valence band maximum favour a high concentration of doubly positively charged O vacancies which is a prerequisite to get a large number of protonic defects and good proton conductivity. In such a chemical environment the number of Ba and Zr vacancies is low so that Ba and Zr deficiencies are not an important issue and BZO remains sufficiently stable.