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Salinity gradient power reverse electrodialysis: Cation exchange membrane design based on polypyrrole-chitosan composites for enhanced monovalent selectivity

Highlights • PyCS composite used for surface modification of CEMs by chemical polymerization. • Membrane properties vary with Py concentration exhibiting optimal range (0–0.1 M). • 3-Fold increase in monovalent selectivity of modified membranes over pristine ones. • Increased OCV and P d for RED tested with modified membranes in multi-ion solution. • Conducting polymers as prospective materials to design selective membranes for RED. Abstract Reverse electrodialysis (RED) is one of the most promising membrane-based processes for renewable energy generation from mixing two solutions of different salinity. However, the presence of Mg 2+ in natural water has been shown to drastically reduce open circuit voltage (OCV) and output power of RED. To alleviate this challenge, commercial cation exchange membranes (CEM) supplied by Fujifilm Manufacturing Europe B.V. (The Netherlands) were chemically modified by polypyrrole (PPy)/chitosan (CS) composites under controlled Pyrrole (Py) concentration (0.025–1 M) and polymerization time (0–8 h). The modified membranes were physically characterized by FTIR, SEM and EDX along with the determination of key electrochemical properties like ion exchange capacity, ionic conductivity, monovalent selectivity and swelling degree. The monovalent selectivity (Na + vs Mg 2+ ) of the modified membranes, evaluated based on flux of ions by diffusion dialysis, indicated up to 3-fold improvement compared to pristine membranes inline with the enhanced OCV (up to 20%) during RED test in multi-ion solution. This was obtained without significant change in membrane and interface resistances as depicted by electrochemical impedance spectroscopy. The modified membranes displayed power densities in the range of 0.6–1.5 W/m 2 MP (MP: membrane pair) with more than 42% improvement compared to pristine membranes during RED test with multi-ion solutions. Although there is a gap for further improvement, these findings highlight a promising use of conducting polymers to design a highly selective and conductive membrane for RED. Graphical abstract Download high-res image (232KB) Download full-size image

Chemical Engineering Journal EI,SCI,SCIE | 2020 | 380

FeS2 nanoparticles embedded in N/S co-doped porous carbon fibers as anode for sodium-ion batteries

Highlights • FeS 2 @CF-NS were synthesized by electrostatic spinning with subsequent calcination. • The carbon backbone buffers the volume expansion. • The doped N, S and defect sites facilitate fast and stable Na + /e − exchange. • The FeS 2 nanoparticles and FeS 2 nanoflakes shorten the Na + diffusion distance. • Capacitive Na + storage mechanism contributes to the rate performance. Abstract FeS 2 is a promising electrode material for sodium ion batteries (SIBs) because of its high theoretical capacity, rich reserves, and eco-friendly nature. In this study, N and S doped (N, S-co-doped) carbon fibers (CFs) encapsulated FeS 2 nanoparticles (5–12 nm) and adherent FeS 2 nanoflakes (denoted as FeS 2 @CF-NS), were synthesized by electrostatic spinning and subsequent thermal treatment. In this structure, the FeS 2 nanoparticles and the FeS 2 nanoflakes shorten the Na + diffusion distance; the N, S co-doping and defect-rich sites in the carbon fibers accelerate the Na + /e − transmission and buffer the volume expansion during the Na-FeS 2 conversion reaction. These merits synergistically contribute to the notable sodium storage performance of FeS 2 @CF-NS. As anode for Na-ion half batteries, the FeS 2 @CF-NS exhibits high capacity (637.1 mAh/g at 1 A/g after 400 cycles) and excellent rate capacity (431.1 mAh/g at 5 A/g). Kinetic analysis confirms that this composite structure stimulates the pseudocapacitance Na + storage mechanism and enables a capacitive contribution ratio as high as 92.7% with respect to the total capacity. In combination with Na 3 V 2 (PO 4 ) 3 -C cathode, the FeS 2 @CF-NS also achieves remarkably high specific capacity (561.1 mAh/g at 1 A/g after 500 cycles) and stable cyclability (338.6 mAh/g at 5 A/g after 5000 cycles) in full cells. Graphical abstract Download high-res image (197KB) Download full-size image

Chemical Engineering Journal EI,SCI,SCIE | 2020 | 380

Three birds with one stone: A ferric pyrophosphate based nanoagent for synergetic NIR-triggered photo/chemodynamic therapy with glutathione depletion

Highlights • A self-reinforcing nanoagent (FeP-ZnPc) with triple-function was designed. • The nanoagent could release Fe 3+ which consuming glutathione, generating Fe 2+ . • Reactive oxygen species yield in photodynamic therapy could boost Fenton reaction. • The therapeutic effect was enhanced via synergetic photo/chemodynamic therapy. Abstract Strategies utilizing reactive oxygen species (ROS) to cause cell death are widely practiced for cancer therapy, including photodynamic therapy (PDT) and chemodynamic therapy (CDT). However, the efficiency of PDT alone is greatly hindered by tumor hypoxia, laser penetration depth and the relatively low oxidation performance of 1 O 2 and its subsequent products H 2 O 2 . Meanwhile, CDT is limited by the deficiency of endogenous H 2 O 2 in cancer cells. If the ROS, produced in PDT process, served as the substrate in CDT, the total ROS production would be greatly enhanced. However, the increased ROS could be scavenged by the overexpressed glutathione (GSH) in cancer cells, impairing the effect of PDT and CDT. Thus, in this study, a self-reinforcing ferric pyrophosphate based nanoagent (FeP-ZnPc) for synergetic NIR-triggered photo/chemodynamic therapy with glutathione depletion ability was constructed. The constructed FeP-ZnPc exhibited “triple use”: PDT, CDT and GSH depletion function. Upon internalized into cancer cells, the FeP-ZnPc could release Fe 3+ which underwent a redox reaction with GSH, resulting in GSH depletion and the production of Fe 2+ . Upon laser, Zinc phthalocyanine (ZnPc) in the FeP-ZnPc could generate ROS for PDT directly. Moreover, the elevated ROS particularly H 2 O 2 could serve as the substrate of CDT, accelerating the Fenton reaction process, producing the strongest oxidants, hydroxyl radical ( OH) and leading to ROS burst to expedite cell death. This combination strategy of enhancing ROS production and inhibiting ROS elimination could eventually break down the redox homeostasis and enhance the ROS-mediated cancer therapy. Graphical abstract FeP-ZnPc combining the effect of enhancing ROS production and inhibiting ROS elimination effectively broken down the intracellular redox homeostasis. Download high-res image (152KB) Download full-size image

Chemical Engineering Journal EI,SCI,SCIE | 2020 | 380

Electricity generation and microbial community of single-chamber microbial fuel cells in response to Cu2O nanoparticles/reduced graphene oxide as cathode catalyst

Highlights • The electricity generation of MFC with Cu 2 O-rGO/CC was higher compared with Pt-C/CC. • Cu 2 O/rGO possessed excellent catalytic activity and promoted O 2 diffusion to cathode. • Cu 2 O/rGO as cathode catalyst increased the relative abundance of Geobacter in anode. • The antibacterial property of Cu 2 O/rGO inhibited the growth of microbial in cathode. Abstract Metal oxides supported on carbonaceous substrates hold a wide application prospect in replace of Pt-based cathode catalyst for improving performance of microbial fuel cells (MFCs) due to their low cost, abundant storage and excellent oxygen reduction reaction (ORR) catalytic activity. However, there is little information available on Cu 2 O nanoparticles/reduced graphene oxide (Cu 2 O/rGO) as cathode catalyst of MFCs and its effect on the electricity generation and microbial community. In this work, the output voltage, coulombic efficiency and microbial community in a single-chamber MFC with Cu 2 O/rGO cathode catalyst were investigated comparing with commercial Pt/C. The results indicated that the MFC with Cu 2 O/rGO cathode catalyst produced higher output voltage (0.223 V) and coulombic efficiency (92.5%) comparing with commercial Pt/C (0.206 V, 90.3%). Besides, Cu 2 O/rGO cathode catalyst possessed excellent ORR catalytic activity and promoted O 2 diffusion to cathode surface. Interestingly, the most relative abundance of known electrogenic microorganisms Geobacter in anode biofilm of MFC with Cu 2 O/rGO cathode catalyst (49.28%) was higher than that with commercial Pt/C (32.33%). The microbial abundance and diversity in cathode biofilm of MFC with Cu 2 O/rGO catalyst were obviously lower than those with commercial Pt/C due to the antibacterial property of Cu 2 O/rGO, which could expose more catalytic active sites on cathode and further improve electricity generation performance of MFCs. These results have provided insights into the potential application of Cu 2 O/rGO as a high catalytic active and antibacterial cathode catalyst to replace commercial Pt/C for electricity generation. Graphical abstract The Cu 2 O nanoparticles decorated reduced graphene oxide (Cu 2 O/rGO) as cathode catalyst of simple-chamber microbial fuel cells can produce higher the maximum output voltage and coulombic efficiency compared with commercial Pt/C (20 wt%) catalyst. Download high-res image (120KB) Download full-size image

Chemical Engineering Journal EI,SCI,SCIE | 2020 | 380

Effect of reduced graphene oxide load into TiO2 P25 on the generation of reactive oxygen species in a solar photocatalytic reactor. Application to antipyrine degradation

Highlights • Effects of rGO on TiO 2 band gap and absorption were studied. • The ROS generation by solar TiO 2 and TiO 2 /rGO was discussed. • Antipyrine solar degradation-ROS generation relation was evaluated. • TiO 2 holes were also found to be responsible primary species. Abstract TiO 2 -based photocatalysis is intensively investigated for efficient degradation of emerging environmental contaminants, but the generation of reactive oxygen species during such photocatalytic reactions is often underresearched. In this paper, we study the formation of reactive oxygen species under real solar irradiation on TiO 2 P25 loaded with reduced graphene oxide (rGO). TiO 2 /rGO composites were prepared by mixing graphene oxide and TiO 2 P25, followed by hydrothermal treatment. The band gap of TiO 2 was not affected in the composites but the optical properties of the systems changed due to the morphology and presence of rGO. When these composites were studied under solar irradiation, the generation rate of hydroxyl HO radicals under solar light was higher in pure TiO 2 than in TiO 2 /rGO, but also their decay with time, so TiO 2 /rGO eventually presented higher HO concentration at longer times. Moreover, adding rGO to TiO 2 also affected the concentration of superoxide O 2 − and singlet oxygen 1 O 2 radicals, which we assign to the charge transfer between TiO 2 and rGO and the presence of remaining holes on the surface. The amount of generated hydrogen peroxide H 2 O 2 and consumed in these systems was practically the same, so its concentration remained low. The catalytic systems developed were tested in the solar photocatalytic degradation of antipyrine, demonstrating the relationship between the evolution of generated reactive oxygen species along the reaction time and the consumption of antipyrine. The TiO 2 valence band holes were also found to be the responsible primary species along the course of reaction especially in the final mineralization step. Graphical abstract Download high-res image (87KB) Download full-size image

Chemical Engineering Journal EI,SCI,SCIE | 2020 | 380