Binary vanadium pentoxide carbon-graphene foam composites derived from dark red hibiscus sabdariffa for advanced asymmetric supercapacitor.

The development of advanced electrode materials derived from biomass for the next generation of energy storage devices, such as supercapacitors with high specific energy and specific power coupled with a good cycle stability, is required to meet the high demand for electric vehicles and portable devices. In this study, sustainable binary vanadium pentoxide carbon-graphene foam composites (V2O5@C-R2HS/GF) were synthesized using a solvothermal method. The X-ray diffraction, Raman and FTIR techniques were used to study the structural properties of the composites (V2O5@C-R2HS/20 mg GF and V2O5@C-R2HS/40 mg GF). The SEM micrographs displayed an accordion-like morphology resulting from the graphene foam-modified V2O5@C-R2HS composite. The V2O5@C-R2HS, V2O5@C-R2HS/20 mg GF and V2O5@C-R2HS/40 mg GF composites were evaluated in a three-electrode configuration using 6 M potassium hydroxide (KOH) as an aqueous electrolyte. Furthermore, a two-electrode device was carried out by fabricating an asymmetric device (V2O5@C-R2HS/GF//AC) where V2O5@C-R2HS/20 mg GF was used as a positive electrode and activated carbon (AC) as a negative electrode at a cell voltage of 1.6 V in 6 M KOH. The V2O5@C-R2HS/GF//AC showed a high specific energy and specific power values of 55 W h kg-1 and 707 W kg-1, respectively, at a specific current of 1 A g-1. The asymmetric device presented a good stability test showing 99% capacity retention up to 10 000 cycles and was confirmed by the floating time up to 150 h with specific energy increasing 23.6% after the first 10 h. This article is part of the theme issue 'Bio-derived and bioinspired sustainable advanced materials for emerging technologies (part 2)'.

Effect of porosity enhancing agents on the electrochemical performance of high-energy ultracapacitor electrodes derived from peanut shell waste.

In this study, the synthesis of porous activated carbon nanostructures from peanut (Arachis hypogea) shell waste (PSW) was described using different porosity enhancing agents (PEA) at various mass concentrations via a two-step process. The textural properties obtained were depicted with relatively high specific surface area values of 1457 m2 g-1, 1625 m2 g-1 and 2547 m2 g-1 for KHCO3, K2CO3 and KOH respectively at a mass concentration of 1 to 4 which were complemented by the presence of a blend of micropores, mesopores and macropores. The structural analyses confirmed the successful transformation of the carbon-containing waste into an amorphous and disordered carbonaceous material. The electrochemical performance of the material electrodes was tested in a 2.5 M KNO3 aqueous electrolyte depicted its ability to operate reversibly in both negative and positive potential ranges of 0.90 V. The activated carbon obtained from the carbonized CPSW:PEA with a mass ratio of 1:4 yielded the best electrode performance for all featured PEAs. The porous carbons obtained using KOH activation displayed a higher specific capacitance and the lower equivalent series resistance as compared to others. The remarkable performance further corroborated the findings linked to the textural and structural properties of the material. The assembled device operated in a neutral electrolyte (2.5 M KNO3) at a cell potential of 1.80 V, yielded a ca. 224.3 F g-1 specific capacitance at a specific current of 1 A g-1 with a corresponding specific energy of 25.2 Wh kg-1 and 0.9 kW kg-1 of specific power. This device energy was retained at 17.7 Wh kg-1 when the specific current was quadrupled signifying an excellent supercapacitive retention with a corresponding specific power of 3.6 kW kg-1. These results suggested that peanut shell waste derived activated carbons are promising candidates for high-performance supercapacitors.

A high energy density asymmetric supercapacitor utilizing a nickel phosphate/graphene foam composite as the cathode and carbonized iron cations adsorbed onto polyaniline as the anode.

This work presents the effect of different contents of graphene foam (GF) on the electrochemical capacitance of nickel phosphate Ni3(PO4)2 nano-rods as an electrode material for hybrid electrochemical energy storage device applications. Pristine Ni3(PO4)2 nano-rods and Ni3(PO4)2/GF composites with different GF mass loadings of 30, 60, 90 and 120 mg were synthesised via a hydrothermal method. The electrochemical behavior of pristine Ni3(PO4)2 and Ni3(PO4)2/GF composites were analysed in a three-electrode cell configuration using 6 M KOH electrolyte. The Ni3(PO4)2/90 mg GF composite sample exhibited the highest specific capacity of 48 mA h g-1 at a current density of 0.5 A g-1. The electrochemical behavior of the Ni3(PO4)2/90 mg GF composite was further analysed in a two-electrode hybrid asymmetric device. A hybrid asymmetric device was fabricated with Ni3(PO4)2/90 mg GF as the cathode and carbonized iron cations (Fe3+) adsorbed onto polyaniline (PANI) (C-FP) as the anode material (Ni3(PO4)2/90 mg GF//C-FP) and tested in a wide potential window range of 0.0-1.6 V using 6 M KOH. This hybrid device achieved maximum energy and power densities of 49 W h kg-1 and 499 W kg-1, respectively, at 0.5 A g-1 and had long-term cycling stability.

Correction: A high energy density asymmetric supercapacitor utilizing a nickel phosphate/graphene foam composite as the cathode and carbonized iron cations adsorbed onto polyaniline as the anode.

[This corrects the article DOI: 10.1039/C7RA12028A.].

[Water quality and personal hygiene in rural areas of Senegal]. / Qualité de l'eau et comportements hygiéniques des populations en milieu rural sénégalais.

INTRODUCTION: The high prevalence of diarrhea in developing countries is mostly due to poor water quality and hygiene practices. The purpose of this study was to assess water quality as well as hygiene practices and their determinants in Ngohé, i.e., a rural community (RC) in Senegal. METHOD: A combined approach consisting of a cross-sectional descriptive survey and bacterial analysis of water was used. Study was conducted in 312 randomly selected households. Data was collected through individual interviews with the assistance of a guide. Water for bacteriological analysis was collected from various sources, i.e., 3 modem borehole wells, 2 protected wells, and 10 traditional wells. Study points included home water treatment, drinking water source, latrine use, hand washing habits, and bacteria identified in water. A multiple regression model was used for data analysis. RESULTS: The household survey population was 59% male, 61% illiterate, and 93% married. Mean age was 44.8 +/- 18.1 years. Chlorination technique was inadequate in 62% of cases. Latrines were not restricted to adult use in 76% of homes. Hand washing was not performed at critical times in 94%. Drinking water was drawn from traditional wells in 48% of households, modem borehole wells in 45% and protected wells in 7%. Escherichia coli was found in water from all three sources and Vibrio cholerae was found in two traditional wells. Level of education, average monthly income, knowledge about chlorination techniques, and source of the water consumed were the main behavioral determinants (p < 0.05). CONCLUSION: Water treatment at the source and in the home as well as protection of water sources is necessary to ensure water quality. This will require effective public education campaigns and financial support for improvement of sanitary facilities.

[Evaluation of the cost of stroke management in Dakar, Senegal]. / Evaluation du coût de prise en charge des accidents vasculaires cérébraux à Dakar--Senegal.

The purpose of this one-year cross-sectional study conducted in 1997 was to estimate the direct cost of stroke management in the Neurology Department of Fann University Hospital in Dakar, Senegal. Data were collected about the type of care services required and related spending. Cost analysis was made in CFA Francs (CFAF), the Senegalese currency (1 USD = 500 CFAF in 1997). A total of 1260 patients were hospitalized in the department including 383 for stroke (30.4%). Mean age was 60.8 +/- 14.2 years and men accounted for 49.2% of the population. The mortality rate was 46.2% among hospitalized patients. A total of 33,573 medical acts were carried out including 12,052 (35.9%) for stroke management. The direct cost of stroke management was 32,614,442 CFAF with a mean cost of 78,426 CFAF per patient. The cost was 18,839 CFAF in the patient care unit (57.8%) and 4,954,635 CFAF in the neuroradiology unit (15.2%). The cost of health care personnel was 19,373,172 CFAF (59.4%) and the cost for drugs and other medical products was 8,253,246 CFAF. Health education programs aimed at increasing awareness of risk factors are needed to reduce the cost of stroke management in this difficult economic period.