ABSTRACT
Electrochemical carbon dioxide reduction is a mild and eco-friendly approach for CO2 mitigation and producing value-added products. For selective electrochemical CO2 reduction, single-crystalline Au particles (octahedron, truncated-octahedron, and sphere) are synthesized by consecutive growth and chemical etching using a polydiallyldimethylammonium chloride (polyDDA) surfactant, and are surface-functionalized. Monodisperse, single-crystalline Au nanoparticles provide an ideal platform for evaluating the Au surface as a CO2 reduction catalyst. The polyDDA-Au cathode affords high catalytic activity for CO production, with >90% Faradaic efficiency over a wide potential range between -0.4 and -1.0 V versus RHE, along with high durability owing to the consecutive interaction between dimethylammonium and chloride on the Au surface. The influence of polyDDA on the Au particles, and the origins of the enhanced selectivity and stability are fully investigated using theoretical studies. Chemically adsorbed polyDDA is consecutively affected the initial adsorption of CO2 and the stability of the *CO2 , *COOH, and *CO intermediates during continuous CO2 reduction reaction. The polyDDA functionalization is extended to improving the CO Faradaic efficiency of other metal catalysts such as Ag and Zn, indicating its broad applicability for CO2 reduction.
ABSTRACT
The design of active, stable, and cost-effective electrocatalysts for the H2 evolution reaction (HER) in alkaline conditions is important for electrochemical systems such as the chloro-alkaline process and H2 production. Here we report catalysts comprising Pt on Ni single crystalline spines (Pt/Ni-SP) with high activity and stability for HER in alkaline solution with proposed mechanism. The Pt/Ni-SP catalysts are prepared by dispersing platinum nanoparticles (1.7-3.1 nm) on the single-crystalline spines (Ni-SP) of Ni urchin-like particles. The size and coverage of Pt nanoparticles on Ni-SP are increased with increases in the Pt loading amount. X-ray diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy are performed to observe the structure of the Pt/Ni-SP catalyst. The catalysts achieve the mass activity of 1.11 A mg-1(Pt), comparing favorably to Pt/C catalysts with the mass activity of 0.33 A mg-1(Pt) at 0.05 V overpotential. The Tafel slope of the Pt/Ni-SP catalyst is approximately 30 mV dec-1, similar to that of Pt, while Pt/Ni-SP is very stable in alkaline solution, like Ni. The synergistic effect of Pt/Ni-SP is ascribed to H spillover from Pt to Ni.
ABSTRACT
This study evaluated the prevalence of posttraumatic stress disorder (PTSD) and the severity of PTSD symptoms in survivors, rescuers and witnesses of terrorist attacks on Khyber bazaar, Qissa Khawani bazaar, and All Saints Church in Peshawar city area. Cross-sectional survey is carried out on a sample of one hundred survivors, rescuers and witness of terrorist attacks using structured interviews to assess the severity of posttraumatic stress, five months after the attacks. The study period extended from January 24, 2014 to March 24, 2014 which constitutes a total of period of 8 weeks. PTSD symptoms are measured using Posttraumatic Symptom Scale Interview (PSSI) and conferred to a diagnosis of PTSD at 5 months. Additionally, the severity of PTSD symptoms were determined using PSSI scores, severity ranged from 0-51. Of the one hundred survey respondents, 88% were males and 12% were females. Forty percent (40%) had attained 10 years of education, matriculation, but irrespective of the gender or educational status, all had some degree of PTSD. Sixty-six (66%) percent respondents are diagnosed as having moderate PTSD while 11% of the sample suffered from severe PTSD level. Age, gender, occupation and education level did not have any correlation with PTSD development. The contemporary findings indicate that any person who has witnessed or survived catastrophes of terrorist activities like bomb blast or being exposed to suicide attacks is at risk for developing PTSD, and there is necessity to deliver specialized post-disaster mental health facilities to the people having substantial levels of PTSD after calamities of such great intensity.
