Participation of electrochemically inserted protons in the hydrogen evolution reaction on tungsten oxides.

Understanding the mechanisms by which electrodes undergo the hydrogen evolution reaction (HER) is necessary to design better materials for aqueous energy storage and conversion. Here, we investigate the HER mechanism on tungsten oxide electrodes, which are stable in acidic electrolytes and can undergo proton-insertion coupled electron transfer concomitant with the HER. Electrochemical characterization showed that anhydrous and hydrated tungsten oxides undergo changes in HER activity coincident with changes in proton composition, with activity in the order HxWO3·H2O > HxWO3 > HxWO3·2H2O. We used operando X-ray diffraction and density functional theory to understand the structural and electronic changes in the materials at high states of proton insertion, when the oxides are most active towards the HER. H0.69WO3·H2O and H0.65WO3 have similar proton composition, structural symmetry, and electronic properties at the onset of the HER, yet exhibit different activity. We hypothesize that the electrochemically inserted protons can diffuse in hydrogen bronzes and participate in the HER. This would render the oxide volume, and not just the surface, as a proton and electron reservoir at high overpotentials. HER activity is highest in HxWO3·H2O, which optimizes both the degree of proton insertion and solid-state proton transport kinetics. Our results highlight the interplay between the HER and proton insertion-coupled electron transfer on transition metal oxides, many of which are non-blocking electrodes towards protons.

Electrochemical proton insertion modulates the hydrogen evolution reaction on tungsten oxides.

The development of new electrocatalysts for the hydrogen evolution reaction (HER) could reduce the dependence on Pt and other rare metals and enable large-scale production of hydrogen with near-zero carbon emissions. Mechanistic insight into the electrocatalytic activity of a material helps to accelerate the development of new electrocatalysts. Alternative electrocatalyst materials such as transition metal oxides and sulfides can undergo insertion reactions that change their properties. Recent reports indicate that the presence of inserted ions can influence the electrocatalytic activity. Here, we utilized a materials chemistry approach to understand the role of proton insertion in the HER activity of the layered tungsten oxide hydrates (WO3·xH2O, x = 1, 2). We synthesized a series of tungsten oxide hydrates along with an octylamine-pillared tungsten oxide (OA-WO3). We used cyclic voltammetry to study the electrochemical reactivity of each material and performed ex situ x-ray diffraction and Raman spectroscopy to understand bulk and surface structural changes during electrochemical cycling. We show an inverse relationship between the degree of proton insertion and HER overpotential in tungsten oxides: the lack of proton insertion leads to a high overpotential for the HER. We discuss three hypotheses for how proton insertion leads to the HER activity in WO3·xH2O: (1) proton insertion changes the electronic band structure of WO3·xH2O, (2) the presence of bulk protons can influence ΔGH,ads at the surface sites, and (3) the inserted protons may participate in the HER mechanism on WO3·xH2O. Overall, this work shows the critical role of proton insertion in enabling the high HER activity in tungsten oxides.

Using risk-based analysis and geographic information systems to assess flooding problems in an urban watershed in Rhode Island.

This article provides an overview of the use of risk-based analysis (RBA) in flood damage assessment, and it illustrates the use of Geographic Information Systems (GIS) in identifying flood-prone areas, which can aid in flood-mitigation planning assistance. We use RBA to calculate expected annual flood damages in an urban watershed in the state of Rhode Island, USA. The method accounts for the uncertainty in the three primary relationships used in computing flood damage: (1) the probability that a given flood will produce a given amount of floodwater, (2) the probability that a given amount of floodwater will reach a certain stage or height, and (3) the probability that a certain stage of floodwater will produce a given amount of damage. A greater than 50% increase in expected annual flood damage is estimated for the future if previous development patterns continue and flood-mitigation measures are not taken. GIS is then used to create a map that shows where and how often floods might occur in the future, which can help (1) identify priority areas for flood-mitigation planning assistance and (2) disseminate information to public officials and other decision-makers.

Characteristics and predictors of full and partial recovery from generalized anxiety disorder in primary care patients.

The current study examined the naturalistic course of generalized anxiety disorder (GAD) in a sample of 113 primary care patients across a 2-year period. Initial diagnoses were established using structured clinical interviews according to DSM-IV diagnostic criteria. Results indicated that the majority of patients meeting DSM-IV diagnostic criteria for GAD were still symptomatic to some degree after 2 years of follow-up. Rates of full and partial recovery from GAD, however, were found to be higher than those reported for previous studies of GAD in psychiatric patients. Diagnostic comorbidity, severity of psychosocial impairment, and gender were found to be significantly associated with achieving full or partial recovery from GAD. Psychiatric treatment was not found to be associated with time to full or partial recovery from GAD symptoms, likely due to a treatment-biasing effect. These results underscore that GAD is a chronic and persistent illness in primary care patients.

Chronicity in posttraumatic stress disorder and predictors of the course of posttraumatic stress disorder among primary care patients.

The present study examined the course of posttraumatic stress disorder (PTSD) in a sample of 84 primary care patients. More specifically, this study investigated the role of Axis I comorbidity, psychosocial impairment, and treatment participation in the maintenance of an episode of chronic PTSD and whether patients at follow-up met criteria for PTSD (full remission) or continued to exhibit residual PTSD symptoms and impairment (partial PTSD). Diagnostic structured interviews established all clinical diagnoses and information on the course of anxiety disorder symptoms, psychosocial functioning, and treatment status. Using a prospective, longitudinal design, this study found that during the first 2 years of follow-up, the probability of no longer meeting full DSM-IV criteria for PTSD was .69, and .18 for full remission from PTSD. The number of comorbid anxiety disorders and degree of psychosocial impairment at intake were significantly related to remission status (i.e., full and partial PTSD). This study suggests that, in a primary care setting, PTSD is a persistent illness, and that many subjects who have recovered from PTSD continue to suffer from subthreshold symptoms of PTSD.

Factor structure and stability of the Anxiety Sensitivity Index in a longitudinal study of anxiety disorder patients.

The past decade witnessed considerable debate over the factor structure of the Anxiety Sensitivity Index (ASI), with an eventual consensus emerging that supported a hierarchically organized factor structure. The present study attempted to replicate and examine the overall stability and utility of the hierarchical ASI factor pattern using a large sample of outpatients participating in an ongoing longitudinal study of anxiety disorders. Results supported a hierarchical factor structure for the ASI consisting of three lower-order factors measuring physical concerns, mental incapacitation concerns, and social concerns, all of which loaded significantly on a single second-order factor. Correlational analyses show good test-retest reliability and consistent patterns of intercorrelation for these factor-derived subscales across a 10-month time frame. Additional analyses provide support for the discriminant validity of the ASI subscales with regard to individuals with specific anxiety disorders. The theoretical implications of these findings for future evaluations of anxiety sensitivity are discussed.