Cascade electrocatalysis via AgCu single-atom alloy and Ag nanoparticles in CO2 electroreduction toward multicarbon products

Electrocatalytic CO2 reduction into value-added multicarbon products offers a means to close the anthropogenic carbon cycle using renewable electricity. However, the unsatisfactory catalytic selectivity for multicarbon products severely hinders the practical application of this technology. In this paper, we report a cascade AgCu single-atom and nanoparticle electrocatalyst, in which Ag nanoparticles produce CO and AgCu single-atom alloys promote C-C coupling kinetics. As a result, a Faradaic efficiency (FE) of 94 ± 4% toward multicarbon products is achieved with the as-prepared AgCu single-atom and nanoparticle catalyst under ~720 mA cm-2 working current density at -0.65 V in a flow cell with alkaline electrolyte. Density functional theory calculations further demonstrate that the high multicarbon product selectivity results from cooperation between AgCu single-atom alloys and Ag nanoparticles, wherein the Ag single-atom doping of Cu nanoparticles increases the adsorption energy of *CO on Cu sites due to the asymmetric bonding of the Cu atom to the adjacent Ag atom with a compressive strain.

Insights into Electrochemical CO2 Reduction on SnS2: Main Product Switch from Hydrogen to Formate by Pulsed Potential Electrolysis

Tin disulfide (SnS2) is a promising candidate for electrosynthesis of CO2-to-formate while the low activity and selectivity remain a great challenge. Herein, we report the potentiostatic and pulsed potential CO2RR performance of SnS2 nanosheets (NSs) with tunable S-vacancy and exposure of Sn-atoms or S-atoms prepared controllably by calcination of SnS2 at different temperatures under the H2/Ar atmosphere. The catalytic activity of S-vacancy SnS2 (Vs-SnS2) is improved 1.8 times, but it exhibits an exclusive hydrogen evolution with about 100% FE under all potentials investigated in the static conditions. The theoretical calculations reveal that the adsorption of *H on the Vs-SnS2 surface is energetically more favorable than the carbonaceous intermediates, resulting in active site coverage that hinders the carbon intermediates from being adsorbed. Fortunately, the main product can be switched from hydrogen to formate by applying pulsed potential electrolysis benefiting from in situ formed partially oxidized SnS2-x with the oxide phase selective to formate and the S-vacancy to hydrogen. This work highlights not only the Vs-SnS2 NSs lead to exclusively H2 formation, but also provides insights into the systematic design of highly selective CO2 reduction catalysts reconstructed by pulsed potential electrolysis.

Pt nanoparticles under oxidizing conditions - implications of particle size, adsorption sites and oxygen coverage on stability

Platinum nanoparticles are efficient catalysts for different reactions, such as oxidation of carbon and nitrogen monoxides. Adsorption and interaction of oxygen with the nanoparticle surface, taking place under reaction conditions, determine not only the catalytic efficiency but also the stability of the nanoparticles against oxidation. In this study, platinum nanoparticles in oxygen environment are investigated by systematic screening of initial nanoparticle-oxygen configurations and employing density functional theory and a thermodynamics-based approach. The structures formed at low oxygen coverages are described by adsorption of atomic oxygen on the nanoparticles whereas at high coverages oxide-like species are formed. The relative stability of adsorption configurations at different oxygen coverages, including the phase of fully oxidized nanoparticles, is investigated by constructing p-T phase diagrams for the studied systems.

Structures of Small Platinum Cluster Anions Ptn-: Experiment and Theory

The structures of platinum cluster anions Pt6--Pt13- have been investigated by trapped ion electron diffraction. Structures were assigned by comparing experimental and simulated scattering functions using candidate structures obtained by density functional theory computations, including spin-orbit coupling. We find a structural evolution from planar structures (Pt6-, Pt7-) and amorphous-like structures (Pt7--Pt9-) to structures based on distorted tetrahedra (Pt9--Pt11-). Finally, Pt12- and Pt13- are based on hcp fragments. While the structural parameters are well described by density functional theory computations for all clusters studied, the predicted lowest energy structure is found in the experiment only for Pt6-. For larger clusters, higher energy isomers are necessary to obtain a fit to the scattering data.

Assessment of rational drug use and prescribing in primary health care facilities in north west Ethiopia

A study on rational drug use was undertaken in nine health centres (HCs) and nine health stations (HSs) in Ethiopia. Prescribing, patient care and facility specific factors were measured using drug use indicators. Prescribing patterns of drugs were also assessed. With only few exceptions, the drug use indicators in HCs and HSs and between retrospective and prospective studies were similar despite differences in manpower and facilities. The average consultation time (in minutes) in HSs and HCs was 5.1 +/- 0.8 and 5.8 +/- 1.06, respectively. The dispensing time (in minutes) was 1.5 +/- 0.7 in HSs and 1.9 +/- 0.6 in HCs. Both patient care indicators seem to be adequate to influence patient satisfaction to the overall health service and patient knowledge of important dosage instructions. Most drugs (more than 89% in HCs and 71% in HSs) were actually dispensed from the health facilities and labelling was satisfactory. Prescribing by generic names (average: 75% in HCs and 83% in HSs) was encouraging. While the availability of key drugs was ensured, essential documents were missing in most facilities or they were unpopular for use, and those available required revision and updating. Polypharmacy in which the number of drugs/encounter was < 2.5 was minimal, but that a large proportion of the prescriptions contained two or more drugs could result in adverse drug-drug interactions. The most frequently prescribed drugs were anti-infectives and analgesics accounting for over 76% in HCs and 82% in HSs and in most cases they are probably prescribed with little justification. The exposure of patients to antibiotics (average: 60% in HCs and 65% in HSs) was unacceptably high to justify epidemiological trends. The high exposure of patients to injections, especially in the HSs (over 37%), should be seen from the health and economic points of view. The results revealed priority areas for intervention. They also provide standard references to compare drug use situations and their change over time in different settings, area and time in Ethiopia.

Child morbidity patterns in Ethiopia

This study is based on the 1983 Rural Health Survey of Ethiopia. Patterns and levels of child morbidity by age, sex, geographic region, and sanitary facilities are examined. Morbidity levels peak in the second year of life. Diarrhoeal diseases are of major importance, especially among infants and toddlers. Parasitic diseases, and respiratory diseases other than pneumonia, become increasingly important with age. There are no significant sex differentials in morbidity except for higher rates of diarrhoeal diseases among female children. Geographic differentials are quite marked with particularly high morbidity levels from all disease types in the western mountainous regions of Ethiopia. Access to high quality drinking water, a latrine, and garbage disposal, are strongly related to reduced overall morbidity levels, though not necessarily to reduced diarrhoeal disease levels.