A Spin Coating Method To Deposit Iridium-Based Catalysts onto Silicon for Water Oxidation Photoanodes.

Silicon has shown promise for use as a small band gap (1.1 eV) absorber material in photoelectrochemical (PEC) water splitting. However, the limited stability of silicon in acidic electrolyte requires the use of protection strategies coupled with catalysts. Herein, spin coating is used as a versatile method to directly coat silicon photoanodes with an IrOx oxygen evolution reaction (OER) catalyst, reducing the processing complexity compared to conventional fabrication schemes. Biphasic strontium chloride/iridium oxide (SrCl2:IrOx) catalysts are also developed, and both catalysts form photoactive junctions with silicon and demonstrate high photoanode activity. The iridium oxide photoanode displays a photocurrent onset at 1.06 V vs reversible hydrogen electrode (RHE), while the SrCl2:IrOx photoanode onsets earlier at 0.96 V vs RHE. The differing potentials are consistent with the observed photovoltages of 0.43 and 0.53 V for the IrOx and SrCl2:IrOx, respectively. By measuring the oxidation of a reversible redox couple, Fe(CN)63-/4-, we compare the charge carrier extraction of the devices and show that the addition of SrCl2 to the IrOx catalyst improves the silicon-electrolyte interface compared to pure IrOx. However, the durability of the strontium-containing photoanode remains a challenge, with its photocurrent density decreasing by 90% over 4 h. The IrOx photoanode, on the other hand, maintained a stable photocurrent density over this timescale. Characterization of the as-prepared and post-tested material structure via Auger electron spectroscopy identifies catalyst film cracking and delamination as the primary failure modes. We propose that improvements to catalyst adhesion should further the viability of spin coating as a technique for photoanode preparation.

Fewer immigrants have preventable ED visits in the United States.

OBJECTIVE: The aim of this study is to examine differences in having preventable emergency department (ED) visits between noncitizens, naturalized and US-born citizens in the United States. METHODS: We linked the 2008-2012 Medical Expenditure Panel Survey with National Health Interview Survey data to draw a nationally representative sample of US adults. Univariate analysis described distribution of preventable ED visits identified by the Prevention Quality Indicators across immigration status. We also assessed the association between preventable ED visits and immigration status, controlling for demographics, socioeconomic status, health service utilization, and health status. We finally applied the Oaxaca-Blinder decomposition method to measure the contribution of each covariate to differences in preventable ED services utilization between US natives, naturalized citizens, and noncitizens. RESULTS: Of US natives, 2.1% had any preventable ED visits within the past years as compared to 1.0% of noncitizens and 1.5% of naturalized citizens. Multivariate results also revealed that immigrants groups had significantly lower odds (adjusted OR: naturalized citizen 0.77 [0.61-0.96], noncitizen 0.62 [0.48-0.80]) of having preventable ED visits than natives. Further stratified analysis by insurance status showed these differences were only significant among the uninsured and public insurance groups. Race/ethnicity and health insurance explained about 68% of the difference in preventable ED service utilization between natives and noncitizens. CONCLUSION: Our study documents the existing differences in preventable ED visits across immigration status, and highlights the necessity to explore unmet health needs among immigrants and eliminate disparities.