Hybrid Photocathode Research Articles

Continuous Flow Photoelectrochemical Reactor for Solar Conversion of Carbon Dioxide to Alcohols

A newly-designed continuous flow photoelectrochemical reactor (CFPR) was applied to the solar photoelectrosynthesis of alcohols from carbon dioxide (CO2) dissolved in aqueous media. Hybrid p-type CuO/Cu2O semiconductor nanorod arrays, prepared by a three-step synthesis method (sol-gel synthesis, thermal anneal, and cathodic electrodeposition) were used as photocathodes. Scanning electron microscopy and powder X-ray diffraction were used to characterize these hybrid materials at various stages of the preparation protocol as well as before and after being subjected to photoelectrolysis for selected periods of time. The performance of the CFPR with the hybrid photocathode was analyzed in CO2-saturated aqueous bicarbonate solution at −0.3 V vs Ag/AgCl under simulated AM 1.5 solar irradiation for periods up to 5 h. The hybrid photocathode formulation facilitated efficient photoelectron injection to CO2 while its robustness and high photoelectrochemically active surface area enhanced the formation of alcohols. Gas chromatographic analyses of the photoelectrolysis solutions under a flow rate of 5 ml/h revealed ethanol to be the main product followed by isopropanol and methanol. The amounts of alcohol assayed indicated a faradaic efficiency ranging from 75 to 96%. The formation of C-C bonds in the products is a significant finding in this study and a mechanistic hypothesis is presented to account for products such as ethanol instead of methanol as is usually seen. Finally, the CFPR performance was numerically simulated to unravel the influence of flow rate and channel geometry on CO2 conversion and consumption rate.

Engineering a Cu2O/NiO/Cu2MoS4 hybrid photocathode for H2 generation in water.

We report a scalable process for fabricating a multiple-layer hybrid photocathode, namely Cu2O/NiO/Cu2MoS4, for H2 generation in water. In pH 5 solution and under 1 sun illumination, the photocathode showed interesting photocatalytic properties. The onset photocurrent was recorded at +0.45 V vs. RHE, while at 0 V vs. RHE, a photocurrent density of 1.25 mA cm(-2) was obtained. It was found that the NiO interlayer enhances charge transfer from the Cu2O light harvester to the Cu2MoS4 hydrogen evolution reaction electrocatalyst which in turn accelerates charge transfer at the electrode/electrolyte interface, and therefore improves the photocatalytic properties of the Cu2O photocathode.

Solar CO2 reduction using H2O by a semiconductor/metal-complex hybrid photocatalyst: enhanced efficiency and demonstration of a wireless system using SrTiO3 photoanodes

Solar formate production from CO2 and H2O was achieved with no external electrical bias by combining an InP/[RuCP] semiconductor/metal-complex hybrid photocathode with a reduced SrTiO3 (r-STO) photoanode. The conversion efficiency from solar to chemical energy was improved from 0.03 to 0.14% compared to a previous system utilizing a TiO2 photoanode. Stimulated electron transfer from the photoanode to the photocathode is the main cause for the observed improvement, due to an enlarged difference in the band-energy position between r-STO and InP. Since r-STO showed high H2O oxidation selectivity even in the presence of formate, a r-STO/InP/[RuCP] wireless device successfully performed solar CO2 reduction in a one-compartment reactor with no proton exchange membrane, yielding a solar conversion efficiency of 0.08%.

New Generations of Position Sensitive Silicon Detectors

AbstractThe new generation of elementary particle and nuclear physics experiments demand instrumentation with a more precise spatial resolution and a better and faster energy response. Nuclear physics and space experiments need position sensitive pad detectors having very thin entrance windows while high energy physics and medical applications use fast microstrip or drift detectors. Silicon pixel detectors can be improved by implementing integrated electronics on it. They allow a better X-ray energy resolution and are also used in hybrid photocathode tubes for faster timing and larger dynamic range.