Characterization of microbial fuel cells at microbially and electrochemically meaningful time scales.

The variable biocatalyst density in a microbial fuel cell (MFC) anode biofilm is a unique feature of MFCs relative to other electrochemical systems, yet performance characterizations of MFCs typically involve analyses at electrochemically relevant time scales that are insufficient to account for these variable biocatalyst effects. This study investigated the electrochemical performance and the development of anode biofilm architecture under different external loadings, with duplicate acetate-fed single-chamber MFCs stabilized at each resistance for microbially relevant time scales. Power density curves from these steady-state reactors generally showed comparable profiles despite the fact that anode biofilm architectures and communities varied considerably, showing that steady-state biofilm differences had little influence on electrochemical performance until the steady-state external loading was much larger than the reactor internal resistance. Filamentous bacteria were dominant on the anodes under high external resistances (1000 and 5000 Ω), while more diverse rod-shaped cells formed dense biofilms under lower resistances (10, 50, and 265 Ω). Anode charge transfer resistance decreased with decreasing fixed external resistances, but was consistently 2 orders of magnitude higher than the resistance at the cathode. Cell counting showed an inverse exponential correlation between cell numbers and external resistances. This direct link of MFC anode biofilm evolution with external resistance and electricity production offers several operational strategies for system optimization.

Functional materials for sustainable energy technologies: four case studies.

The critical topic of energy and the environment has rarely had such a high profile, nor have the associated materials challenges been more exciting. The subject of functional materials for sustainable energy technologies is demanding and recognized as a top priority in providing many of the key underpinning technological solutions for a sustainable energy future. Energy generation, consumption, storage, and supply security will continue to be major drivers for this subject. There exists, in particular, an urgent need for new functional materials for next-generation energy conversion and storage systems. Many limitations on the performances and costs of these systems are mainly due to the materials' intrinsic performance. We highlight four areas of activity where functional materials are already a significant element of world-wide research efforts. These four areas are transparent conducting oxides, solar energy materials for converting solar radiation into electricity and chemical fuels, materials for thermoelectric energy conversion, and hydrogen storage materials. We outline recent advances in the development of these classes of energy materials, major factors limiting their intrinsic functional performance, and potential ways to overcome these limitations.

Analysis of biodiesel and biodiesel-petrodiesel blends by high performance thin layer chromatography combined with easy ambient sonic-spray ionization mass spectrometry.

High performance thin layer chromatography (HPTLC) combined with on-spot detection and characterization via easy ambient sonic-spray ionization mass spectrometry (EASI-MS) is applied to the analysis of biodiesel (B100) and biodiesel-petrodiesel blends (BX). HPTLC provides chromatographic resolution of major components whereas EASI-MS allows on-spot characterization performed directly on the HPTLC surface at ambient conditions. Constituents (M) are detected by EASI-MS in a one component-one ion fashion as either [M + Na](+) or [M + H](+). For both B100 and BX samples, typical profiles of fatty acid methyl esters (FAME) detected as [FAME + Na](+) ions allow biodiesel typification. The spectrum of the petrodiesel spot displays a homologous series of protonated alkyl pyridines which are characteristic for petrofuels (natural markers). The spectrum for residual or admixture oil spots is characterized by sodiated triglycerides [TAG + Na](+). The application of HPTLC to analyze B100 and BX samples and its combination with EASI-MS for on-spot characterization and quality control is demonstrated.