CO2 REDUCTION TO HYDROCARBONS AND OXYGENATES: FUNDAMENTALS, STRATEGIES AND CHALLENGES. The development of renewable energy sources (e.g., solar and wind) moves foward, the tendance for replacing fossil fuels increases. However, these technologies have as primary barriers to industrial processes’ efficiency and especially storage. Thus, CO2 reduction routes using these energy sources could chemically store part of the energy as fuels or chemicals, offering alternatives to current oil and gas industry. This process is inspired by photosynthesis, e.g., photochemical or electrochemical processes, using homogeneous or heterogeneous catalysts. Nevertheless, this reaction is thermodynamically unfavorable and has very slow kinetics, given the high stability of the CO2 molecule and the complexity of the redox reactions involved. Therefore, this review addresses this process’s kinetic and thermodynamic challenges, and the fundamental concepts of the photo(electro)chemical processes for CO2 reduction, besides presenting and discussing the materials with the potential to act as catalysts. The main reaction mechanisms and advances in the understanding of such processes are discussed, as well as future perspectives

Heterostructured semiconductors are materials with unique features formed by combination of two or more semiconductors with suitable interface between them. The study of the heterostructures aim the development of physico-chemical and photocatalytic properties higher than their isolated phases, which makes it possible to obtain higher efficiency and lower cost in several technological processes. Recently the heterostructured materials have been extensively used in the development of alternative technologies either for environmental pollution control or for renewable energy production, among other applications. However, the obtaining of a heterostructure with suitable features is not trivial. In this way, this review article presents a broad discussion about methods of obtaining heterostructures formed by semiconductors and their applications in the photochemical processes, mainly in the environmental field. It will be addressed the use of the heterostructures in photocatalytic application for the organic pollutants degradation, heavy metals removal, the inactivation of pathogenic microorganisms, beyond of the volatile organic compounds (VOC’s) photooxidation and the photocatalytic abatement of nitrogen oxide (NOx) in gaseous phase. Finally, a discussion about the carbon dioxide (CO2) photoreduction and hydrogen (H2) production focusing mainly in the chemical energy production will be presented.

Formicidae é um grupo abundante no solo e também largamente distribuído em todos os estratos da vegetação, constituindo-se em um bom modelo biológico para estudos de estratificação vertical. O objetivo geral do trabalho foi determinar os padrões de estratificação da assembléia de formigas em três estratos verticais (solo, estrato arbustivo e estrato arbóreo). Os dados foram coletados no Parque Estadual da Serra de Caldas Novas, em uma área de cerrado strictu sensu. A coleta de formigas foi realizada utilizando-se armadilhas do tipo pitfall. Foram instaladas 11 armadilhas no solo, 17 em plantas do estrato arbustivo e 23 em plantas do estrato arbóreo (uma armadilha por planta). Foi coletado um total de 49 espécies de formigas, pertencentes a 15 gêneros e cinco subfamílias. Através de curvas de acumulação de espécies, pôde-se verificar que existem 37,5% a mais de espécies no solo do que nas árvores e 35% a mais de espécies nas árvores do que nos arbustos. Uma análise de agrupamento indicou uma similaridade mediana entre as espécies de formigas do solo e vegetação (estrato arbustivo e arbóreo). Uma análise de aninhamento demonstrou que as espécies presentes no solo são um subconjunto das espécies presentes nos dois estratos de vegetação. Mesmo sem uma estratificação vertical muito clara, a alta diversidade de formigas encontrada no cerrado pode ser explicada em parte pelo fato de algumas espécies serem especializadas em forragear e/ou nidificar no solo e outras na vegetação.

Formicidae is an abundant group in the soil and is also well distributed in all vegetation strata, representing a good model for studies on vertical stratification of the fauna. The aim of this study was to verify a possible stratification of ant assemblages inhabiting the soil, the lower and the higher vegetation strata. Data was collected in the Serra de Caldas Novas State Park, in an area of cerrado strictu sensu. Ant collection was performed using pitfall traps. A total of 11 traps were placed in the soil, 17 in the lower vegetation stratum (dominated by shrubs and small trees) and 23 in the higher vegetation stratum (dominated by taller, mature trees). Forty-nine species of ants from 15 genera and five subfamilies were collected. Accumulation curves indicated that there is 37.5% more species in the soil than in mature trees and 35% more species in mature trees than in shrubs/young trees. There was not a clear vertical stratification between the soil and the two vegetation strata. Therefore, the species present in the vegetation tended to represent a nested subset of those found in the soil. Even without a clear vertical stratification, the diversity of ants in the cerrado vegetation is high, and part of this diversity appears to be explained by the fact that some species are specialized in nesting and/or foraging in the soil, while others in the vegetation.

Poucos estudos avaliaram a eficiência de métodos para a coleta de formigas, especialmente em regiões com fisionomias vegetais bastante variáveis como a do Cerrado. Neste trabalho, foram comparados três métodos para a coleta de formigas do solo: armadilhas de solo, iscas de sardinha e o extrator de serapilheira de Winkler, com o objetivo de determinar o mais apropriado para caracterizar as assembléias de formigas associadas a diferentes tipos de vegetação. Mais espécies foram coletadas com armadilhas de solo e com o extrator de Winkler do que com iscas. As armadilhas de solo coletaram mais espécies nas fisionomias de cerrado (savânicas), particularmente naquelas com pobre cobertura de serapilheira, enquanto o extrator de Winkler foi mais eficiente nas fisionomias florestais, com exceção daquela sujeita a inundações periódicas. Houve baixa similaridade na composição de espécies entre as fisionomias de cerrado e florestais, e esse padrão foi observado com qualquer dos três métodos de coleta. Portanto, mesmo o uso de um único método pode ser suficiente em estudos que comparam condições ou hábitats bastante distintos. Entretanto, se o propósito da amostragem for produzir um inventário mais completo, sugerimos o uso de uma combinação de métodos, em particular as armadilhas de solo e o extrator de Winkler. Desse modo, o Protocolo para Amostragem de Formigas da Serapilheira (ALL Protocol) parece ser adequado para a amostragem de formigas na ameaçada região do Bioma Cerrado.

Few studies have evaluated the efficiency of methods for sampling ants, especially in regions with highly variable vegetation physiognomies such as the Cerrado region of central Brazil. Here we compared three methods to collect ground-dwelling ants: pitfall traps, sardine baits, and the Winkler litter extractor. Our aim was to determine which method would be most appropriate to characterize the ant assemblages inhabiting different vegetation types. More species were collected with pitfall traps and with the Winkler extractor than with sardine baits. Pitfall traps collected more species in the cerrado (savanna) physiognomies, particularly in those with a poor litter cover, whereas the Winlker extractor was more efficient in the forest physiognomies, except the one subject to periodic inundations. There was a low similarity in species composition between forest and cerrado physiognomies, and this pattern was detected regardless of the method used to sampling ants. Therefore, even the use of a single, relatively selective method of collection can be enough for studies comparing highly distinct habitats and/or conditions. However, if the purpose of the sampling is to produce a more thoroughly inventory of the ant fauna, we suggest the use of a combination of methods, particularly pitfall traps and the Winkler extractor. Therefore, the Ants of the Leaf-Litter (ALL) Sampling Protocol appear to be an adequate protocol for sampling ants in the highly-threatened Brazilian cerrado biome.