We report a facile hydrothermal method for the synthesis of niobium pentoxide (Nb2O5) under two different temperatures, 120 °C (Nb2O5-120) and 150 °C (Nb2O5-150). The obtained materials were characterized by structural, optical and morphological techniques. Also, the photocatalytic properties of the Nb2O5 samples were evaluated in two reactions under ultraviolet (UVC) irradiation: degradation of methylene blue (MB) and indigo carmine (IC) dyes; and esterification of free fatty acids (FFA) present in waste cooking oil (WCO). The Nb2O5 was formed at different temperatures of synthesis, and the increase in temperature did not cause significant changes in the structural and optical characteristics, but resulted in an increased surface area of the synthesized materials. Both synthesized materials showed excellent efficiency for dye photodegradation. The sample Nb2O5-150 presented the best performance for the MB photodegradation, with almost 85% of the removal efficiency. In this case, the adsorption of MB molecules on the surface of the material was high due to the favorable electrostatic interaction and also because of its high surface area. For the IC photodegradation, the adsorption was insignificant, and both samples presented approximately 100% of the removal efficiency. These materials were also promising for the reduction of free fat acids in waste oil by photoesterification. NbO Nb O (Nb2O5 12 C Nb2O5120 (Nb2O5-120 15 Nb2O5150. Nb2O5150 . (Nb2O5-150) techniques Also Nb2O UVC (UVC irradiation (MB (IC dyes FFA (FFA WCO. WCO (WCO) characteristics photodegradation Nb2O5-15 85 case insignificant 100 photoesterification (Nb2O 1 Nb2O512 (Nb2O5-12 Nb2O515 (Nb2O5-150 (WCO Nb2O5-1 8 10 Nb2O51 (Nb2O5-1 (Nb2O5-15 Nb2O5- (Nb2O5-

Proton exchange membrane water electrolysis (PEMWE) performs the electrolysis of water to produce hydrogen, a source of clean and renewable energy. The most used commercial electrolyte in PEMWE is the Nafion membrane, a material that is expensive and difficult to recycle. The partial replacement of Nafion with cellulose nanocrystals (CNCs) can produce composite membranes can increased electrical, mechanical and biodegradability properties. In this sense, the objective of this work is to study the elaboration of nanocomposites (Nafion-CNC) aiming at developing high-performance electrolytes for application in PEMWE. The effects of adding CNCs to Nafion were evaluated. Nafion membranes were produced with two types of CNCs, one obtained by enzymatic hydrolysis and the other by acid hydrolysis (commercial). The addition of both CNCs has similar effects on Nafion's properties. For samples with both commercial and enzymatic CNC, an increase in the modulus of elasticity (10% and 40% respectively) and maximum stress (10% and 13% respectively) was observed. The two nanocomposites showedlower initial thermal degradation temperatures, however, they still showed sufficient stability (Tonset gt; 170°C) for application in PEMWE (standard operating temperature lt;100°C). Furthermore, there was a significant increase in the humidification capacity and increase in conductivity. Composite membranes were tested in PEMWE and their usability was proven.

La electrólisis del agua con membrana de intercambio de protones (PEMWE) realiza la electrólisis del agua para producir hidrógeno, una fuente de energía limpia y renovable. El electrolito comercial más utilizado en PEMWE es la membrana Nafion, un material caro y difícil de reciclar. El reemplazo parcial de Nafion con nanocristales de celulosa (CNC) puede producir membranas compuestas que pueden aumentar las propiedades eléctricas, mecánicas y de biodegradabilidad. En este sentido, el objetivo de este trabajo es estudiar la elaboración de nanocompositos (Nafion-CNC) con el objetivo de desarrollar electrolitos de alto rendimiento para su aplicación en PEMWE. Se evaluaron los efectos de agregar CNC a Nafion. Las membranas de Nafion se produjeron con dos tipos de CNC, uno obtenido por hidrólisis enzimática y el otro por hidrólisis ácida (comercial). La adición de ambos CNC tiene efectos similares en las propiedades de Nafion. Para muestras con CNC tanto comerciales como enzimáticas, se observó un aumento en el módulo de elasticidad (10% y 40% respectivamente) y tensión máxima (10% y 13% respectivamente). Los dos nanocompuestos mostraron temperaturas iniciales de degradación térmica más bajas, sin embargo, aún mostraron suficiente estabilidad (Tonset gt; 170 °C) para su aplicación en PEMWE (temperatura de operación estándar lt;100 °C). Además, hubo un aumento significativo en la capacidad de humidificación y un aumento en la conductividad. Las membranas compuestas se probaron en PEMWE y se comprobó su usabilidad.

A eletrólise da água com membrana de troca de prótons (PEMWE) realiza a eletrólise da água para produzir hidrogênio, uma fonte de energia limpa e renovável. O eletrólito comercial mais utilizado no PEMWE é a membrana de Nafion, um material caro e de difícil reciclagem. A substituição parcial do Nafion por nanocristais de celulose (CNCs) pode produzir membranas compostas com propriedades elétricas, mecânicas e de biodegradabilidade aumentadas. Nesse sentido, o objetivo deste trabalho é estudar a elaboração de nanocompósitos (Nafion-CNC) visando o desenvolvimento de eletrólitos de alto desempenho para aplicação em PEMWE. Os efeitos da adição de CNCs ao Nafion foram avaliados. As membranas de nafion foram produzidas com dois tipos de CNCs, um obtido por hidrólise enzimática e outro por hidrólise ácida (comercial). A adição de ambos os CNCs tem efeitos semelhantes nas propriedades do Nafion. Para amostras com CNC comercial e enzimática, observou-se um aumento no módulo de elasticidade (10% e 40% respectivamente) e tensão máxima (10% e 13% respectivamente). Os dois nanocompósitos apresentaram menores temperaturas iniciais de degradação térmica, porém, ainda apresentaram estabilidade suficiente (Tonset gt; 170°C) para aplicação em PEMWE (temperatura padrão de operação lt;100°C). Além disso, houve um aumento significativo na capacidade de umidificação e aumento na condutividade. As membranas compostas foram testadas em PEMWE e sua usabilidade foi comprovada.