Photocatalysis has attracted increasing scientific interest since it represents a promising path to combat the growing energy crisis and environmental pollution problems. Among the various materials used in photocatalysis, perovskites have become ideal photocatalysts due to their superior optoelectronic, morphologic, and physicochemical properties. However, pristine perovskites still have issues, such as weak stability, limited carrier extraction, and restricted active sites. Therefore, various strategies have been developed to improve the photocatalytic activity of pure perovskites in combination with other materials to form more efficient heterojunction composites. This review paper aims to report on the latest advances in the development, characterization, and photocatalytic efficiency of perovskite-based heterojunction composites coupled with binary and ternary semiconductors, carbon materials, metal oxides, and sulfides. The photocatalytic processes covered in this work are CO₂ reduction, H₂ generation, and the degradation of organic pollutants. This study is expected to intensify research on the development of perovskite-based composites and their future application to obtain chemicals of industrial interest, biofuels, and clean water with perspective at pilot and industrial scale.

Sediment microbial fuel cells (SMFC) are bioelectrochemical systems that can use different wastes for energy production. This work studied the implementation of nanoparticles (NPs) of α-FeOOH (goethite, which is well-known as a photoactive catalyst) in the electrodes of an SMFC for its potential use for dye removal. The results obtained demonstrate the feasibility of the NPs activation with the electrical potential generated in the electrodes in the SMFC instead of the activation with light. The NPs of α-FeOOH were synthesized using a hydrothermal process, and the feasibility of a conductive bio-composite (biofilm and NPs) formation was proven by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and electrochemical techniques. The improvement of the power density in the cell was more than twelve times higher with the application of the bio-composite, and it is attributed mostly to the presence of NPs. The results also demonstrate the NPs effect on the increase of the electron transfer, which resulted in 99% of the COD removal. The total electrical energy produced in 30 days in the SMFC was 1.2 kWh based on 1 m² of the geometric area of the anode. The results confirm that NPs of α-FeOOH can be used to improve organic matter removal. Moreover, the energy produced due to its activation through the potential generated between the electrodes suggests the feasibility of its implementation for dye removal.

The agricultural residue of corn cob was used as an inexpensive and abundant material for the manufacture of a green heterogeneous solid catalyst intended for the production of biodiesel from sunflower oil. The catalyst was synthesized through a straightforward calcination process at 500 °C for 3 h under ambient atmosphere. The resulting material was directly applied in the direct transesterification without further modification. The structural and physicochemical characteristics of the heterogeneous catalyst were investigated using XRD, SEM, EDS, BET, and FTIR analysis, while the alkalinity was evaluated by titration. The results revealed that the green heterogeneous catalyst consists of several active potassium phases, including KCl, K₂SO₄, K₆P₆O₁₈, K₂CO₃, and K₃AlO₃, which boost the basicity required to promote biodiesel synthesis. The catalyst reached its highest biodiesel yield (96.76%) under optimized transesterification conditions, namely 3 wt% catalyst dosage, a reaction temperature of 65 °C, a methanol-to-oil ratio of 9:1, and a transesterification time of 120 min. The catalyst was successfully reused for seven consecutive cycles while maintaining a biodiesel yield of approximately 78%. Biodiesel quality is closely compared to ASTM D6751 and EN 14,214 standards. Overall, work highlights the development of stable heterogeneous catalysts derived from inexpensive, environmentally friendly, and widely available materials, such as agricultural residue from corn cobs. Graphical abstract

En este trabajo, se elaboraron y caracterizaron nanopartículas metálicas de hematita (α-Fe2O3) sintetizadas por el método tradicional de coprecipitación seguido de un tratamiento térmico a 500 °C durante 1 hora a atmosfera ambiente, para ser empleadas como catalizador heterogéneo para la producción de biodiésel a partir del aceite de soya. Las propiedades texturales (BET) y morfológicas (SEM) de las nanopartículas indican que presentan un área superficial de 100.86 m2/g y una morfología superficial en forma de nanovarillas con abundante porosidad. El análisis XRD indico los planos (1 0 4) y (1 1 0) característicos de las nanopartículas de α-Fe2O3. El rendimiento máximo que alcanzó en la producción de biodiésel fue del 90 % bajo condiciones optimizadas. Una relación molar de metanol a aceite de soya de 15:1, con una carga de catalizador del 4 wt %, y un tiempo de reacción de 240 min. La temperatura de reacción y la agitación fueron de 65 °C y 600 rpm. El catalizador basado en nanopartículas metálicas de α-Fe2O3 puede ser reutilizado durante 7 ciclos consecutivos hasta perder su actividad catalítica. El biodiésel producido de soya cumple con los valores establecidos por la Sociedad Americana de Pruebas y Materiales (ASTM)

Ethanol production from corn and sugarcane is well established; however, reliance on these feedstocks raises concerns related to food security, highlighting the need to explore alternative raw materials such as cassava. This study evaluates bioethanol production from different cassava root fractions—peeled cassava, starch, and peel—assessed individually within a unified experimental framework. Chemical hydrolysis using HCl or H₂SO₄ was employed as a cost-effective alternative to enzymatic saccharification. Hydrolysis efficiencies above 95% were achieved for both cassava and starch, regardless of the acid used, although HCl promoted higher glucose release in all samples. Chemical hydrolysis induced noticeable increases in surface roughness and porosity across all fractions. Fermentation efficiencies for cassava (93.1 ± 1.1% vs. 77.8 ± 4.9%) and peel (85.7 ± 2.8% vs. 69.8 ± 7.4%) were higher when HCl was used during hydrolysis, whereas starch showed no significant differences between acids. In contrast, the highest ethanol yields on a dry raw material basis were obtained from cassava hydrolyzed with H₂SO₄ (up to 0.37 ± 0.002 g/g), corresponding to a 73% ethanol recovery efficiency. The highest volumetric ethanol production rates were achieved with HCl hydrolysates, reaching up to 1.85 g/L/h for peel-derived hydrolysates.

En este trabajo se sintetizaron nanopartículas de óxido de hierro (NPs-FeO) a partir de las hojas del extracto acuso de Cymbopogon citratus usando química verde. Posteriormente, las NPs-FeO fueron esparcidas sobre fieltro de carbón por la técnica de aerografía para después utilizarse como cátodo o como bioánodo. El electrodo con NPs-FeO fue colonizado con bacterias para finalmente utilizarse como bioánodo en una celda de combustible microbiana sedimetaria (SMFC, por sus siglas en ingles). Las propiedades cristalográficas, morfológicas y minerales de las NPs sintetizadas, se determinaron a través del análisis XRD, SEM y EDS. Los resultados revelaron que las NPs, presentan una estructura cristalina amorfo, con una superficie altamente porosa y una alta concentración de hierro. Se realizaron análisis de voltamperometría cíclica antes y después del crecimiento microbiano. Las pruebas en la celda de combustible microbiana sedimentaria mostraron producciones de energía de 1.46 W/m2 al emplearse el electrodo con NPs-FeO como ánodo y 0.59 W/m2 al emplearse como cátodo