Photovoltaic Electrochemically Driven Degradation of Calcon Dye with Simultaneous Green Hydrogen Production.

In this study, for the first time, the production of green hydrogen gas (H2) in the cathodic compartment, in concomitance with the electrochemical oxidation (EO) of an aqueous solution containing Calcon dye at the anodic compartment, was studied in a PEM-type electrochemical cell driven by a photovoltaic (PV) energy source. EO of Calcon was carried out on a Nb/BDD anode at different current densities (7.5, 15 and 30 mA cm-2), while a stainless steel (SS) cathode was used for green H2 production. The results of the analysis by UV-vis spectroscopy and total organic carbon (TOC) clearly showed that the electrochemical oxidation (EO) of the Calcon dye after 180 min of electrolysis time by applying 30 mA cm-2 reached up to 90% of degradation and 57% of TOC removal. Meanwhile, under these experimental conditions, a green H2 production greater than 0.9 L was achieved, with a Faradaic efficiency of 98%. The hybrid electrolysis strategy is particularly attractive in the context of a circular economy, as these can be coupled with the use of more complex water matrices to transform organic depollution into an energy resource to produce H2 as a chemical energy carrier.

Group Emotion Detection Based on Social Robot Perception.

Social robotics is an emerging area that is becoming present in social spaces, by introducing autonomous social robots. Social robots offer services, perform tasks, and interact with people in such social environments, demanding more efficient and complex Human-Robot Interaction (HRI) designs. A strategy to improve HRI is to provide robots with the capacity of detecting the emotions of the people around them to plan a trajectory, modify their behaviour, and generate an appropriate interaction with people based on the analysed information. However, in social environments in which it is common to find a group of persons, new approaches are needed in order to make robots able to recognise groups of people and the emotion of the groups, which can be also associated with a scene in which the group is participating. Some existing studies are focused on detecting group cohesion and the recognition of group emotions; nevertheless, these works do not focus on performing the recognition tasks from a robocentric perspective, considering the sensory capacity of robots. In this context, a system to recognise scenes in terms of groups of people, to then detect global (prevailing) emotions in a scene, is presented. The approach proposed to visualise and recognise emotions in typical HRI is based on the face size of people recognised by the robot during its navigation (face sizes decrease when the robot moves away from a group of people). On each frame of the video stream of the visual sensor, individual emotions are recognised based on the Visual Geometry Group (VGG) neural network pre-trained to recognise faces (VGGFace); then, to detect the emotion of the frame, individual emotions are aggregated with a fusion method, and consequently, to detect global (prevalent) emotion in the scene (group of people), the emotions of its constituent frames are also aggregated. Additionally, this work proposes a strategy to create datasets with images/videos in order to validate the estimation of emotions in scenes and personal emotions. Both datasets are generated in a simulated environment based on the Robot Operating System (ROS) from videos captured by robots through their sensory capabilities. Tests are performed in two simulated environments in ROS/Gazebo: a museum and a cafeteria. Results show that the accuracy in the detection of individual emotions is 99.79% and the detection of group emotion (scene emotion) in each frame is 90.84% and 89.78% in the cafeteria and the museum scenarios, respectively.

Applicability of Cork as Novel Modifiers to Develop Electrochemical Sensor for Caffeine Determination.

This study aims to investigate the applicability of a hybrid electrochemical sensor composed of cork and graphite (Gr) for detecting caffeine in aqueous solutions. Raw cork (RAC) and regranulated cork (RGC, obtained by thermal treatment of RAC with steam at 380 °C) were tested as modifiers. The results clearly showed that the cork-graphite sensors, GrRAC and GrRGC, exhibited a linear response over a wide range of caffeine concentration (5-1000 µM), with R2 of 0.99 and 0.98, respectively. The limits of detection (LOD), estimated at 2.9 and 6.1 µM for GrRAC and GrRGC, suggest greater sensitivity and reproducibility than the unmodified conventional graphite sensor. The low-cost cork-graphite sensors were successfully applied in the determination of caffeine in soft drinks and pharmaceutical formulations, presenting well-defined current signals when analyzing real samples. When comparing electrochemical determinations and high performance liquid chromatography measurements, no significant differences were observed (mean accuracy 3.0%), highlighting the potential use of these sensors to determine caffeine in different samples.

Degradation of 1-hydroxy-2,4-dinitrobenzene from aqueous solutions by electrochemical oxidation: role of anodic material.

Electrochemical oxidation (ECOx) of 1-hydroxy-2,4-dinitrobenzene (or 2,4-dinitrophenol: 2,4-DNP) in aqueous solutions by electrolysis under galvanostatic control was studied at Pb/PbO2, Ti/SnO2, Ti/IrxRuySnO2 and Si/BDD anodes as a function of current density applied. Oxidative degradation of 2,4-DNP has clearly shown that electrode material and the current density applied were important parameters to optimize the oxidation process. It was observed that 2,4-DNP was oxidized at few substrates to CO2 with different results, obtaining good removal efficiencies at Pb/PbO2, Ti/SnO2 and Si/BDD anodes. Trends in degradation way depend on the production of hydroxyl radicals (OH) on these anodic materials, as confirmed in this study. Furthermore, HPLC results suggested that two kinds of intermediates were generated, polyhydroxylated intermediates and carboxylic acids. The formation of these polyhydroxylated intermediates seems to be associated with the denitration step and substitution by OH radicals on aromatic rings, this being the first proposed step in the reaction mechanism. These compounds were successively oxidized, followed by the opening of aromatic rings and the formation of a series of carboxylic acids which were at the end oxidized into CO2 and H2O. On the basis of these information, a reaction scheme was proposed for each type of anode used for 2,4-D oxidation.