Our latest publications!

March, 2023

Paper batteries are self-pumping emerging tools for powering portable analytical systems. These disposable energy converters must be low-cost and must achieve enough energy to power electronic devices. The challenge is reaching high energy while keeping the low cost. Here, for the first time, we report a paper-based microfluidic fuel cell (PμFC) equipped with Pt/C on a carbon paper (CP) anode and a metal-free CP cathode fed by biomass-derived fuels to deliver high power. The cells were engineered in a mixed-media configuration, where methanol, ethanol, ethylene glycol, or glycerol is electro-oxidized in an alkaline medium, while Na2S2O8 is reduced in an acidic medium. This strategy allows for optimizing each half-cell reaction independently. The colaminar channel of the cellulose paper was chemically investigated by mapping the composition, which reveals a majority of elements from the catholyte and anolyte on each respective side and a mixture of both at the interface, assuring the existing colaminar system. Moreover, the colaminar flow was studied by investigating the flow rate by considering recorded videos for the first time. All PμFCs show 150–200 s to build a stable colaminar flow, which matches the time to reach a stable open circuit voltage. The flow rate is similar for different concentrations of methanol and ethanol, but it decreases with the increase in ethylene glycol and glycerol concentrations, suggesting a longer residence time for the reactants. The cells perform differently for the different concentrations, and their limiting power densities are composed of a balance among anode poisoning, residence time, and viscosity of the liquids. The sustainable PμFCs can be interchangeably fed by the four biomass-derived fuels to deliver ∼2.2–3.9 mW cm–2. This allows choosing the proper fuel due to their availability. The unprecedented PμFC fed by ethylene glycol delivered 6.76 mW cm–2, which is the benchmark output power for a paper battery fed by alcohol.

May, 2022 - Reading highlight

The combination of energy and chemical conversion can be achieved by designing glycerol fuel cells. However, the anode must promote the reaction at onset potentials low enough to allow a spontaneous reaction, when coupled to the cathodic reaction, and must be selective. Here, we build a three-dimensional (3D)-printed glycerol microfluidic fuel cell that produces power concomitantly to glycolate and formate at zero bias. The balance between energy and the two carbonyl compounds is tuned by decorating the Pt/C/CP anode in situ (before feeding the cell reactants) or in operando (while feeding the cell with reactants) with Bi. The Bi-modified anodes improve glycerol conversion and output power while decreasing the formation of the carbonyl compounds. The in operando method builds dendrites of rodlike Bi oxides that are inactive for the anodic reaction and cover active sites. The in situ strategy promotes homogeneous Bi decoration, decreasing activation losses, increasing the open-circuit voltage to 1.0 V, and augmenting maximum power density 6.5 times and the glycerol conversion to 72% at 25 °C while producing 0.2 mmoL L-1 of glycolate and formate (each) at 100 μL min-1. Such a performance is attributed to the low CO poisoning of the anode, which leads the glycerol electrooxidation toward a more complete reaction, harvesting more electrons at the device. Printing the microfluidic fuel cell takes 23 min and costs ∼US$1.85 and can be used for other coupled reactions since the methods of modification presented here are applied to any existing and assembled systems.

June, 2022

The production of 3D graphene-based materials is an alternative to retain the intrinsic properties of 2D graphene, and improve others like specific surface area, porosity, mechanical properties, etc. For practical applications such as electrochemical sensors, the production of electroactive 3D graphene-based composites in one single step with good processability and electrochemical response is extremely desirable. Here, we synthesize 3D composites of crumpled graphene (CG) decorated by copper-based nanoparticles in dry state form without further steps. The aerosol-assisted capillary compression strategy adopted results in copper-based nanoparticles directly connected to CG. The carbon nanostructure controls the nucleation and growth of nanoparticles during capillary compression. We explored the application of the composites as an electrochemical sensor for hydrogen peroxide, and it connects the best performance to the synergism between crumpled graphene and the copper-based nanoparticles.

June, 2022

The world is facing a massive problem regarding the reduction of greenhouse gases emission to the atmosphere allied to the need for new and renewable energy sources. Photocatalytic fuel cells (PFCs) have been proposed as a pathway to reduce the costs of conventional fuel cells (FCs) by designing new and smart semiconductor materials for harvesting solar energy and concomitantly converting chemical energy directly into electricity with zero carbon emissions. A PFC combines two well-defined approaches for clean energy production and fuel generation, the FCs and photoelectrochemical (PEC) systems. Regardless of being new, the PFC community is growing fast, with several papers published and patents required in the literature in the last years. We present herein a tutorial review containing the most important definitions, working principles, theoretical fundaments, and hands-on on building devices and testing half-cell reactions and performance of PFCs. In addition, for the first time, we review the recent developments of batch and microfluidic PFCs, highlighting and critically discussing the pros and cons of each approach for solar energy conversion into electricity and environmental remediation.

July, 2021

Sensors based on 3D-printed pieces made with conductive filaments are promising to decrease the cost and time of analysis. However, the conductivity of these sensors is lower than that necessary for electrochemical detection, requiring postprinting treatment. Considering that the post-treatment is mandatory to date, we used an electrochemical surface modification to convert an insulating plastic into a conductive material, eliminating the need for using a conductive filament. We used cyclic voltammetry to grow polyaniline on a polylactic acid surface in the presence of graphite (GR) in the form of trails. This simple step built a monolithic 3D-printed sensor integrated with a GR working electrode (WE). Such a sensor coupled to a minipotentiostat was used to detect caffeine by chronoamperometry in an aqueous solution with a limit of detection of 57.7 μmol L-1. We also electrodeposited Ru and Cu on the WEs, which were used for H2O2 and glucose sensing with the detection limited to 2.3 and 49.3 μmol L-1, respectively. This technique can be applied to any existing plastic object to manufacture integrated (all-in-one), stable, low-cost, and disposable sensors.

April, 2021

In this work we prepare Pd (1 0 0) preferentially oriented nanoparticles modified with different amounts of Tl and study the CO electro-oxidation reaction on these surfaces in alkaline medium. The analysis is based on cyclic voltammetry coupled with in situ FTIR spectroscopy, and the results are interpreted with the help of a DFT study. In situ FTIR indicates a change in the CO adsorption geometry on Pd surfaces partially covered by Tl, while DFT data reveal that for high Tl coverages CO adsorption is completely inhibited. Based on our findings, by using the proper amount of Tl, one can think in the development of Pd-based catalysts designed to present tolerance to CO poisoning, aiming their application in the electro-oxidation of small organic molecules.

January, 2021

Here we present a planar polydimethylsiloxane (PDMS)-based millifluidic device in which the channel (at a serpentine-shape) and a new design of electrochemical sensor (dual-mode detection) are assembled into a single chip. The platform makes use of a fully integrated reservoir to place the reference electrode, separating it from the flowing stream. The device was properly characterized aiming to evaluate the influences of channel geometries and diameters, and the electrochemical properties were improved compared with the classical reference electrode configuration. To investigate the applicability of the proposed millifluidic device, amperometric detection was used for the analysis of tap and lake water as well as groundwater samples to determine salicylic acid - selected as a model analyte. Our experimental results have demonstrated a successful prospect as amperometric detection in PDMS-based chip and showed high tolerance to disturbance by external action provided in the use of electronic micropipette and no surface inactivation from sample-interference.