Glycerol is a massive byproduct of biodiesel fabrication, which decreases its price and increases the risks of inadequate disposal. In this sense, more environmentally friendly instruments and processes using glycerol are required to make this matrix more valuable. Here, a 3D-printed electrolyzer was developed and tested for long-period glycerol electrolysis in an alkaline medium. The new electrolyzer contains only three mobile parts and can be manufactured in less than 4 h using ∼30 g of polylactic acid filament, with a total cost of less than US $5. This easily built and inexpensive reduced-scale electrolyzer has the advantage of using only a few milliliters of solution to perform tests for electrosynthesis. We synthesized Pd nanocubes to modify a glassy carbon working electrode, which was used for glycerol electrolysis. We found a remarkable selectivity of 99% toward tartronate production, which was induced by the extended (100) surface of Pd in the alkaline medium. Hence, we report a new 3D-printed platform for electrosynthesis and a new clean one-step method to produce tartronate.

Insulating printed plastics are turned into metallic pieces by electrochemical polymerization of aniline followed by metal electrodeposition.

3D-Printed microfluidic fuel cell.

The combination of a fuel cell and photocatalysis in the same device, called a photo fuel cell, is the next generation of energy converters. These systems aim to convert organic pollutants and oxidants into energy using solar energy as the driving force. However, they are mostly designed in conventional stationary batch systems, generating low power besides being barely applicable. In this context, membraneless microfluidics allows the use of flow, porous electrodes, and mixed media, improving reactant utilization and output power accordingly. Here, we report an unprecedented reusable three-dimensional (3D) printed microfluidic photo fuel cell (μpFC) assembled with low-content PtO x /Pt dispersed on a BiVO4 photoanode and a Pt/C dark cathode, both immobilized on carbon paper. We use fused deposition modeling for additive manufacturing a US$ 2.5 μpFC with a polylactic acid filament. The system shows stable colaminar flow and a short time light distance. As a proof-of-concept, we used the pollutant-model rhodamine B as fuel, and O2 in an acidic medium at the cathode side. The mixed-media 3D printed μpFC with porous electrodes produces remarkable 0.48 mW cm–2 and 4.09 mA cm–2 as maximum power and current densities, respectively. The system operates continuously for more than 5 h and converts 73.6% rhodamine by photoelectrochemical processes. The 3D printed μpFC developed here shows promising potential for pollutant mitigation concomitantly to power generation, besides being a potential platform of tests for new (photo)­electrocatalysts.

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 threedimensional (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.