Nowadays, Sn-based electrocatalysts for the electrochemical CO2 reduction reaction (eCO2RR) toward formic acid have been reported to reach industrially relevant current densities and Faradaic efficiencies approaching 100%. However, electrocatalyst stability remains inadequate and appears to be a crucial piece to the puzzle, as lifetimes in the range of several thousands of hours should be reached for practical application and economic viability. Here, we provide insights into stability issues related to Sn-based electrocatalysts and electrolyzers for formic acid production. By determining the chemical and physical phenomena that occur during the electrochemical reduction reaction on the surface and bulk of Sn-based catalysts, we intend to elucidate the most common degradation mechanisms that impair long-term electrocatalytic activity of these catalysts. Moreover, highlighting the importance of correctly selected process conditions and an optimized reactor design allows us to unveil all necessary aspects for a stable Sn-based eCO2RR toward formic acid.

Here, we combine CO₂ laser heating and an ionic liquid solvent (i.e., methylimidazolium hydrogensulfate HMIM⁺ HSO₄^–) as an innovative route to produce Ti/Ru_0.3Ti_0.7O₂ anodes. For comparison purposes, the anodes were also prepared using conventional thermal treatment (in a furnace), and by the standard polymeric precursor method (also known as the Pechini method). For the laser heating, the anodes were heated at a power density of 0.4 W mm⁻² up to 550 °C and kept at this temperature for 40 s, followed by instantaneous cooling. Using these conditions, the total time spent to produce an anode (considering cooling) is just 9.7 min. It represents a remarkable reduction in 446-fold and 359-fold when compared with the conventional heating for Pechini and IL methods, respectively. The laser-prepared anodes presented an increase of 63.4% and 53.8% in the voltammetric charge, while the charge transfer resistance decreases 9.6-fold and 17.3-fold using IL and Pechini methods, respectively, when compared with their correspondent furnace-made ones. Finally, superior electrocatalytic activity toward the removal of the model pollutant atrazine is observed for the laser-prepared anodes. The anode produced using laser and the IL method is the most efficient, removing 81% of atrazine in 60 min, and presents the highest kinetic rate (0.062 min⁻¹) at the lowest energy consumption (0.179 kWh L^–1). The excellent electrocatalytic response of the anodes innovatively synthesized in this study characterizes them as an encouraging advance in the search for efficient materials to be applied in the electrochemical oxidation of organic compounds.

SnO2-Based materials have attracted much attention in the electrochemical oxidation field due to their high electrocatalytic activity. However, efforts are still required to improve their physical and electrochemical properties. Here we employed a CO2 laser thermal process, as a substitute to conventional furnace heating, for the synthesis of two SnO2-based anodes-Ti/SnO2-Sb2O5 and Ti/SnO2-Sb-La2O3. Compared with anodes made using conventional heating, the laser-prepared anodes show a more compact surface and a change from hydrophilic to super-hydrophobic wetting properties. Energy-dispersive X-ray spectroscopy and X-ray diffraction data reveal the uniform distribution of Sn, Sb, and La, as well as the formation of the desired oxides, respectively. The oxidation state and chemical composition were confirmed by X-ray photoelectron spectroscopy. Notably, the laser-prepared anodes exhibit a positive shift in the oxygen evolution overpotential, especially for the Ti/SnO2-Sb-La2O3 anode, and a 2-fold reduction in the charge transfer resistance. The electrochemical degradation of 4-nitrophenol (4-NP) was investigated in aqueous solutions by UV-Vis spectra employing all anodes produced. The results showed that laser-prepared Ti/SnO2-Sb-La2O3 displays the highest degradation efficiency at the lowest energy consumption. Also, a mechanism for the 4-NP oxidation at the SnO2-based anodes under the current working conditions is proposed. Finally, the notable reduction in processing time and energy spent using laser heating makes it a feasible alternative to produce SnO2-based anodes. Their improved properties enhance the potential of these anodes to be applied in the electrochemical treatment of polluted waters.

The electrochemical reduction of CO₂ to fuels or commodity chemicals is a reaction of high interest for closing the anthropogenic carbon cycle. The role of the electrolyte is of particular interest, as the interplay between the electrocatalytic surface and the electrolyte plays an important role in determining the outcome of the CO₂ reduction reaction. Therefore, insights on electrolyte effects on the electrochemical reduction of CO₂ are pivotal in designing electrochemical devices that are able to efficiently and selectively convert CO₂ into valuable products. Here, we provide an overview of recently obtained insights on electrolyte effects and we discuss how these insights can be used as design parameters for the construction of new electrocatalytic systems.