Ammonia (NH₃) is vital for synthesizing fertilizers and has gained great attention as a carbon-free hydrogen carrier and a hydrogen-rich fuel. Electrochemical ammonia synthesis from nitrate in a water-fed polymer electrolyte membrane electrolyzer is an innovative approach to wastewater treatment. However, the major hurdles to practical implementation are competing hydrogen evolution reactions (HERs) and constrained catalytic efficiency. Herein, we demonstrate the use of polyvinylpyrrolidone (PVP)-modified ruthenium (Ru) nanoparticles as a strategy to drive the desired reaction of nitrate to ammonia. The particle size of Ru was controlled by PVP, enhancing the metal-utilization efficiency and the electrochemical active surface area. PVP modification was found to alter the electron density on Ru, suppressing the HER by increasing the energy barrier of hydrogen coupling to form H₂, while promoting absorbed hydrogen (H*) formation, facilitating the hydrogenation of intermediates to ammonia. Benefiting from the combined effects, PVP-10 wt % Ru/C achieved an ammonia production rate of 3800 μg·mg_Ru^–1·h^–1, compared to 590 μg·mg_Ru^–1·h^–1 for 40 wt % Ru/C at 2 V. ... Read more

We demonstrate a hybrid electrolyzer design for CO₂electrolysis to multicarbon products using a cation exchange membrane and different electrode separations. Reducing the thickness of the catholyte flow field from 5 to 2.4 mm significantly decreases the cell voltage while maintaining longer-term stability. ... Read more

Electrochemical carbon dioxide reduction (CO2R) is an attractive route to use renewable electricity to convert CO2 emissions to carbon-based chemicals. Continuous-flow electrolyzers with gas diffusion electrodes (GDEs) allow for the CO2R at high reaction rates. In addition to the electrolyzer configuration and operating conditions, the product selectivity strongly depends on the morphology of the electrocatalyst. This study demonstrates electrodeposition of copper (Cu) catalysts as a simple and efficient approach for preparing GDEs with good control over morphology. We study the influence of the activation process of the gas diffusion layer and the electrodeposition conditions on the morphology. Four Cu GDEs with different morphologies showed distinctly different current responses and product distributions. The partial current density for ethanol (jethanol) ranged from −18 mA cm–2 to −29 mA cm–2. Depending on the Cu GDE morphology, jethylene ranged between −25 mA cm–2 and −44 mA cm–2. Although the catalyst layers revealed surface restructuring after CO2 electrolysis, the morphologies remained distinctly different and retained the crystal structure of polycrystalline Cu. Electrodeposited Cu-GDEs maintained their selectivity for 6 h at a cell voltage of 4 V, representing a 5-fold improvement compared to sputtered Cu GDEs. Overall, this study demonstrates a facile approach for preparing GDEs with control over the catalyst morphology to tune CO2R to specific gaseous and liquid products. ... Read more