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.

Electrochemical CO₂ reduction to CO offers a sustainable route for converting CO₂ into value-added chemicals and fuels. However, CO₂ streams derived from industrial sources often contain SO₂ impurities that severely poison conventional metal-based catalysts. Here, we report a nitrogen-doped carbon catalyst that exhibits pronounced tolerance and stability for CO₂-to-CO conversion in the presence of SO₂ (100–10,000 ppm). The catalyst maintains over 90% Faradaic efficiency toward CO during 8 h of electrolysis at −1.0 V vs RHE with 100 ppm of SO₂, whereas Ag foil electrodes undergo rapid deactivation. Density functional theory calculations combined with surface analyses indicate that weak SO₂ adsorption and the absence of stable sulfur accumulation on nitrogen-doped carbon strengthen its resistance to impurity-induced deactivation, in contrast to Ag catalysts that form Ag₂S. Gas-fed tests in a membrane electrode assembly (MEA) electrolyzer further confirm that nitrogen-doped carbon sustains high CO selectivity at elevated current densities, while Ag nanoparticles suffer irreversible sulfur poisoning. These results demonstrate that nitrogen-doped carbon is intrinsically resistant to SO₂-induced deactivation and highlight its potential as a robust catalyst for CO₂ electroreduction under impurity-containing conditions.

Nitrogen-doped (N-doped) carbon catalysts have been widely studied for electrochemical CO₂ reduction to CO. However, the correlation between the physicochemical properties of N-doped carbon catalysts and their electrocatalytic performance for the CO₂RR is still unclear. Herein, a series of N-doped biochar catalysts with different physicochemical properties were synthesized by tuning the carbonization temperature and N-doping level and used for the CO₂RR to analyze the structure-performance relationship. The prepared catalysts exhibited massive differences in maximum faradaic efficiency to CO from 26.8 to 94.9% at around −0.8 to −0.9 V vs RHE. In addition, we find that simply increasing the specific surface area and N-doping level of the catalysts does not effectively improve the catalytic performance for the CO₂RR. A multivariate correlation analysis reveals a negative correlation between the N-doping content and the electrochemical performance. The porous structural properties exhibit a positive correlation to the FE_CO but almost no correlation to j_CO. Interestingly, improving the degree of graphitization, surface hydrophobicity, the abundance of defects, and optimizing the porosity of the N-doped biochar catalyst can efficiently enhance the catalytic performance for the CO₂RR. We conclude that comprehensively analyzing the synergistic effect of various properties of N-doped biochar is critical to reveal structure-activity relationships.

N-doped carbon materials can be efficient and cost-effective catalysts for the electrochemical CO₂ reduction reaction (CO₂RR). Activators are often used in the synthesis process to increase the specific surface area and porosity of these carbon materials. However, owing to the diversity of activators and the differences in physicochemical properties that these activators induce, the influence of activators used for the synthesis of N-doped carbon catalysts on their electrochemical performance is unclear. In this study, a series of bagasse-derived N-doped carbon catalysts is prepared with the assistance of different activators to understand the correlation between activators, physicochemical properties, and electrocatalytic performance for the CO₂RR. The properties of N-doped carbon catalysts, such as N-doping content, microstructure, and degree of graphitization, are found to be highly dependent on the type of activator applied in the synthesis procedure. Moreover, the overall CO₂RR performance of the synthesized electrocatalysts is not determined only by the N-doping level and the configuration of the N-dopant, but rather by the overall surface chemistry, where the porosity and the degree of graphitization are jointly responsible for significant differences in CO₂RR performance.

Preparing supported nanoparticles with a well-defined structure, uniform particle size, and composition using conventional catalyst synthesis methods, such as impregnation, precipitation, and deposition-precipitation is challenging. Furthermore, these liquid phase methods require significant solvent consumption, which has sustainable issues and requires complex purification processes, usually leaving impurities on the catalyst, affecting its selectivity and activity. In this work, we employed atomic layer deposition (ALD, a vapor phase synthesis method) to synthesize electrocatalysts with well-controlled core-shell and alloy structures for CO₂ reduction to formic acid. With this approach, the structural control of the catalysts is down to the atomic scale, and the effect of core-shell and alloy structure on Pt−Pd bimetallic catalysts has been investigated. It is shown that the Pt−Pd alloy catalyst displays a 46 % faradaic efficiency toward formic acid, outperforming Pt@Pd and Pd@Pt core-shell structures that show faradaic efficiencies of 22 % and 11 %, respectively. Moreover, both core-shell bimetallic catalysts (Pd@Pt and Pt@Pd) are not stable under electroreduction conditions. These catalysts restructure to more thermodynamically stable structures, such as segregated clusters or alloy particles, during the electrochemical reduction reaction, altering the catalytic selectivity.