Efficient Electrochemical Nitrate Reduction to Ammonia with Copper Supported Rhodium Cluster and Single‐Atom Catalysts

Sulphur-Boosted Active Hydrogen on Copper for Enhanced Electrocatalytic Nitrate-to-Ammonia Selectivity

Electrocatalytic nitrate reduction to ammonia is a promising approach in term of pollutant appreciation. Cu-based catalysts performs a leading-edge advantage for nitrate reduction due to its favorable adsorption with *NO3. However, the formation of active hydrogen (*H) on Cu surface is difficult and insufficient, leading to the significant generation of by-product NO2 -. Herein, sulphur doped Cu (Cu-S) is prepared via an electrochemical conversion strategy and used for nitrate electroreduction. The high Faradaic efficiency (FE) of ammonia (~98.3 %) and an extremely low FE of nitrite (~1.4 %) are achieved on Cu-S, obviously superior to its counterpart of Cu (FENH3: 70.4 %, FENO2 -: 18.8 %). Electrochemical in situ characterizations and theoretical calculations indicate that a small amount of S doping on Cu surface can promote the kinetics of H2O dissociation to active hydrogen. The optimized hydrogen affinity validly decreases the hydrogenation kinetic energy barrier of *NO2, leading to an enhanced NH3 selectivity.

Crystal Phase Engineering of Ultrathin Alloy Nanostructures for Highly Efficient Electroreduction of Nitrate to Ammonia

Electrocatalytic nitrate reduction reaction (NO3RR) toward ammonia synthesis is recognized as a sustainable strategy to balance the global nitrogen cycle. However, it still remains a great challenge to achieve highly efficient ammonia production due to the complex proton-coupled electron transfer process in NO3RR. Here, the controlled synthesis of RuMo alloy nanoflowers (NFs) with unconventional face-centered cubic (fcc) phase and hexagonal close-packed/fcc heterophase for highly efficient NO3RR is reported. Significantly, fcc RuMo NFs demonstrate high Faradaic efficiency of 95.2% and a large yield rate of 32.7 mg h-1 mgcat -1 toward ammonia production at 0 and -0.1 V (vs reversible hydrogen electrode), respectively. In situ characterizations and theoretical calculations have unraveled that fcc RuMo NFs possess the highest d-band center with superior electroactivity, which originates from the strong Ru─Mo interactions and the high intrinsic activity of the unconventional fcc phase. The optimal electronic structures of fcc RuMo NFs supply strong adsorption of key intermediates with suppression of the competitive hydrogen evolution, which further determines the remarkable NO3RR performance. The successful demonstration of high-performance zinc-nitrate batteries with fcc RuMo NFs suggests their substantial application potential in electrochemical energy supply systems.

Recent Advances in Electrocatalytic Hydrogenation Reactions on Copper-Based Catalysts

Hydrogenation reactions play a critical role in the synthesis of value-added products within the chemical industry. Electrocatalytic hydrogenation (ECH) using water as the hydrogen source has emerged as an alternative to conventional thermocatalytic processes for sustainable and decentralized chemical synthesis under mild conditions. Among the various ECH catalysts, copper-based (Cu-based) nanomaterials are promising candidates due to their earth-abundance, unique electronic structure, versatility, and high activity/selectivity. Herein, recent advances in the application of Cu-based catalysts in ECH reactions for the upgrading of valuable chemicals are systematically analyzed. The unique properties of Cu-based catalysts in ECH are initially introduced, followed by design strategies to enhance their activity and selectivity. Then, typical ECH reactions on Cu-based catalysts are presented in detail, including carbon dioxide reduction for multicarbon generation, alkyne-to-alkene conversion, selective aldehyde conversion, ammonia production from nitrogen-containing substances, and amine production from organic nitrogen compounds. In these catalysts, the role of catalyst composition and nanostructures toward different products is focused. The co-hydrogenation of two substrates (e.g., CO2 and NOx n, SO3 2-, etc.) via C─N, C─S, and C─C cross-coupling reactions are also highlighted. Finally, the critical issues and future perspectives of Cu-catalyzed ECH are proposed to accelerate the rational development of next-generation catalysts.

Thermally Enhanced Relay Electrocatalysis of Nitrate-to-Ammonia Reduction over Single-Atom-Alloy Oxides

The electrochemical nitrate reduction reaction (NO3RR) holds promise for converting nitrogenous pollutants to valuable ammonia products. However, conventional electrocatalysis faces challenges in effectively driving the complex eight-electron and nine-proton transfer process of the NO3RR while also competing with the hydrogen evolution reaction. In this study, we present the thermally enhanced electrocatalysis of nitrate-to-ammonia conversion over nickel-modified copper oxide single-atom alloy oxide nanowires. The catalyst demonstrates improved ammonia production performance with a Faradaic efficiency of approximately 80% and a yield rate of 9.7 mg h-1 cm-2 at +0.1 V versus a reversible hydrogen electrode at elevated cell temperatures. In addition, this thermally enhanced electrocatalysis system displays impressive stability, interference resistance, and favorable energy consumption and greenhouse gas emissions for the simulated industrial wastewater treatment. Complementary in situ analyses confirm that the significantly superior relay of active hydrogen species formed at Ni sites facilitates the thermal-field-coupled electrocatalysis of Cu surface-adsorbed *NOx hydrogenation. Theoretical calculations further support the thermodynamic and kinetic feasibility of the relay catalysis mechanism for the NO3RR over the Ni1Cu model catalyst. This study introduces a conceptual thermal-electrochemistry approach for the synergistic regulation of complex catalytic processes, highlighting the potential of multifield-coupled catalysis to advance sustainable-energy-powered chemical synthesis technologies.