Single molybdenum atom anchored on N-doped carbon as a promising electrocatalyst for nitrogen reduction into ammonia at ambient conditions

Ammonia (NH3) is one of the most important industrial chemicals owing to its wide applications in various fields. However, the synthesis of NH3 at ambient conditions remains a coveted goal for chemists. In this work, we study the potential of the newly synthesized single-atom catalysts, i.e., single metal atoms (Cu, Pd, Pt, and Mo) supported on N-doped carbon for N2 reduction reaction (NRR) by employing first-principles calculations. It is found that Mo1-N1C2 can catalyze NRR through the enzymatic mechanism with an ultralow overpotential of 0.24 V. Most importantly, the removal of the produced NH3 is rapid with a free-energy uphill of only 0.47 eV for the Mo1-N1C2 catalyst, which is much lower than that for ever-reported catalysts with low overpotentials and endows Mo1-N1C2 with excellent durability. The coordination effect on activity is further evaluated, showing that the experimentally realized active site, single Mo atom coordinated by one N atom and two C atoms (Mo-N1C2), possesses the highest catalytic performance. Our study offers new opportunities for advancing electrochemical conversion of N2 into NH3 at ambient conditions

A general two-step strategy-based high-throughput screening of single atom catalysts for nitrogen fixation

Electrocatalytic or photocatalytic N2 reduction holds great promise for green and sustainable NH3 production under ambient conditions, where an efficient catalyst plays a crucial role but remains a long‐standing challenge. Here, a high‐throughput screening of catalysts for N2 reduction among (nitrogen‐doped) graphene‐supported single atom catalysts is performed based on a general two‐step strategy. 10 promising candidates with excellent performance are extracted from 540 systems. Most strikingly, a single W atom embedded in graphene with three C atom coordination (W1C3) exhibits the best performance with an extremely low onset potential of 0.25 V. This study not only provides a series of promising catalysts for N2 fixation, but also paves a new way for the rational design of catalysts for N2 fixation under ambient conditions

Boosting urea electrooxidation on oxyanion-engineered nickel sites via inhibited water oxidation

Abstract Renewable energy-based electrocatalytic oxidation of organic nucleophiles (e.g.methanol, urea, and amine) are more thermodynamically favourable and, economically attractive to replace conventional pure water electrooxidation in electrolyser to produce hydrogen. However, it is challenging due to the competitive oxygen evolution reaction under a high current density (e.g., >300 mA cm−2), which reduces the anode electrocatalyst’s activity and stability. Herein, taking lower energy cost urea electrooxidation reaction as the model reaction, we developed oxyanion-engineered Nickel catalysts to inhibit competing oxygen evolution reaction during urea oxidation reaction, achieving an ultrahigh 323.4 mA cm−2 current density at 1.65 V with 99.3 ± 0.4% selectivity of N-products. In situ spectra studies reveal that such in situ generated oxyanions not only inhibit OH− adsorption and guarantee high coverage of urea reactant on active sites to avoid oxygen evolution reaction, but also accelerate urea’s C − N bond cleavage to form CNO − intermediates for facilitating urea oxidation reaction. Accordingly, a comprehensive mechanism for competitive adsorption behaviour between OH− and urea to boost urea electrooxidation and dynamic change of Ni active sites during urea oxidation reaction was proposed. This work presents a feasible route for high-efficiency urea electrooxidation reaction and even various electrooxidation reactions in practical applications

Single Molybdenum Atom Anchored on N‑Doped Carbon as a Promising Electrocatalyst for Nitrogen Reduction into Ammonia at Ambient Conditions

Ammonia (NH₃) is one of the most important industrial chemicals owing to its wide applications in various fields. However, the synthesis of NH₃ at ambient conditions remains a coveted goal for chemists. In this work, we study the potential of the newly synthesized single-atom catalysts, i.e., single metal atoms (Cu, Pd, Pt, and Mo) supported on N-doped carbon for N₂ reduction reaction (NRR) by employing first-principles calculations. It is found that Mo₁-N₁C₂ can catalyze NRR through the enzymatic mechanism with an ultralow overpotential of 0.24 V. Most importantly, the removal of the produced NH₃ is rapid with a free-energy uphill of only 0.47 eV for the Mo₁-N₁C₂ catalyst, which is much lower than that for ever-reported catalysts with low overpotentials and endows Mo₁-N₁C₂ with excellent durability. The coordination effect on activity is further evaluated, showing that the experimentally realized active site, single Mo atom coordinated by one N atom and two C atoms (Mo-N₁C₂), possesses the highest catalytic performance. Our study offers new opportunities for advancing electrochemical conversion of N₂ into NH₃ at ambient conditions

Bimetallic Nickel Cobalt Sulfide as Efficient Electrocatalyst for Zn–Air Battery and Water Splitting

Abstract The development of efficient earth-abundant electrocatalysts for oxygen reduction, oxygen evolution, and hydrogen evolution reactions (ORR, OER, and HER) is important for future energy conversion and energy storage devices, for which both rechargeable Zn–air batteries and water splitting have raised great expectations. Herein, we report a single-phase bimetallic nickel cobalt sulfide ((Ni,Co)S2) as an efficient electrocatalyst for both OER and ORR. Owing to the synergistic combination of Ni and Co, the (Ni,Co)S2 exhibits superior electrocatalytic performance for ORR, OER, and HER in an alkaline electrolyte, and the first principle calculation results indicate that the reaction of an adsorbed O atom with a H2O molecule to form a *OOH is the potential limiting step in the OER. Importantly, it could be utilized as an advanced air electrode material in Zn–air batteries, which shows an enhanced charge–discharge performance (charging voltage of 1.71 V and discharge voltage of 1.26 V at 2 mA cm−2), large specific capacity (842 mAh gZn−1 at 5 mA cm−2), and excellent cycling stability (480 h). Interestingly, the (Ni,Co)S2-based Zn–air battery can efficiently power an electrochemical water-splitting unit with (Ni,Co)S2 serving as both the electrodes. This reveals that the prepared (Ni,Co)S2 has promising applications in future energy conversion and energy storage devices