Emerging p-Block-Element-Based Electrocatalysts for Sustainable Nitrogen Conversion

Abstract

Artificial nitrogen conversion reactions, such as the production of ammonia via dinitrogen or nitrate reduction and the synthesis of organonitrogen compounds via C−N coupling, play a pivotal role in the modern life. As alternatives to the traditional industrial processes that are energy-and carbon-emission-intensive, electrocatalytic nitrogen conversion reactions under mild conditions have attracted significant research interests. However, the electrosynthesis process still suffers from low product yield and Faradaic efficiency, which highlight the importance of developing efficient catalysts. In contrast to the transition-metal-based catalysts that have been widely studied, the p-block-element-based catalysts have recently shown promising performance because of their intriguing physiochemical properties and intrinsically poor hydrogen adsorption ability. In this Perspective, we summarize the latest breakthroughs in the development of p-block-elementbased electrocatalysts toward nitrogen conversion applications, including ammonia electrosynthesis from N 2 reduction and nitrate reduction and urea electrosynthesis using nitrogen-containing feedstocks and carbon dioxide. The catalyst design strategies and the underlying reaction mechanisms are discussed. Finally, major challenges and opportunities in future research directions are also proposed.

Review on Electrocatalytic Coreduction of Carbon Dioxide and Nitrogenous Species for Urea Synthesis

“…Moreover, the *N=N* is also easy to be formed by the adsorption and activation of N 2 on the catalyst surface in a N 2 -saturated electrolyte . However, the catalytic performance of urea electrosynthesis from CO 2 and N 2 is not ideal, and the urea yield is usually below 10 mmol h –1 g –1 . ,,, This may be due to that the N-containing reactive intermediate that forms the first C–N bond is the product after the breakage of the N–N triple bond.…”

“…The electrocatalytic process occurs at the liquid–solid/gas–solid interface, and the adsorption and desorption behaviors of reactive species on the surface of heterogeneous catalysts are strongly influenced by the surface atom composition and electronic structure of the catalysts. Moreover, electrochemical urea synthesis is an integrated multistep proton-coupling electron transfer process and C–N coupling steps. , Because the reduction efficiency of active sites from the same metal on two different reactive species (carbon- and nitrogen-containing species) cannot reach the optimal simultaneously, the design of dual-site catalysts may be a promising approach for enhancing the performance via the synergistic effect between different metal catalytic sites . Therefore, the construction of surface vacancy engineering, the construction of transition metal alloy nanostructures or heterostructures, heteroatom doping, diatomic or multiatomic catalysts, and so on are promising avenues to optimize electrochemical urea synthesis performance.…”

“…80 However, the catalytic performance of urea electrosynthesis from CO 2 and N 2 is not ideal, and the urea yield is usually below 10 mmol h −1 g −1 . 13,26,32,81 This may be due to that the N-containing reactive intermediate that forms the first C−N bond is the product after the breakage of the N− N triple bond. Summary.…”

“…To find nitrogen-containing alternatives, in 2022, Zhang and colleagues reported that using NO contaminants as nitrogen sources and H 2 O as the hydrogen source electrochemically converts CO 2 and NO into urea on a ZnO nanosheet catalyst under ambient conditions . Although there have been a notable number of studies in the field of electrochemical urea synthesis based on the electrocatalytic coreduction of CO 2 and nitrogenous species, existing catalysts are unable to adequately meet the requirements for large-scale commercial application owing to their low activity and selectivity for electrocatalytic urea synthesis. ,,,, Moreover, at present, few reviews have focused on the development process, catalyst design, and the reaction mechanism for electrocatalytic urea synthesis. Therefore, it is necessary to systematically conduct a review in terms of the development process for electrochemical urea synthesis, the composition and structure design of electrocatalysts, and the C–N coupling reaction mechanism.…”

P‐Block Metal‐Based Electrocatalysts for Nitrogen Reduction to Ammonia: A Minireview

“…Simultaneously, P‐block metal‐based partially occupied empty p‐orbitals lead to poor HER capacity. [ 32,33 ] Furthermore, P‐block metal‐based catalysts facilitate the electrochemical NRR, and the calculated density of states (DOS) reveals a large charge density near the Fermi level.…”