Limitations of Electrochemical Nitrogen Oxidation toward Nitrate

Activity Trend and Selectivity of Electrochemical Ammonia Synthesis in Reverse Artificial Nitrogen Cycle

Ammonia is important for modern agriculture and food production as it is a major source of fertilizer. Electrochemical ammonia synthesis (EAS) with sustainable energy generated electricity and decentralized reactors has been considered as environmentally friendly process. Several nitrogen sources have been considered and intensively studied in experiments and computations. Recently, it has been proposed and demonstrated that nitrogen oxides (NOx ) electroreduction for selective ammonia production is feasible. Fundamental insights on experimental observation are necessary for more rational design of catalysts and reactors in the future. In this concept, we review the theoretical and computational insights of electrochemical nitrogen oxides reduction, particularly, the activity trend over diverse transition metal catalysts and products selectivity at varying potentials. Finally, we address the opportunities and challenges in the reverse artificial nitrogen cycle, as well as fundamental issues in electrochemical reaction modelling.

Oxygen-deficient WO3-x spheres for electrochemical N2 oxidation to nitrate

Nitrate synthesis via the electrochemical nitrogen oxidation reaction (e-NOR) is widely recognized as a potential alternative to the energy-intensive Ostwald process. However, electrocatalysts with strong N2 adsorption and activation abilities remain largely undeveloped due to kinetic hindrances caused by the high bond energy of NN. Here we designed a hollow WO3 sphere with an optimal concentration of oxygen vacancies and studied its e-NOR performance. The optimally synthesized oxygen-deficient WO3 (WO3-x) achieved a high nitrate yield of 311.15 µmol h-1gcat.-1 and a Faraday efficiency of 2.00 %, which is probably due to the presence of a moderate amount of oxygen vacancies on the WO3-x surface and the hollow spherical structure, which further improves the accessibility of the inner active surface. Our work could potentially stimulate research into transition metal oxide-based materials for e-NOR applications.

Advanced (photo)electrocatalytic approaches to substitute the use of fossil fuels in chemical production

Electrification of the chemical industry for carbon-neutral production requires innovative (photo)electrocatalysis. This study highlights the contribution and discusses recent research projects in this area, which are relevant case examples to explore new directions but characterised by a little background research effort. It is organised into two main sections, where selected examples of innovative directions for electrocatalysis and photoelectrocatalysis are presented. The areas discussed include (i) new approaches to green energy or H2 vectors, (ii) the production of fertilisers directly from the air, (iii) the decoupling of the anodic and cathodic reactions in electrocatalytic or photoelectrocatalytic devices, (iv) the possibilities given by tandem/paired reactions in electrocatalytic devices, including the possibility to form the same product on both cathodic and anodic sides to "double" the efficiency, and (v) exploiting electrocatalytic cells to produce green H2 from biomass. The examples offer hits to expand current areas in electrocatalysis to accelerate the transformation to fossil-free chemical production.