Recent Progress on Electrocatalyst and Photocatalyst Design for Nitrogen Reduction

Abstract

Ammonia is one of the most important chemicals due to its enormous applications in fertilizer production and as an energy carrier. The production of ammonia mainly relies on the traditional Haber–Bosch process under high temperature and pressure, leading to massive energy consumption and notable environmental issues. Recently, electrocatalytic and photocatalytic nitrogen (N2) fixation have emerged for achieving green production of ammonia owing to their features of environmental friendliness and cost‐effectiveness. However, ammonia production through electrocatalysis and photocatalysis is still far away from practical applications. To facilitate the practical applications, a thorough understanding of nitrogen fixation is highly desired for the future design of high‐efficiency catalysts. Here, the fundamental investigations on electrocatalytic and photocatalytic N2 reduction are summarized. Based on the fundamental understanding, the current approaches and design strategies for heterogeneous catalysts toward electrocatalytic and photocatalytic N2 reduction are then presented. Finally, the remaining challenges and future opportunities in this field are outlined, leveraging the existing understanding on structure–property relationships. It is anticipated that this review sheds some light on the development of advanced catalytic systems for ammonia production through N2 fixation.

Low‐Coordinate Step Atoms via Plasma‐Assisted Calcinations to Enhance Electrochemical Reduction of Nitrogen to Ammonia

“…The concentration of a possible byproduct N 2 H 4 was examined by the method of Watt and Chrisp. [ 2,47,48 ] Similarly, the standard curve was constructed by measuring a series of absorbances for the reference solutions with different N 2 H 4 concentrations (0, 0.2, 0.4, 0.6, 0.8, 1.0, and 2.0 µg mL −1 ) in 0.05 m H 2 SO 4 solution (Figure S6, Supporting Information). The color reagent was prepared by mixing 5.99 g C 9 H 11 NO, 30 mL HCl, and 300 mL ethanol.…”

Formation of BNC Coordination to Stabilize the Exposed Active Nitrogen Atoms in g‐C3N4 for Dramatically Enhanced Photocatalytic Ammonia Synthesis Performance

“…[1,2] More seriously, the industrial Haber-Bosch process consumes nearly 2% of the world annual energy supply and produces more than 2 tons of CO 2 per year. [3,4] Due to wide applications of NH 3 product in chemical synthesis industry, the development of energy-efficient and ambient NH 3 synthesis technology through fixation of atmospheric N 2 is highly desirable, but great challenging. [5][6][7] Currently, photo(electro)catalytic N 2 reduction has been regarded as a promising means for sustainable NH 3 synthesis at ambient conditions.…”

Atomic Modulation, Structural Design, and Systematic Optimization for Efficient Electrochemical Nitrogen Reduction

“…The overall electrocatalytic system serves as the media for nitrogen dissolution and transport to the electrocatalyst surfaces, as a proton source for dinitrogen hydrogenation, and a key factor for modulation of electrocatalytic activity. Therefore, electrocatalysts in conjunction with a matching electrocatalytic system may markedly lower the activation energy of the NN triple bond, which is the most critical step in electrochemical ammonia synthesis …”

“…Further research is necessary to fully address the efficiency bottlenecks in electrocatalytic nitrogen reduction because of insufficient design guiding principles. On the other hand, mechanistic understanding of nitrogen reduction processes continues to be delineated by studying molecular and enzyme catalyzes, affording some activity‐relevant structural information for electrocatalyst design. It is worth noting that the dinitrogen electroreduction processes on heterogeneous electrocatalysts are different to molecular and enzymatic catalyzes, especially in proton‐coupled electron transfer (PCET) processes and electrocatalytic environments.…”