Recent Progress in 2D Catalysts for Photocatalytic and Electrocatalytic Artificial Nitrogen Reduction to Ammonia

Abstract

produce H 2. Therefore, the prospect of NH 3 chemistry is very attractive. However, because nitrogen (N 2) molecules are very stable and difficult to activate, the current NH 3 synthesis process mainly uses the Haber-Bosch reaction which can be realized under high temperature and pressure (300-500 °C, 100-200 atmosphere). [2] This NH 3 synthesis method is energyconsuming and environment-unfriendly, which consumes 3-5% of the global methane and 1-2% of the global energy, and produces 1.6% of the carbon dioxide (CO 2) emissions. [2a] Therefore, developing the green and sustainable NH 3 synthesis approach is very urgent. Catalyst is the key to NH 3 synthesis, and many researchers have been committed to developing catalysts that can operate under normal temperature and pressure. Many plants can convert N 2 in the air into NH 3 fertilizer through nitrogenase, providing nutrients for their own growth. [3] Further study and analysis showed that the nitrogenase mainly contained ferritin and molybdenum-iron protein, which played an important role in the reduction of N 2 molecules. However, due to the slow reaction of nitrogenase in N 2 fixation process, [4] the research is directed to developing other more efficient approaches. For example, photo catalytic and electrocatalytic N 2 reduction reaction (N 2 RR) at room temperature and pressure are more effective methods to convert N 2 into NH 3. [5] Its raw material is H 2 O and N 2 , the overall reaction is 3H 2 O + N 2 → 2NH 3 + 3/2O 2. Only endless solar energy or clean electricity is needed to continuously convert N 2 to NH 3. It is of great significance in energy and environmental protection to convert the clean energy of light and electricity into chemical energy and realize the efficient utilization and transformation of renewable energy. Therefore, it has aroused the widespread interest of scientific researchers. The process of photocatalytic N 2 RR can be divided into two steps. First, photogenerated electrons are excited to the conduction band, leaving photogenerated holes in the valence band. Then some electrons and holes recombine, while the other part migrates to the photocatalysts' surface to participate in the redox process. The H 2 O can be oxidized into O 2 by photogenerated holes, while the N 2 can combine with photogenerated electrons and protons to form NH 3 through a series of reduction steps. The electrocatalytic N 2 RR reactor consists of an electrolytic Photocatalytic and electrocatalytic N 2 reduction reactions (N 2 RR) for NH 3 synthesis from abundant N 2 , H 2 O, solar energy, and renewable electricity is very attractive. 2D catalysts, including photocatalysts (TiO 2 , Bismuthbased materials, layered double hydroxides (LDHs), carbon nitride, Fe@ Graphene, MoS 2 et al.) and electrocatalysts (metal, graphene, carbon, boron nitride (BN), boron carbide (B 4 C), black phosphorus (BP), boron, transitionmetal oxide/sulfide/nitride/phosphide), have emerged as promising candidates for N 2 RR due to their unique physical, chemical and electronic properties. ...

2D materials: increscent quantum flatland with immense potential for applications

“…Catalytic synthesis of NH 3 can be conducted under ambient conditions. Hence, photocatalytic and electrocatalytic N 2 reduction reactions are more effective methods [ 168 ].…”

A minireview on catalysts for photocatalytic N2 fixation to synthesize ammonia

“…[11][12][13][14][15][16][17][18] It is a safe and green approach and has great potential to solve the problems encountered in the industrialized Haber-Bosch process, provided that efficient photocatalysts are adopted. [19][20][21][22][23][24][25][26][27][28][29][30][31] In photocatalytic N 2 xation reaction, the cleavage of the N^N bond is the rate determining step. That is, effective catalysts for PNF should be able to accelerate the N^N bond cleavage process.…”

Synthesis of two-dimensional ultrathin photocatalytic materials towards a more sustainable environment

“…2D chalcogenide materials composed of metal sulfides, metal selenides and metal tellurides are typical inorganic photocatalysts, and a series of reviews have been published on the preparation of each subclass in recent years. 14–18 In addition, the famous molybdenum sulfides and molybdenum selenides are widely used in photocatalysis as cocatalysts, due to their narrow bandgap (1–2 eV). 19–21 Hence, in this review, the emerging 2D bismuth oxyhalides are selected as the representative of 2D inorganic photocatalysts with non-toxicity, high stability and tuneable band structure.…”