Fundamentals and Recent Progress of Photocatalytic Nitrogen‐Fixation Reaction over Semiconductors

Abstract

As a green energy carrier, a potential fuel and an essential chemical for the manufacturing of fertilizers, plastics, and explosives, ammonia (NH3) is currently produced by Haber−Bosch process. However, the process converting nitrogen (N2) into NH3 under strict conditions consumes substantial energy and releases enormous greenhouse gases. In the context of the global energy crisis and increasing greenhouse effect, it is urgent to explore mild, green, sustainable, and economic nitrogen‐fixation strategies. Very recently, photocatalytic nitrogen‐fixation reactions, including nitrogen reduction reaction (NRR) and nitrogen oxidation reaction (NOR), have aroused widespread attention due to its environmental friendliness and cost‐effectiveness. To achieve high photocatalytic performance and selectivity, it is necessary to design photocatalyst and its photoreaction system reasonably to optimize the light absorption, charge separation, mass transport, adsorption, and activation of N2 as well as proton/electron transfer. This review gives an overview of fundamentals, performance evaluation, and recent progress of the photocatalytic nitrogen‐fixation reactions. The photocatalysts and their design strategies are classified, and several suggestions are given for the analysis of the existing photocatalytic nitrogen‐fixation systems. Finally, a short perspective on the existing challenges and future opportunities are outlined for providing insights into the development of high‐efficiency photocatalytic systems for artificial N2 fixation.

Recent Advances in MOF‐Based Materials for Photocatalytic Nitrogen Fixation

“…In some cases, there are multiple reaction pathways for surface hydrogenation and reduction„ products in the form of N 2 H 4 , NO 3 − , etc. may also exist in the solution [81,82] . At present, commonly used methods for the detection of NH 4 + include spectrophotometry (such as Nessler's reagent method, indophenol blue method, salicylate method), ion chromatography, nuclear magnetic resonance (NMR) spectroscopy, and so on [83,84] .…”

Recent Progress of the Design and Engineering of Bismuth Oxyhalides for Photocatalytic Nitrogen Fixation

“…[79] Such BiOX-based catalysts exhibit apparent photocatalytic activity toward nitrogen fixation. [99][100][101][102][103][104][105][106][107][108][109][110][111][112][113][114] As depicted in Table 2, in a previous study, Li et al [46] prepared BiOBr nanosheets with abundant OVs on the exposed {001} surface and observed a photocatalytic nitrogen fixation rate of 104.2 μmol h À1 g À1 under visible light photoirradiation. In a later study, Wang et al [52] prepared Bi 5 O 7 Br nanotubes, and observed an improved photocatalytic nitrogen fixation rate of 1.38 mmol h À1 g À1 .…”

“…But, this is still far lower than actual industrial application requirements. [104] Nevertheless, such bismuth oxyhalides have been found to exhibit good stability and reusability (Table 2).…”

Rational design of photocatalysts for ammonia production from water and nitrogen gas

“…Another critical point to note in NH 3 production via photochemical N 2 reduction is the facile competitive hydrogen evolution reaction by water reduction. NH 3 production is kinetically much more complex than water reduction, although the thermodynamic requirements for those reactions are similar [23]. This indicates that photochemical H 2 production may be predominant, resulting in inactive NH 3 production.…”