Photo(electro)catalytic nitrogen fixation is considered as a competing alternative for the Haber–Bosch (HB) process due to the direct production of ammonia (NH3) from nitrogen and water with zero carbon dioxide emission, which has made it a very hot research topic in recent years. Particularly, photo‐driven nitrogen reduction has been attracted to a specific focus in the scientific community since it can be powered by limitless solar energy at ambient conditions. However, unsolved challenges have remained to date such as, electron–hole separation, low quantum efficiency, weak visible light harvesting, catalytic selectivity, N2 adsorption, and activation. In this Review, the recent achievements and related approaches toward nitrogen fixation are presented. In addition, the discussions on mechanistic photofixation of nitrogen, catalytic engineering design, and the outlook for enhancing the photocatalytic performance of ammonia photosynthesis are also devoted. Finally, the emerging trend of advanced photo(electro)catalysts for nitrogen fixation is proposed.

Nickel deposited S-doped carbon nitride (Ni–S:g-C3N4/Ni-SCN) nanosheets have been synthesized using calcination followed by a sulfidation process. X-ray photoelectron spectra revealed that the doped S atoms are successfully introduced into the 301 lattices of the host g-C3N4. XPS spectra indicated that the deposited Ni species are chemically bonded onto the host SCN nanosheets through sulfur bonds. The sunlight-driven photocatalytic hydrogen production efficiency of the synthesized Ni-SCN nanosheets is found to be 3628 μmol g–1 h–1, which is around 1.5 folds higher than that of Pt-SCN that synthesized in the present study. The observed efficiency is attributed to the chemical bonding of Ni through S that largely favored the photocatalytic process in terms of charge-separation as well as self-catalytic reactions. The apparent quantum efficiency of the photocatalyst at 420 nm is estimated to be 17.2%, which is relatively one of the higher values reported in the literature. The photocatalytic recyclability results showed consistent hydrogen evolution efficiency over 4 cycles (8 h) that revealed the excellent stability of the photocatalyst. This work has demonstrated that the chemical bonding of cocatalyst onto the host photocatalyst is relatively an effective strategy as compared to the conventional deposition of cocatalyst by means of electrostatic or van der Waals forces.

The photoassisted catalytic reaction, conventionally known as photocatalysis, is expanding into the field of energy and environmental applications. It is widely known that the discovery of TiO2‐assisted photochemical reactions has led to several unique applications, such as degradation of pollutants in water and air, hydrogen production through water splitting, fuel conversion, cancer treatment, antibacterial activity, self‐cleaning glasses, and concrete. These multifaceted applications of this phenomenon can be enriched and expanded further if this process is equipped with more tools and functions. The term “photoassisted” catalytic reactions clearly emphasizes that photons are required to activate the catalyst; this can be transcended even into the dark if electrons are stored in the material for the later use to continue the catalytic reactions in the absence of light. This can be achieved by equipping the photocatalyst with an electron‐storage material to overcome current limitations in photoassisted catalytic reactions. In this context, this article sheds lights on the materials and mechanisms of photocatalytic reactions under light and dark conditions. The manifestation of such systems could be an unparalleled technology in the near future that could influence all spheres of the catalytic sciences.

Photoelectrochemical (PEC) nitrogen fixation has opened up new possibilities for the production of ammonia from water and air under mild conditions, but this process is confronted by the inherent challenges associated with theoretical and experimental works, limiting the efficiency of the nitrogen reduction reaction. Herein, we report for the first time a novel and efficient photoelectrocatalytic system, which has been prepared by assembling plasmonic Au nanoparticles with Fedoped W 18 O 49 nanorods (denoted as WOF-Au). (i) The introduction of exotic Fe atoms into nonstoichiometric W 18 O 49 can eliminate bulk defects of the W 18 O 49 host, which resulted in narrowing bandgap energy and facilitating electron−hole separation and transportation. (ii) Meanwhile, Au nanoparticles combined with a semiconductor induce the localized surface plasmon resonance and generate energetic (hot) electrons, increasing electron density on W 18 O 49 nanorods. Consequently, this plasmonic WOF-Au system shows an NH 3 production yield of 9.82 μg h −1 cm −2 at −0.65 V versus Ag/AgCl, which is ∼2.5-folds higher than that of the WOF (without Au loading), as well as very high stability, and no NH 3 formation was found for the bare W 18 O 49 (WO). This high activity can be associated with the synergistic effects between the Fe dopant and plasmonic Au NPs on the host semiconductor W 18 O 49 . This work can bring some insights into the target-directed design of efficient plasmonic hybrid systems for N 2 fixation and artificial photocatalysis.

We have demonstrated the crucial role of nitrogen vacancies toward the enhancement of the plasmonic properties of Au/g-C 3 N 4 nanocomposites, which were prepared via the alkali-assisted synthesis and postcalcination pathway, for the effective production of hydrogen through a photocatalytic process under simulated solar light. The resulting material consisted of the nitrogen defective crumpled nanolayers of g-C 3 N 4 with strongly integrated Au plasmonic nanoparticles. It is realized from the studies that the nitrogen vacancies facilitate a stronger interaction with Au NPs and create the coexistence of the states of Au and Au (δ−) , which is eventually found to be the origin of the observed enhanced plasmonic properties of the nanocomposite. Such features have not been observed in any other conventional methods for the preparation of Au/g-C 3 N 4 , where it significantly improved (i) the light utilization abilities of the materials and (ii) electron−hole generation and separation, which collectively led to the boosting of the photocatalytic performance toward hydrogen production under simulated solar light.