Photocatalytic vs. photosynthetic reduction of nitrogen into ammonia: The importance of the sacrificial reducing agent

Band structure engineering of bioinspired Fe doped SrMoO4 for enhanced photocatalytic nitrogen reduction performance

Artificial photosynthetic reduction of CO2 into valuable chemicals is one of the most promising approaches to solve the energy crisis and decreasing atmospheric CO2 emissions. However, the poor selectivity accompanied by the low activity of photocatalysts limits the development of photocatalytic CO2 reduction. Herein, inspired by the use of oxygen vacancy engineering to promote the adsorption and activation of CO2 molecules, we introduced oxygen vacancies in the representative barium titanate (BaTiO3) photocatalyst for photocatalytic CO2 reduction. We found that oxygen vacancies brought significant differences in the CO2 photoreduction activity and selectivity of BaTiO3. The intrinsic BaTiO3 showed a low photocatalytic activity with the dominant product of CO, whereas BaTiO3 with oxygen vacancies exhibited a tenfold improvement in photocatalytic activity, with a high selectivity of ~ 90% to CH4. We propose that the presence of oxygen vacancies promotes CO2 and H2O adsorption onto the BaTiO3 surface and also improves the separation and transfer of photogenerated carriers, thereby boosting the photocatalytic CO2 reduction to CH4. This work highlights the essential role of oxygen vacancies in tuning the selectivity of photocatalytic reduction of CO2 into valuable chemicals.

Redox regulation of photocatalytic nitrogen reduction reaction by gadolinium doping in two-dimensional bismuth molybdate nanosheets

Oxygen vacancy engineering of novel ultrathin Bi12O17Br2 nanosheets for boosting photocatalytic N2 reduction

Engineering of bionic Fe/Mo bimetallene for boosting the photocatalytic nitrogen reduction performance

Uniform NiPx nanospheres loaded onto defective HxWO3-y with three-dimensionally ordered macroporous structure for photocatalytic nitrogen reduction

During photocatalytic nitrogen fixation for ammonia synthesis, the photo-Dember effect causes direct transmission of photogenerated electrons from the illuminated surface to the bottom of photocatalyst, thus significantly reducing the number of charge carriers migrating on the surface and nitrogen fixation efficiency. Herein, a bismuth oxychloride material with largely exposed (101) crystal plane and rich oxygen vacancies (BOC(101)-OVs) is synthesized, exhibiting a high NH3 yield of 591.94µmolg-1h-1) after photocatalytic N2 reduction under simulated solar light irradiation. The designed (101)/(001) interface in BOC(101)-OVs generates a self-built electric field (Eself) on the material surface due to different atomic arrangements. Therefore, the newly developed material achieved >95% of photogenerated electrons changing the transfer path, i.e., from bulk phase transfer to surface lateral transfer path, thus escaping confinement by the photo-Dember effect. Meanwhile, after OVs construction, each adsorbed N2 molecule simultaneously bonds with three Bi atoms of material through N 2p-Bi 6p bonding, accelerating the filling of high-energy electrons into the π* orbital of N2, leading to a new nitrogen reduction path with combined alternating hydrogenation and terminal hydrogenation. This study greatly advances the beneficial effect of charge carrier migration through overcoming the photo-Dember effect for ammonia synthesis.

AcesExperimental and theoretical study on photocatalytic nitrogen reduction catalyzed by Fe doped MoO2

Interface engineered Co3O4-BiVO4 binary S-scheme heterostructure with improved topological features for enhanced photocatalytic hydrogen evolution and nitrogen reduction.

During photocatalytic nitrogen fixation for ammonia synthesis, the photo‐Dember effect causes direct transmission of photogenerated electrons from the illuminated surface to the bottom of photocatalyst, thus significantly reducing the number of charge carriers migrating on the surface and nitrogen fixation efficiency. Herein, a bismuth oxychloride material with largely exposed (101) crystal plane and rich oxygen vacancies (BOC (101) ‐OVs) is synthesized, exhibiting a high NH 3 yield of 591.94 µmol g −1 h −1 ) after photocatalytic N 2 reduction under simulated solar light irradiation. The designed (101)/(001) interface in BOC (101) ‐OVs generates a self‐built electric field ( E self ) on the material surface due to different atomic arrangements. Therefore, the newly developed material achieved >95% of photogenerated electrons changing the transfer path, i.e., from bulk phase transfer to surface lateral transfer path, thus escaping confinement by the photo‐Dember effect. Meanwhile, after OVs construction, each adsorbed N 2 molecule simultaneously bonds with three Bi atoms of material through N 2p–Bi 6p bonding, accelerating the filling of high‐energy electrons into the π* orbital of N 2 , leading to a new nitrogen reduction path with combined alternating hydrogenation and terminal hydrogenation. This study greatly advances the beneficial effect of charge carrier migration through overcoming the photo‐Dember effect for ammonia synthesis.

The electronic structure precision of single-atom catalysts (SACs) represents a decisive factor limiting advancements in photocatalytic nitrogen reduction (NRR) efficiency. This study addresses this issue by simultaneously introducing an axial fluoride ligand (F-) and engineering surface oxygen vacancies (Ov) around atomically dispersed Bi centers supported on W18O49 (denoted as FBWO). The axial fluoride ligand withdraws electron density away from the Bi site, increasing surface hydrophobicity and forming a surface dipole. This dipole lowers the conduction band while promoting side-on N2 chemisorption. Meanwhile, photo-induced Ov accumulate electrons around Bi site, forming a continuous F-Bi-Ov "electron pump" that reduces the activation energy for the first proton-electron transfer from 1.69eV (on pristine W18O49 with single Bi sites, BWO) to 0.87eV (on FBWO). These synergistic electronic and energetic modifications enable the material to achieve a visible-light NH3 production rate of 354.2 µmol g-1·h-1-8.4 times that of pristine W18O49 and twice that of BWO-surpassing all recently reported Bi- and W-based photocatalysts for N2 reduction. This work provides a unified design strategy that integrates ligand-field engineering with defect chemistry, facilitating the targeted development of SACs into high-performance photocatalysts for sustainable ammonia production.″.

Boosting the photocatalytic nitrogen reduction to ammonia through adsorption-plasmonic synergistic effects

Iron-titanium dioxide composite nanoparticles prepared with an energy effective method for efficient visible-light-driven photocatalytic nitrogen reduction to ammonia

The main obstacles to the photocatalytic reduction of nitrogen are the low separation efficiency of photogenerated charges and the few activation sites for nitrogen. It is highly desirable to explore new strategies for improving the nitrogen fixation performance of catalysts. Herein, the Bi metal active sites are constructed on the surface of BiOBr/BiOI heterojunction by in situ reaction, which promote the absorption, activation, and dissociation of nitrogen molecules. Moreover, the existence of Bi metal and BiOBr/BiOI heterojunction enhances the light absorption ability and facilitates the separation and transfer of photogenerated charges. The theoretical calculation also demonstrates that the BiOBr/BiOI/Bi composite has excellent electron structure and electron transfer efficiency. So, the ternary BiOBr/BiOI/Bi catalyst shows excellent performance of photocatalytic reduction of nitrogen to ammonia. The nitrogen reduction rate is 221.9 μmol g−1 h−1, which is 7.6 and 5 times higher than that of pure BiOBr and BiOBr/BiOI. The mechanism of photocatalytic nitrogen fixation of the BiOBr/BiOI/Bi is proposed based on the experimental and theoretical results. This study provides a novel method for improving the photocatalytic nitrogen reduction performance of catalysts.

Aiming to improve the photocatalytic activity in N2 fixation to produce ammonia, herein, we proposed a photochemical strategy to fabricate defects, and further deposition of Ru single atoms onto UiO-66 (Zr) framework. Electron-metal-support interactions (EMSI) were built between Ru single atoms and the support via a covalently bonding. EMSI were capable of accelerating charge transfer between Ru SAs and UiO-66, which was favorable for highly-efficiently photocatalytic activity. The photocatalytic production rate of ammonia improved from 4.57 μmol g-1 h-1 to 16.28 μmol g-1 h-1 with the fabrication of defects onto UiO-66, and further to 53.28 μmol g-1 h-1 with Ru-single atoms loading. From the DFT results, it was found that d-orbital electrons of Ru were donated to N2 π✶-antibonding orbital, facilitating the activation of the N≡N triple bond. A distal reaction pathway was probably occurred for the photocatalytic N2 reduction to ammonia on Ru1 /d-UiO-66 (single Ru sites decorated onto the nodes of defective UiO-66), and the first step of hydrogenation of N2 was the reaction determination step. This work shed a light on improving the photocatalytic activity via feasibly anchoring single atoms on MOF, and provided more evidences to understand the reaction mechanism in photocatalytic reduction of N2 .