Dual Active Sites Boosting Photocatalytic Nitrogen Fixation over Upconversion Mineral Nanocomposites under the Full Spectrum

Abstract

Photocatalytic nitrogen fixation has been considered as one of the most potential alternatives for the synthesis of ammonia; however, how to make full use of solar energy and how to cleave the strong NN bond remain great challenges. Herein, the attapulgite (ATP) mineral was modified with iron followed by the immobilization of doped CeF 3 nanoparticles to form a CeF 3 :Yb 3+ , Er 3+ /Fe-ATP heterostructure, which was utilized as a photocatalyst for nitrogen fixation. Results showed that doping of the activator Yb 3+ and the sensitizer Er 3+ generated fluorine vacancies (F v ) in the CeF 3 matrix, which formed dual active sites with Fe ions in ATP, benefiting the adsorption and activation of N 2 molecules. In addition, Fe-reconstructed ATP had a narrow band gap responsive in the visible region, while CeF 3 -doped Yb 3+ and Er 3+ facilitated transforming near-infrared light (NIR) into ultraviolet (UV) and visible light, both of which contributed to extending the harvest range in the full spectrum. The influence of the Er 3+ doping ratio and loading amount of fluoride on the generation of ammonia was explored. Notably, the separation of photogenerated charge carriers and the redox potentials was enhanced due to the rational indirect Z-scheme heterostructure mediated by F v . Under solar light irradiation, the NH 4 + production rate achieved the highest value of 253.6 μmol•h −1 •g −1 when the Er doping amount was optimized to be 3 mol % and the loading of CeF 3 :Yb 3+ , Er 3+ was 20 wt %, and it even reached 40.3 μmol•h −1 •g −1 under NIR irradiation. The current study may offer a sustainable strategy to use full solar energy and natural minerals for efficient ammonia synthesis.

Advanced Strategies for Improving the Photocatalytic Nitrogen Fixation Performance: A Short Review

“…For instance, Ding et al constructed Z-scheme heterojunction MOF-74(Zn)/g-C 3 N 4 by dispersing MOF-74 on nitrogendeficient g-C 3 N 4 films by a simple sol−gel method to improve the photocatalytic nitrogen fixation performance significantly. 72 Li et al successfully prepared a self-recovery and recyclable polyoxometalates (POMs)/MOFs (POMs/ZIF-67) composite photocatalytic nitrogen fixation system (Figure 8c). The 8), the photocatalytic nitrogen fixation synthesis of NH 3 under visible light at room temperature and pressure was achieved.…”

“…In addition, Fv forms a double active site with Fe ions in adenosine triphosphate (ATP), which facilitates the adsorption and activation of N 2 . Other representative examples include MOF-74­(Zn)/g-C 3 N 4 , (BiO) 2 CO 3 –BiOCl, CoFe 2 O 4 /g-C 3 N 4 , etc.…”

Structural design and control of photocatalytic nitrogen-fixing catalysts

“…Zuo et al 90 constructed a CeF 3 :Yb 3+ , Er 3+ /Fe-ATP nanocomposite that can broaden the light response range and increase the utilization rate of light, and also enhance the chemisorption and activation of N 2 and reduce photogenerated carriers binding. The main reason for these excellent properties of nanomaterials lies in the formation of a double-active site structure between fluorine vacancies (F v ) and Fe ions in ATP (Fig.…”

Construction of 2D Bismuth Silicate Heterojunctions from Natural Mineral toward Cost-Effective Photocatalytic Reduction of CO2

“…The clay sepiolite was modified by replacing the exchangeable cations with Zn or Cu ions. As a natural one-dimensional clay mineral rich in Mg and Al, palygorskite (Pal) has a large specific surface area and sufficient active site, which owns weak UV light responsiveness because the framework contains a small amount of iron. , In our previous work, the Pal clay treated with acid is replaced by Fe ion through the microwave-assisted hydrothermal method. The Fe-Pal retains the intrinsic structure of Pal and has a narrower band gap …”