Limitation of WO₃ in Zn-Co₃O₄ Nanopolyhedra by the Pyrolysis of H₃PW₁₂O₄₀@BMZIF: Synergistic Effect of Heterostructure and Oxygen Vacancies for Enhanced Nitrogen Fixation

Abstract

The photocatalytic nitrogen fixation process is a crucial step toward carbon neutrality and sustainable development. The combination of polyoxometalates and metal–organic frameworks is a viable method to achieve high-efficiency photocatalytic nitrogen fixation. In this work, we employed bimetallic ZIF (BMZIF) composed of Co2+ and Zn2+ encapsulated with H3PW12O40 (PW12) as the precursor to synthesize Zn-doped Co3O4 nanopolyhedra loaded with WO3 nanoparticles. The NH3 yield of WO3/Zn-Co3O4-2 with the best photocatalytic performance can reach 231.9 μmol g–1 h–1 under visible light, about 2.4 and 6.4 times those of pure Zn-Co3O4 and WO3, respectively. The rhombic dodecahedral geometry of BMZIF is still maintained in the synthesized WO3/Zn-Co3O4 nanopolyhedra, with the significant increase in the specific surface area after calcination showing better catalytic performance. At the same time, Zn doping and the formation of WO3 nanoparticles result in abundant oxygen vacancies in WO3/Zn-Co3O4 heterostructures. Oxygen vacancies can supply nitrogen with active sites for adsorption and activation and improve photocarriers’ capacity for separation, which can greatly increase the effectiveness of the photocatalytic synthesis of ammonia. This work can easily synthesize the heterostructure based on n-type WO3 nanoparticles and p-type Zn-doped Co3O4 nanopolyhedra, and the beneficial combination of POMs and metal–organic framework provides new thinking for the synthesis of efficient nitrogen-fixing photocatalysts.

Boosted Photocatalytic Performance for Antibiotics Removal with Ag/PW12/TiO2 Composite: Degradation Pathways and Toxicity Assessment

“…The P 2p peak of 10% Ag/PT was shifted towards the lower binding energy region in comparison with PT. In the PT material, the high-resolution XPS spectrum of the W 4f region (Figure 4d) showed two peaks at 35.58 eV and 37.63 eV for the W 4f 7/2 and W 4f 5/2 binding energies, respectively, and, in 10% Ag/PT, W 4f was shifted toward the lower binding energy with binding energies of 35.28 eV and 37.32 eV [41,42]. Figure 4e shows the presence of Ti 2p 3/2 and Ti 2p 1/2 characteristic peaks observed at 458.49 eV and 464.16 eV in PT, which are features of Ti 4+ in TiO 2 [43].…”

Hexanuclear nickel-added silicotungstates as high-efficiency electrocatalysts for nitrate reduction to ammonia

“…According to density functional theory calculations, POMs can serve as an electron source to provide electrons to the active site during the e-NRR [41,42]. The reduced POMs can also serve as an electronic library that provides electrons directly (or indirectly via catalysts) to substrates [43]. When the POMs take part in quick electron-transfer processes, they display great stability in their oxidized and reduced states [44].…”

Construction of Fe(III) Active Sites on Phenanthroline-Grafted g-C3N4: Reduced Work Function and Enhanced Intramolecular Charge Transfer for Efficient N2 Photofixation

“…Ammonia (NH 3 ) is an important chemical raw material and a very promising energy carrier. , The main source of NH 3 is atmospheric N 2 , but the N 2 molecule is very stable in the atmosphere, and the NN triple bond energy is so high (941 kJ/mol) that it cannot be used directly. , Today, the efficient production of ammonia in industry is still mainly based on the traditional Haber–Bosch process, but the harsh reaction conditions of this method, the need to consume large amounts of energy, and the emission of greenhouse gases put a great burden on energy and environmental protection. , Photocatalytic nitrogen fixation for NH 3 synthesis is a procedure that uses naturally abundant solar energy as the energy source and N 2 and H 2 O as the feedstock at room temperature and atmospheric pressure, with no carbon products emitted during the reaction process, and it is considered to be an ideal pathway for reducing N 2 to NH 3 to satisfy the carbon-neutral background …”