Heteropoly Blue/Protonation-Defective Graphitic Carbon Nitride Heterojunction for the Photo-Driven Nitrogen Reduction Reaction

Abstract

The establishment of a heterojunction is a crucial strategy to design highly effective nonnoble metal nanocatalysts for the photocatalytic nitrogen reduction reaction (PNRR). Heteropoly blues (r-POMs) can act as electron-transfer mediators in PNRR, but its agglomeration limits the further promotion of PNRR productivity. In this work, we construct a protonation-modified surface of N-vacancy g-C 3 N 4 (HV-C 3 N 4 ), achieving the high dispersion of r-POMs via the surface modification strategy. Enlightened by the synergy effect of the nitrogenase, r-POMs were anchored onto HV-C 3 N 4 nanosheets through an electrostatic self-assembly method for preparing r-POMs-based protonation-defective graphitic carbonitride (HV-C 3 N 4 /r-POMs). As an electron donor, r-PW 12 can match with the energy level of HV-C 3 N 4 to build a heterojunction. The electron redistribution of the heterojunction facilitates the optimization of the electronic structure for enhancing the performance of PNRR. HV-C 3 N 4 /r-PW 12 exhibits the best PNRR efficiency of 171.4 μmol L −1 h −1 , which is boosted by 94.39% (HV-C 3 N 4 ) and 86.98% (r-PW 12 ). The isotope 15 NH 4 + experiment proves that ammonia is derived from N 2 , not carbon nitride. This study opens up a crucial view to achieve the high dispersion of r-POMs nanoparticles and develop high-efficiency nonnoble metal photocatalysts for the PNRR.

Encapsulation of Polymetallic Oxygen Clusters in a Mesoporous/Microporous Thorium-Based Porphyrin Metal–Organic Framework for Enhanced Photocatalytic CO2 Reduction

“…On the basis of this and previous related results, a possible mechanism pathway for photocatalytic CO 2 RR is proposed for POMs@ IHEP-20 (Figure c). ,, First, under visible light, the photosensitive porphyrin ligands generate photogenerated carriers to the oxide TEOA to the aldehyde TEOA + (Figure S10). , Second, the reduced porphyrin MOF would transfer the photogenerated electrons to the POMs, thereby reducing the POMs to a reduced state (namely, as POMs-red). − Finally, the photogenerated electrons accumulate in POMs-red and undergo a two- or eight-electron process to realize the photocatalytic reduction of CO 2 to CO or CH 4 . − …”

Designing “Core–Shell” Insoluble‐SiW11Fe@δ‐Bi2O3 Z‐Scheme Heterojunction for Photo‐Driven Nitrogen Reduction Reaction and Evaluating the Impact of Oxygen toward Nitrogen Reduction

“…The AQE was calculated according to Equation (). [ 39 ] where, N e , N p , and N NH3 represent the number of reacted electrons, incident photons, and generated ammonia, respectively. Then, n NH3 is the generated ammonia in molar.…”

“…[ 34,35 ] Then, semiconductor‐like polyoxometalates (POMs) are widely employed to construct heterojunction, owing to their merits of reversible redox featured with multi‐electron transfer and extended light absorption adjusted by transition metal substitutions. [ 36–38 ] In photo‐driven process, certain POMs derived catalysts have been developed for nitrogen fixation in water using nitrogen or air as feedstocks, such as HV‐C 3 N 4 / r ‐PW 12 , [ 39 ] Ag/PW 12 /Zr‐ m TiO 2 , [ 40 ] SiW 9 Co 3 /PDA/BWO, [ 41 ] and SiW 12 /K‐C 3 N 4 . [ 42 ] From a practical viewpoint, air would be better feedstock in comparison with pure nitrogen, yet NH 3 /NH 4 + production reduces under air atmosphere.…”

Recent Advances in MOF‐Based Materials for Photocatalytic Nitrogen Fixation

“…introduced polyoxometalates (POMs) into the porous structure of MOF through in situ synthesis and prepared a series of ZIF‐67@POMs materials (Figure 11). [112] POMs have been considered as a promising optoelectronic material because of its unique semiconductor characteristics [113] . Unfortunately, POMs is an unstable catalyst that can be dissolved in water and lost from the carrier.…”