Topotactic Transformation of Solvated MgCr-LDH Nanosheets to Highly Efficient Porous MgO/MgCr₂O₄ Nanocomposite for Photocatalytic H₂ Evolution

Abstract

The hybrid structure of nanoparticles (NPs) with nanosheets has the advantage of both anisotropic properties of NPs and large specific surface areas of nanosheets, which is desirable for many technological applications. In this study, MgCrO spinel NPs decorated on highly porous MgO nanosheets forming MgO/MgCr O( x) nanocomposites were synthesized by a one pot coprecipitation method followed by a heat treatment process of the solvated wet gel of MgCr-LDH with polar solvent N, N-dimethylformamide (DMF) at 400 °C. This novel synthetic methodology generates materials consisting of porous metal oxides nanosheets adhered with spinel phase NPs due to the slow generation of gases such as HO, CO, and NH under moderate temperature during the heat treatment process. The synergistic effect of much wider band gap MgO nanosheets and narrow band gap MgCrO NPs added increased stability due to the stronger bonding coordination of MgCrO NPs with MgO nanosheets. The obtained MgO/MgCr O( x) nanocomposites possess large specific surface areas, highly porous structure, and excellent interface between MgCrO NPs and MgO nanosheets, which proved from N sorption isotherm, TEM, HR-TEM study. With metallic ratio of MgCr3:1, MgO/MgCrO(MgCr3:1) nanocomposites exhibit highest H evolution rate of 840 μmolg2h, which was 2 times higher than that of pure MgCrO(420 μmolg2h). The LSV measurement study of MgO/MgCrO (MgCr3:1) nanocomposite shows an enhancement of light current density of 0.22 μA/cm at potential bias of -1.1 V. The Mott-Schottky analysis suggested the band edge positions of the n-type constituents and formation of n-n type heterojunctions in MgO/MgCrO (MgCr3:1) nanocomposite, which facilitates the flow of charge carriers. The EIS and Bode phase plot of MgO/MgCrO (MgCr3:1) nanocomposite signifies the lower interfacial charge transfer resistance and higher lifetime of electrons (2.7 ms) for enhanced H production. Lastly, the enhanced photocatalytic H production activity and long-term stability of MgO/MgCrO(MgCr3:1) could be attributed to maximum specific surface area, porous structure, close intimacy contact angle between two cubic phases of MgCrO NPs and MgO nanosheets, abundant oxygen vacancies sites, reduced charge transfer resistance and suitable band edge potential to drive the thermodynamic energy for H production. This work highlighted an effective strategy for the synthesis of cost-effective 2D porous heterojunctions nanocomposite photocatalyst for promising applications in the field of clean H production utilizing abundant solar energy.

Deciphering Z-scheme Charge Transfer Dynamics in Heterostructure NiFe-LDH/N-rGO/g-C3N4 Nanocomposite for Photocatalytic Pollutant Removal and Water Splitting Reactions

“…What is more, N-doped graphene framework structure have greater advantages than 2D graphene framework and provide more efficient surface area via strong π– π interaction to directly couple transition metal atoms sites of exfoliated NiFe LDH nanosheets, leading to fast electron transfer kinetics and excellent stability 23–26 . Authors group have also reported various heterostructure based materials such as CeO 2 /MgAl-LDH, Co(OH) 2 /ZnCr LDH, Ag@Ag 3 PO 4 /g-C 3 N 4 /NiFe LDH, MgO/MgCr 2 O 4 derived from MgCr-LDH nanosheets for photocatalytic H 2 and O 2 production with Cr(VI) reduction and phenol degradation activities 27–30 . Among the above promising results of NiFe LDH based heterostructure materials 6–13 , there have been no reports on controlled coupling of NiFe LDH and g-C 3 N 4 with 2D N-doped graphene frameworks structure for photocatalytic removal of organic pollutant with productions of clean energy of H 2 and O 2 .…”

Full-Spectrum Photocatalytic Activity of ZnO/CuO/ZnFe2O4 Nanocomposite as a PhotoFenton-Like Catalyst

“…When photoactive metal oxides with suitable band gap structures are involved, MMOs derived from HLC calcination generally show superior photocatalytic performance compared to single metal oxides as semiconductor photocatalysts due to the extended absorption spectrum of the MMOs and reduced recombination rates for photogenerated carriers [7][8][9]. Deriving HLC-based photocatalysts by calcination has, therefore, attracted growing interest recently from the viewpoint of designing photocatalysts to either improve their photocatalytic performance [10][11][12][13] or extend their photocatalytic activity to the visible light region [14][15][16].…”

MAGNESIOCHROMITE (MgCr2O4) SYNTHESIS: EFFECT OF MECHANICAL AND MICROWAVE PRETREATMENT

“…It attracts the attention because of its unique physical and chemical properties and technological possibilities. This spinel is used in some refractories' composition [1,2], semiconductors [3], magnetic and electrical materials [4], sensors [5], catalysts [6][7][8], photocatalysts [9], pigments [10], etc. Active work on nanoceramics and nanocomposites with MgCr 2 O 4 participation [8,9,[11][12][13][14].…”