Nanostructured nickel phosphide-based catalysts having different sizes, phases, and morphology towards electrocatalytic, photocatalytic, and photoelectrocatalytic water splitting.

A mixed-valency bimetallic Ce/Zr MOF with Ce 3+ / Ce 4+ ions incorporated and an oxygen vacancy-rich singlecomponent photocatalyst have been designed through the onestep solvothermal route to harness photons from the visible-light spectrum for green energy (H 2 ) generation and ciprofloxacin (CIP) degradation. The one-pot-engineered bimetallic Ce/Zr MOF shows visible-light-active characteristics accompanied by a narrower band gap, along with enhanced exciton separation and superior ligand-to-metal charge transfer (LMCT), due to the presence of an interconvertible Ce 3+ /Ce 4+ ions pair in comparison to its pristine MOF counterpart. The Ce ion insertion led to increase in electron density around the Zr 4+ ion, along with generation of some oxygen vacancies (OV), which cumulatively led to the rise in the photo-reaction output. The synthesized UNH (Ce/Zr 1:1) MOF displayed a boosted photocatalytic H 2 production rate of 468.30 μmol h −1 (ACE = 3.51%), which is around fourfolds higher than that of pristine MOFs. Moreover, for CIP photodegradation, the UNH (Ce/Zr 1:1) shows an enhanced efficiency of 90.8% and follows pseudo-first-order kinetics with a rate constant of 0.0363. Typically, the active species involved in the photo-redox reaction of the CIP photodegradation follows the order hydroxyl radical (OH • ) < superoxide radical (O 2•− ), as confirmed by the TA and NBT tests. Consequently, the bimetallic Ce/Zr MOF can be readily employed as a robust photocatalyst with enhanced tendencies towards CIP degradation and H 2 evolution.

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The photocatalytic water and nitrogen reduction in the presence of solar light gives rise to an alternative route for sustainable green energy. This novel approach can resolve the difficulty of greenhouse gas emanation from fossil fuels and global warming and energy crisis. Making headway for developing more robust and efficient photocatalytic systems still remains an enormous challenge toward industrial usage on a large scale. To meet this challenge, herein we report hydrothermally prepared ZnO nanorods (NRs) coupled with nickel phosphide (Ni x P y ) via a lowtemperature phosphidation method. Ni x P y acts as a robust cocatalyst, which increases the visible light absorption efficacy and photocatalytic performance of ZnO NRs toward nitrogen reduction and hydrogen evolution. The nanorod morphology of the ZnO-Ni x P y hybrid is revealed by transmission electron microscopy (TEM) analysis while the formation of the Ni−P moiety and its interaction with ZnO NRs are verified by X-ray photoelectron spectroscopy (XPS) analysis. Besides, the excellent photogenerated charge separation and transfer efficiency are further confirmed using photoluminescence (PL), electrochemical impedance spectroscopy (EIS), and transient analysis, which are the main aspects for activity enhancement in the nickel phosphide-modified ZnO NRs. The optimized ZnO-Ni x P y nanocomposite exhibits an outstanding ammonia production rate of 2304.43 μmol h −1 g −1 without using any organic scavenger or precious noble metal. On the other hand, this catalyst also exhibits stupendous performance with a H 2 generation rate of 10 481 μmol h −1 g −1 using methanol as a hole scavenger. This magnificent result can be attributed to (i) Ni−P sites acting as active reaction sites for nitrogen and proton adsorption and activation, (ii) efficacious charge carrier segregation, and (iii) proficient charge transfer to the surface of nickel phosphide. This finding offers a new avenue for developing noble metalfree phosphide-based hybrids toward highly efficient photocatalytic reactions.

Hydrogen and oxygen evolution via photocatalytic water splitting remains the quintessential alternative to fossil fuels. Photocatalysts must be sufficiently robust, competent, and productive toward harnessing sunlight in order to utilize the solar spectrum for maximal photocatalytic output. Herein, we have fabricated the MgIn2S4/UiO-66-NH2 composite via a facile solvothermal route and have determined its efficacy toward light-induced H2 and O2 generation reactions through water splitting with the aid of different sacrificial agents. Initially, the formation of pristine and composite materials was ascertained by PXRD, FTIR, etc. Moreover, with the aid of sophisticated morphological characterization techniques (FESEM and HRTEM), the intricate interaction between MgIn2S4 and UiO-66-NH2 was revealed. Additionally, the XPS studies suggested the effective interaction between the individual components with binding energy shifting suggesting the transfer of electrons from Zr-MOF to MgIn2S4. The PL and electrochemical aspects supported the effective photogenerated charge segregation in the prepared composite leading to superior photocatalytic outputs. Amidst the prepared composites of (3, 5, and 7 wt %) MgIn2S4/UiO-66-NH2, the 5 wt % or UM-2 composite displays optimal H2 and O2 evolution performances of 493.8 and 258.6 μmol h–1 (4-fold greater than for pristine MgIn2S4 and UiO-66-NH2), respectively. The nanocomposite’s enhanced performance is indeed a consequence of the coadjuvant interaction among pristine UiO-66-NH2 and MgIn2S4 components that transpires via the Z-scheme-mediated charge transfer by enabling facile exciton segregation and channelization. Moreover, the composite inherited the remarkable framework stability of parent Zr-MOF, and the MgIn2S4 insertion had a negligible impact on the framework integrity. This work will offer a valuable model for developing robust Zr-MOF-based nanocomposite photocatalysts and evaluating their superior performance toward photocatalytic water redox reactions.