An Efficient, Visible‐Light‐Driven, Hydrogen Evolution Catalyst NiS/Zn_xCd_1−xS Nanocrystal Derived from a Metal–Organic Framework

Abstract

Photocatalytic water splitting for hydrogen production using sustainable sunlight is a promising alternative to industrial hydrogen production. However, the scarcity of highly active, recyclable, inexpensive photocatalysts impedes the development of photocatalytic hydrogen evolution reaction (HER) schemes. Herein, a metal–organic framework (MOF)‐template strategy was developed to prepare non‐noble metal co‐catalyst/solid solution heterojunction NiS/ZnxCd1−xS with superior photocatalytic HER activity. By adjusting the doping metal concentration in MOFs, the chemical compositions and band gaps of the heterojunctions can be fine‐tuned, and the light absorption capacity and photocatalytic activity were further optimized. NiS/Zn0.5Cd0.5S exhibits an optimal HER rate of 16.78 mmol g−1 h−1 and high stability and recyclability under visible‐light irradiation (λ>420 nm). Detailed characterizations and in‐depth DFT calculations reveal the relationship between the heterojunction and photocatalytic activity and confirm the importance of NiS in accelerating the water dissociation kinetics, which is a crucial factor for photocatalytic HER.

Shielded goethite catalyst that enables fast water dissociation in bipolar membranes

“…The DFT calculations confirm that the goethite catalyst lowers the activation energy barrier of water dissociation from 5.15 eV (in water and without WD catalyst) 36 to only 1.06 eV per OH-H bond at the transition state. Although the barrier lowering is not as significant as with Pt(111), Fe-MoS 2 , NiFe-LDH, MoO 2 and other famous catalysts, the catalytic activity of the goethite is sufficiently better than several pristine catalytic materials such as Zn 0.5 Cd 0.5 S, Cu 7 , MoS 2 and pristine copper [26][27][28][29][30][31][32] , which is certainly a great achievement. Most importantly, successful first-time use of the goethite Fe +3 O (OH) catalyst in bipolar membranes for achieving energy-efficient water dissociation, indicates the significance of the present research work and importance of the produced catalyst in both the scientific and applied research.…”

“…Water adsorption and dissociation are both found at the terminated Fe +3 site and the corresponding Gibbs free energies are calculated for H 2 O adsorption (ΔG: 0.00 eV), the transition (ΔG: 1.06 eV) and the hydrolyzation (ΔG: −1.48 eV) states, respectively. Assuming zero effect of the externally applied reverse biased electric field (same as in literature and the DFT calculations in this work, all cif files that are used in the DFT calculations are provided as Supplementary Data 1) [26][27][28][29][30][31][32] , we have also calculated the relative energies to release the produced H + (as H 3 O + ) and OH − from the catalyst surface (ΔG release : 5.06 eV, Supplementary Fig. 18b).…”

“…However, the role of the electric field (second Wein effect) is always considered beneficial for WD as well as in releasing H + (as H 3 O + ) and OH − from the catalyst surface and the junction [33][34][35] . Because the literature generally gives a comparison of the energies at the transition state by considering this as a fundamental energy barrier that is necessary to lower using various catalysts [26][27][28][29][30][31][32][33] . Therefore, we have compared the DFT-calculated energy barrier of the goethite Fe +3 O(OH) catalyst at the transition state with the literature (Fig.…”

Polarity‐Induced Excited‐State Intramolecular Proton Transfer (ESIPT) in a Pair of Supramolecular Isomeric Multifunctional Dynamic Metal–Organic Frameworks

“…[4,14,15] Many naturally occurring organic molecules as well as some synthetic derivatives have been found to be excellent candidates for ESIPT study, [17,18] although such materials have limited practicala pplicationsd ue to their low emission efficiency,s tability,c oncentration quenching, and solution-statep roperties. [4] MOFs, as ac lass of crystalline microporous materials, are already highly celebrated due to their structure-property relationships, [21,22] which enables versatile applicationsi naw ide rangeo ff ields, including gas adsorption/storage, [23,24] electrical devices, [25,26] catalysis, [27][28][29] ion exchange, [30,31] and magnetic materials. [18,19] Thus,a tmospherically stable metal-organic frameworks (MOFs) bearing an ESIPT fluorophore and d 10 metal nodes perhaps have the most potential due to their insoluble naturei nc ommon organic solvents.…”

“…[18,19] Thus,a tmospherically stable metal-organic frameworks (MOFs) bearing an ESIPT fluorophore and d 10 metal nodes perhaps have the most potential due to their insoluble naturei nc ommon organic solvents. [4] MOFs, as ac lass of crystalline microporous materials, are already highly celebrated due to their structure-property relationships, [21,22] which enables versatile applicationsi naw ide rangeo ff ields, including gas adsorption/storage, [23,24] electrical devices, [25,26] catalysis, [27][28][29] ion exchange, [30,31] and magnetic materials. [32,33] In addition, flexible MOFs responsive to externals timuli [34,35] may be utilizedt of abricate excellentd evices relatedt os ensing, [4,36] data storage, [37] and molecular switches, [38] although some rigid MOFs, with or without ESIPT behavior,h ave also been found to be very suitable for sensing applications.…”