Morphology engineering has been recognized as an effective way to attain highly efficient and stable hybrid perovskite solar cells.

Solar-to-fuel conversion with organic-inorganic hybrid halide perovskites has attracted growing attention as a result of their excellent optoelectronic properties as well as the low temperature of the solution based fabrication process. However, the most comprehensively developed hybrid perovskite materials are comprised of the toxic metal lead, raising concerns about environmental health threats. Herein, a lead-free bismuth (Bi)-based hybrid perovskite showing in situ growth of heterojunctions is successfully developed at the interface of methylammonium bismuth iodide (MA 3 Bi 2 I 9) and tri(dimethylammonium) hexa-iodobismuthate (DMA 3 BiI 6) by a facile solvent engineering technique. The air-stable MA 3 Bi 2 I 9 /DMA 3 BiI 6 perovskite heterostructure with enhanced photoinduced charge separation exhibit outstanding visible-light-induced photocatalytic activity for H 2 evolution in aqueous hydrogen iodide solution. The powdered MA 3 Bi 2 I 9 /DMA 3 BiI 6 heterostructured composite (BBP-5) shows a H 2 evolution rate of 198.2 µmol h −1 g −1 without the addition of Pt co-catalysts under 100 mW cm −2 of visible-light (λ ≥ 420 nm) illumination.

The rational design of photocatalysts for efficient nitrogen (N 2 ) fixation at ambient conditions is important for revolutionizing ammonia production and quite challenging because the great difficulty lies in the adsorption and activation of the inert N 2 . Inspired by a biological molecule, chlorophyll, featuring a porphyrin structure as the photosensitizer and enzyme nitrogenase featuring an iron (Fe) atom as a favorable binding site for N 2 via π-backbonding, here we developed a porphyrin-based metal−organic framework (PMOF) with Fe as the active center as an artificial photocatalyst for N 2 reduction reaction (NRR) under ambient conditions. The PMOF features aluminum (Al) as metal node imparting high stability and Fe incorporated and atomically dispersed by residing at each porphyrin ring promoting the adsorption and the activation of N 2 , termed Al-PMOF(Fe). Compared with the pristine Al-PMOF, Al-PMOF(Fe) exhibits a substantial enhancement in NH 3 yield (635 μg g −1 cat. ) and production rate (127 μg h −1 g −1 cat. ) of 82% and 50%, respectively, on par with the best-performing MOF-based NRR catalysts. Three cycles of photocatalytic NRR experimental results corroborate a stable photocatalytic activity of Al-PMOF(Fe). The combined experimental and theoretical results reveal that the Fe−N site in Al-PMOF(Fe) is the active photocatalytic center that can mitigate the difficulty of the rate-determining step in photocatalytic NRR. The possible reaction pathways of NRR on Al-PMOF(Fe) were established. Our study of porphyrin-based MOF for the photocatalytic NRR will provide insight into the rational design of catalysts for artificial photosynthesis.

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To recover zirconium (Zr) from LiCl-KCl molten salt, the electro-reduction mechanisms and dynamic and thermodynamic properties of Zr­(IV) on W and Fe electrodes were investigated using a series of electrochemical techniques. Zr­(IV) was reduced by a continuous two-step process to form metallic Zr on the W electrode and a one-step process to form various Zr–Fe alloy compounds on the Fe film electrode. The deposition potentials pertaining to the formation of various Zr–Fe intermetallics were found more positive than those of Zr­(II)/Zr and Zr­(IV)/Zr­(II)­pairs. Furthermore, the dynamic data of the Zr­(II)/Zr pair on the W electrode and the ZrFe3/Zr­(IV) pair on the Fe film electrode were measured by linear polarization and Tafel methods. The results indicated that, with an increasing temperature, the value of the exchange current density for the two pairs increased, while the charge transfer resistance and transfer coefficient of the two pairs decreased. The thermodynamic data, for instance, the activities of Zr in Zr–Fe alloys and Gibbs free energies of the formation of Zr–Fe intermetallic compounds, were estimated using open-circuit chronopotentiometry. Furthermore, electrochemical recovering Zr was conducted using an Fe electrode by potentiostatic and galvanostatic electrolysis, which proved that the products were only ZrFe2 intermetallic compounds. The recovery efficiencies were 98.05% and 98.97%, respectively.

For the first time, we demonstrate that 2D layered (MA)2CdCl4-based perovskite photoelectrodes show photoelectrochemical response with enhanced long-term stability.