One-pot synthesis of crystalline structure: Nickel-iron phosphide and selenide for hydrogen production in alkaline water splitting

Electrocatalytically active nanocomposites play a vital role in energy generation, conversion, and storage technologies. Transition metal-based catalysts such as nickel and iron and their pnictide (phosphide), and chalcogenide (selenide) compounds exhibit good activity for hydrogen evolution reaction (HER) in the alkaline environment. In this study, transition metals-based catalysts (Ni-P-Se, Fe-P-Se, and Ni-Fe-P-Se) solutions were prepared using a simple one-pot method. Prepared solutions were deposited on Ni foam, and different characterization techniques were used to determine the composition, structure, and morphology of as-prepared catalysts. Furthermore, it was found that Ni-Fe-P-Se as a cathode material showed better HER performance compared to other investigated materials with the overpotential value of 316 mV at 10 mA cm-2 current density and 89 mV dec-1 Tafel slope value. The stability tests of the as-prepared catalyst confirmed that the synergistic effect between various elements enhances the electrocatalytic performance for up to 24 hours, providing a fair, stable nature of Ni-Fe-P-Se based sample

Structural and Electronic Properties of (HfH2)(n) (n=5-30) Clusters: Theoretical Investigation

Metallic hydride clusters have greater importance due to its unique physicomechanical properties. For solid-state hydrogen storage, (HfH2)(n) clusters has been considered a promising candidate because of high hydrogen capacity, low cost and larger interacting affinity between atoms. The structural and electronic properties of (HfH2)(n), clusters are investigated by employing the density functional theory. From the DFT calculations, it is found that Hf atom occupies central position while H atoms tends to occupy at vertex spots. Through structural stability analysis, the calculated binding energy and second order energy difference of (HfH2)(n) clusters increases from (HfH2)(5) through (HfH2)(30). The charge density distribution and results of Bader analysis revealed ionic bonding character between Hf and H atoms and transfer of electrons is observed from Hf to H atoms. The orbital overlapping contribution of the interacting Hf and H atom is also performed

Insights into structural and electronic properties of (LiH)n (n=5-25) clusters: Density functional calculations

First principles calculations have been performed to analyze the structural and electronic properties of (LiH)n clusters by combining an artificial bee colony algorithm within the framework of Density Functional Theory (DFT). The structural analysis shows that with an increase in cluster size, the structural shape tends to become more amorphous in which the lithium (Li) atom occupies the central position, surrounded by hydrogen (H) atoms at the vertex sites. The bond length between Li and H was found to be 1.77-2.01 angstrom, which is in good agreement with the previous study. Through stability analysis, the calculated formation energy of LiH clusters increase from n = 5 through n = 25. The projected density of states was calculated and analyzed to get deeper insight of the electronic structure. The charge density distribution and results of density derived electrostatic and chemical (DDEC6) analysis revealed ionic bonding characteristics between Li and H atoms, and charge density difference analysis concludes electron transfers from Li to H atoms

Insights into structural and electronic properties of (LiH)n (n=5-25) clusters: Density functional calculations

First principles calculations have been performed to analyze the structural and electronic properties of (LiH)n clusters by combining an artificial bee colony algorithm within the framework of Density Functional Theory (DFT). The structural analysis shows that with an increase in cluster size, the structural shape tends to become more amorphous in which the lithium (Li) atom occupies the central position, surrounded by hydrogen (H) atoms at the vertex sites. The bond length between Li and H was found to be 1.77-2.01 angstrom, which is in good agreement with the previous study. Through stability analysis, the calculated formation energy of LiH clusters increase from n = 5 through n = 25. The projected density of states was calculated and analyzed to get deeper insight of the electronic structure. The charge density distribution and results of density derived electrostatic and chemical (DDEC6) analysis revealed ionic bonding characteristics between Li and H atoms, and charge density difference analysis concludes electron transfers from Li to H atoms

CoSe2@Co3O4 nanostructures: A promising catalyst for oxygen evolution reaction in alkaline media

Synergistic integration based on some transition-metal (TM) derived compounds is a unique and appealing technique, especially toward oxygen evolution reaction (OER) under alkaline circumstances. Herein, we present a cobalt-selenide (CoSe2) and cobalt-oxide (Co3O4) based composite (CSCO-2) material through a wet chemical method. As-prepared catalyst has been analyzed for various physicochemical characterizations. CSCO-2 offers efficient OER performance in 1.0 M KOH with an overpotential of 252 mV at current density of 20 mA/cm2, with a low Tafel slope value of 69 mV/dec. Importantly, as-prepared catalyst shows stability of 48 h for longer electrochemical performance as a potential candidate for OER

Electrochemical performance of grown layer of Ni(OH)2 on nickel foam and treatment with phosphide and selenide for efficient water splitting

Active nanocomposites synthesized by the electrochemical approach play a vital role in energy generation, conversion, and storage technologies. Recently, scientists began to explore the use of earth-rich transition metalbased materials to replace precious metal-based catalysts. Transition metals (TMs) based nickel (Ni) and their pnictides compounds such as phosphides and selenides exhibit good activity for hydrogen evaluation reaction (HER) and the entire water electrolysis process. In this study, we first prepared Ni(OH)2 and grown its layer on Ni foam (NF) and treated it with selenide (Se) and phosphide (P) then nickel-based selenide-phosphide catalyst (Ni-P-Se) was prepared by simultaneous selenization and phosphidation process for the first time. The asobtained composite was then analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM), elemental mapping and transmission electron microscope (TEM) means to study the composition, structure, and micro-morphology of materials. Furthermore, we also observed electrocatalytic water splitting activity using electrochemical cell. The results of electrochemical tests depicted that the selenization and phosphidation treatments significantly enhanced the electrocatalytic HER activity of the starting materials. The overpotentials required for Ni-P-Se to reach 10 mA cm-2 and 100 mA cm-2 were only 242 mV and 282 mV. The Tafel slope of Ni-P-Se is 151 mV dec-1, which is lower than that of nickel phosphide, selenide, and hydroxide indicating that selenide-phosphide enhances the HER reaction kinetics of the material, which in turn increases hydrogen output rate as compared with previous studies

Electrochemical performance of grown layer of Ni(OH)2 on nickel foam and treatment with phosphide and selenide for efficient water splitting

Active nanocomposites synthesized by the electrochemical approach play a vital role in energy generation, conversion, and storage technologies. Recently, scientists began to explore the use of earth-rich transition metalbased materials to replace precious metal-based catalysts. Transition metals (TMs) based nickel (Ni) and their pnictides compounds such as phosphides and selenides exhibit good activity for hydrogen evaluation reaction (HER) and the entire water electrolysis process. In this study, we first prepared Ni(OH)2 and grown its layer on Ni foam (NF) and treated it with selenide (Se) and phosphide (P) then nickel-based selenide-phosphide catalyst (Ni-P-Se) was prepared by simultaneous selenization and phosphidation process for the first time. The asobtained composite was then analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM), elemental mapping and transmission electron microscope (TEM) means to study the composition, structure, and micro-morphology of materials. Furthermore, we also observed electrocatalytic water splitting activity using electrochemical cell. The results of electrochemical tests depicted that the selenization and phosphidation treatments significantly enhanced the electrocatalytic HER activity of the starting materials. The overpotentials required for Ni-P-Se to reach 10 mA cm-2 and 100 mA cm-2 were only 242 mV and 282 mV. The Tafel slope of Ni-P-Se is 151 mV dec-1, which is lower than that of nickel phosphide, selenide, and hydroxide indicating that selenide-phosphide enhances the HER reaction kinetics of the material, which in turn increases hydrogen output rate as compared with previous studies

PdO@CoSe2 composites: efficient electrocatalysts for water oxidation in alkaline media

In this study, we have prepared cobalt selenide (CoSe2) due to its useful aspects from a catalysis point of view such as abundant active sites from Se edges, and significant stability in alkaline conditions. CoSe2, however, has yet to prove its functionality, so we doped palladium oxide (PdO) onto CoSe2 nanostructures using ultraviolet (UV) light, resulting in an efficient and stable water oxidation composite. The crystal arrays, morphology, and chemical composition of the surface were studied using a variety of characterization techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectroscopy. It was also demonstrated that the composite systems were heterogeneous in their morphology, undergoing a shift in their diffraction patterns, suffering from a variety of metal oxidation states and surface defects. The water oxidation was verified by a low overpotential of 260 mV at a current density of 20 mA cm(-2) with a Tafel Slope value of 57 mV dec(-1). The presence of multi metal oxidation states, rich surface edges of Se and favorable charge transport played a leading role towards water oxidation with a low energy demand. Furthermore, 48 h of durability is associated with the composite system. With the use of PdO and CoSe2, new, low efficiency, simple electrocatalysts for water catalysis have been developed, enabling the development of practical energy conversion and storage systems. This is an excellent alternative approach for fostering growth in the field.Funding Agencies|Ajman University [2022-IRG-HBS-5]; National Natural Science Foundation of China [NSFC 51402065, 51603053]</p