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The adoption of effective, minimal, and versatile electrocatalysts for water splitting to generate hydrogen fuels is of critical importance. The bulk of newly described materials have considerable onset potential, but their electrocatalytic activity is limited by weak electrical conductivity and a limited range of catalytic sites. The combination of a few precious metals added with transition metal-based compounds is a novel and captivating approach. Herein, cobalt ferrite oxide (Co 2 FeO 4) @ palladium oxide (PdO) nanostructures have been prepared through the combined use of hydrothermal and ultraviolet (UV) irradiation techniques. For hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) kinetics, the modified composition offers a high concentration of active sites, improved electrical conductivity, and stability. The Co, Fe, and Pd ions at the composite system's interface may affect the adsorption energy of reaction intermediates synergistically, enabling the process to continue with less potential. The electrocatalyst Co 2 FeO 4 @PdO demonstrates an excellent bifunctional approach to electrochemical water splitting (EWS) for HER and OER in alkaline medium. As-prepared electrocatalyst shows an overpotential value of 269 and 259 mV for HER and OER at 10 and 20 mA/cm2 current densities respectively. The low charge transfer resistance values such as 72.2 and 62.4 Ω and durability for 48 h has been observed toward HER and OER , support this material as an efficient and durable electrocatalyst for energy conversion systems. [Display omitted] • Effective Cobalt–Iron-Ferrite oxides and Palladium-oxide based bifunctional electrocatalyst. • Promising activity for HER and OER with lower Tafel slope values in the alkaline media. • Longer stability and durability for 20 h. [ABSTRACT FROM AUTHOR]

Development of efficient, low cost and multifunctional electrocatalysts for water splitting to harvest hydrogen fuels is a challenging task, but the combination of carbon materials with transition metal-based compounds is providing a unique and attractive strategy. Herein, composite systems based on cobalt ferrite oxide-reduced graphene oxide (Co 2 FeO 4) @(rGO) using simultaneous hydrothermal and chemical reduction methods have been prepared. The proposed study eliminates one step associated with the conversion of GO into rGO as it uses direct GO during the synthesis of cobalt ferrite oxide, consequently rGO based hybrid system is achieved in-situ significantly, the optimized Co 2 FeO 4 @rGO composite has revealed an outstanding multifunctional applications related to both oxygen evolution reaction (OER) and hydrogen counterpart (HER). Various metal oxidation states and oxygen vacancies at the surface of Co 2 FeO 4 @rGO composites guided the multifunctional surface properties. The optimized Co 2 FeO 4 @rGO composite presents excellent multifunctional properties with onset potential of 0.60 V for ORR, an overpotential of 240 mV at a 20 mAcm−2 for OER and 320 mV at a 10 mAcm−2 for HER respectively. Results revealed that these multifunctional properties of the optimized Co 2 FeO 4 @ rGO composite are associated with high electrical conductivity, high density of active sites, crystal defects, oxygen vacancies, and favorable electronic structure arisinng from the substitution of Fe for Co atoms in binary spinel oxide phase. These surface features synergistically uplifted the electrocatalytic properties of Co 2 FeO 4 @rGO composites. The multifunctional properties of the Co 2 FeO 4 @ rGO composite could be of high interest for its use in a wide range of applications in sustainable and renewable energy fields. Illustration of multifunctional surface properties of Co 2 FeO 4 @rGO composite. [Display omitted] • In situ rGO and cobalt ferrite oxide (Co 2 FeO 4 @rGO) composite is prepared. • The synthesized composite exhibited tri-functional water catalysis. • Composite shows an overpotential of 240 mV at a 20 mAcm−2 for OER. • A long term durability of 48 h was also demonstrated by composite material. [ABSTRACT FROM AUTHOR]

Herein, the vertical thin nickel–iron layered double hydroxide nanosheets grown on the hills-like nickel framework (NiFe LDH/Ni@NF) are employed for the oxygen evolution reaction (OER), securing at the low overpotentials of 197 and 270 mV to obtain the current densities of 20 and 100 mA cm−2, respectively, with a Tafel slope of 73.34 mV dec−1. The electrodeposited nickel film induces the NiFe LDH nanosheets grow vertically and thinly. As well, the nickel abundant interfaces and inner space makes this catalyst effective for OER. It was further served as the OER electrode in a water splitting system coupled the Pt/C cathode, and a cell voltage was at 1.52 and 1.67 V to achieve the current density of 10 mA cm−2 and 50 mA cm−2. In addition, the water electrolyzer can suffer a long time of 24 h at 50 mA cm−2, showing the feasibility in a practical unbiased alkaline water splitting system. • The vertical thin Ni 4 Fe 1 LDH-16h was prepared on the hills-like nickel framework. • The crosslinked nanosheets can offer amounts of active sites for OER. • It achieves a low overpotential of 197 mV to drive 20 mA cm−2 for OER. • The assembled electrolyzer exhibits enhanced performance. [ABSTRACT FROM AUTHOR]

In this paper, we report the three-dimensional self-supported CoMoO 4 nanosheet clusters on the nickel foam (denoted as CoMoO 4 /NF) by a facile hydrothermal-calcination method for efficient hydrogen generation. As a result, the freestanding CoMoO 4 electrode exhibits an efficient electrochemical activity towards hydrogen evolution reaction, showing overpotentials as low as 68 and 178 mV at current densities of 10 and 100 mA cm−2 in the alkaline condition (1 M KOH), respectively, a Tafel slope value of 82 mV per decade. Moreover, the electrode exhibits remarkable electrochemical durability for 1000 cycles. Significantly, the water splitting electrolyzer assembled with CoMoO 4 /NF || NiFe LDH/NF (the nickel iron layered double hydroxide supported on the nickel foam) system achieved 20 mA cm−2 at 1.63 V, showing the CoMoO 4 /NF is promising for practical water splitting applications. • The low-cost and effective transition metal oxide of CoMoO 4 was adopted for hydrogen generation. • The open nanostructure can facilitate permeating electrolyte as well as releasing hydrogen molecules. • The crosslinked nanosheet clusters can offer amounts of active sites for hydrogen evolution reaction. [ABSTRACT FROM AUTHOR]