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      Vertically oriented cobalt selenide/NiFe layered-double-hydroxide nanosheets supported on exfoliated graphene foil: an efficient 3D electrode for overall water splitting

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          Abstract

          A 3D ternary hybrid containing Co 0.85Se nanosheet-array and NiFe-LDH grown on electrochemically exfoliated graphene was synthesized for highly-efficient overall water-splitting.’

          Abstract

          Developing cost-effective electrocatalysts for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in basic media is critical to renewable energy conversion technologies. Here, we report a ternary hybrid that is constructed by in situ growth of cobalt selenide (Co 0.85Se) nanosheets vertically oriented on electrochemically exfoliated graphene foil, with subsequent deposition of NiFe layered-double-hydroxide by a hydrothermal treatment. The resulting 3D hierarchical hybrid, possessing a high surface area of 156 m 2 g −1 and strong coupling effect, exhibits excellent catalytic activity for OER, which only requires overpotentials of 1.50 and 1.51 V to attain current densities of 150 and 250 mA cm −2, respectively. These overpotentials are much lower than those reported for other non-noble-metal materials and Ir/C catalysts. The hybrid also efficiently catalyzes HER in base with a current density of 10 mA cm −2 at an overpotential of −0.26 V. Most importantly, we achieve a current density of 20 mA cm −2 at 1.71 V by using the 3D hybrid as both a cathode and an anode for overall water splitting, which is well comparable to the integrated performance of Pt/C and Ir/C catalysts.

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          A perovskite oxide optimized for oxygen evolution catalysis from molecular orbital principles.

          The efficiency of many energy storage technologies, such as rechargeable metal-air batteries and hydrogen production from water splitting, is limited by the slow kinetics of the oxygen evolution reaction (OER). We found that Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-δ) (BSCF) catalyzes the OER with intrinsic activity that is at least an order of magnitude higher than that of the state-of-the-art iridium oxide catalyst in alkaline media. The high activity of BSCF was predicted from a design principle established by systematic examination of more than 10 transition metal oxides, which showed that the intrinsic OER activity exhibits a volcano-shaped dependence on the occupancy of the 3d electron with an e(g) symmetry of surface transition metal cations in an oxide. The peak OER activity was predicted to be at an e(g) occupancy close to unity, with high covalency of transition metal-oxygen bonds.
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            Water photolysis at 12.3% efficiency via perovskite photovoltaics and Earth-abundant catalysts.

            Although sunlight-driven water splitting is a promising route to sustainable hydrogen fuel production, widespread implementation is hampered by the expense of the necessary photovoltaic and photoelectrochemical apparatus. Here, we describe a highly efficient and low-cost water-splitting cell combining a state-of-the-art solution-processed perovskite tandem solar cell and a bifunctional Earth-abundant catalyst. The catalyst electrode, a NiFe layered double hydroxide, exhibits high activity toward both the oxygen and hydrogen evolution reactions in alkaline electrolyte. The combination of the two yields a water-splitting photocurrent density of around 10 milliamperes per square centimeter, corresponding to a solar-to-hydrogen efficiency of 12.3%. Currently, the perovskite instability limits the cell lifetime.
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              An advanced Ni-Fe layered double hydroxide electrocatalyst for water oxidation.

              Highly active, durable, and cost-effective electrocatalysts for water oxidation to evolve oxygen gas hold a key to a range of renewable energy solutions, including water-splitting and rechargeable metal-air batteries. Here, we report the synthesis of ultrathin nickel-iron layered double hydroxide (NiFe-LDH) nanoplates on mildly oxidized multiwalled carbon nanotubes (CNTs). Incorporation of Fe into the nickel hydroxide induced the formation of NiFe-LDH. The crystalline NiFe-LDH phase in nanoplate form is found to be highly active for oxygen evolution reaction in alkaline solutions. For NiFe-LDH grown on a network of CNTs, the resulting NiFe-LDH/CNT complex exhibits higher electrocatalytic activity and stability for oxygen evolution than commercial precious metal Ir catalysts.
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                Author and article information

                Journal
                EESNBY
                Energy & Environmental Science
                Energy Environ. Sci.
                Royal Society of Chemistry (RSC)
                1754-5692
                1754-5706
                2016
                2016
                : 9
                : 2
                : 478-483
                Article
                10.1039/C5EE03440J
                bc25f423-9787-458b-adac-5474a627e2b4
                © 2016
                History

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