4 research outputs found

    In Situ Fabrication of Ni–Mo Bimetal Sulfide Hybrid as an Efficient Electrocatalyst for Hydrogen Evolution over a Wide pH Range

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    Electrochemical water splitting to produce hydrogen bears a great commitment for future renewable energy conversion and storage. By employing an in situ chemical vapor deposition (CVD) process, we prepared a bimetal (Ni and Mo) sulfide-based hybrid nanowire (NiS<sub>2</sub>/MoS<sub>2</sub> HNW), which was composed of NiS<sub>2</sub> nanoparticles and MoS<sub>2</sub> nanoplates, and revealed that it is an efficient electrocatalyst for the hydrogen evolution reaction (HER) over a wide pH range due to the collective effects of rational morphological design and synergistic heterointerfaces. On a simple glassy carbon (GC) electrode, NiS<sub>2</sub>/MoS<sub>2</sub> HNW displays overpotentials at −10 mA cm<sup>–2</sup> catalytic current density (η<sub>10</sub>) of 204, 235, and 284 mV with small Tafel slopes of 65, 58, and 83 mV dec<sup>–1</sup> in alkaline, acidic, and neutral electrolyte, respectively, exhibiting pH-universal-efficient electrocatalytic HER performance, which is comparable to the recently reported state-of-the-art sulfide-based HER electrocatalysts. Theoretical calculations further confirm that the advantage of all-pH HER activity of NiS<sub>2</sub>/MoS<sub>2</sub> originates from the enhanced dissociation of H<sub>2</sub>O induced by the formation of lattice interfaces of NiS<sub>2</sub>–MoS<sub>2</sub> heterojunctions. This work can pave a valuable route for designing and fabricating inexpensive and high-performance electrocatalysts toward HER over a wide pH range

    Metal–Organic Framework-Derived Nickel–Cobalt Sulfide on Ultrathin Mxene Nanosheets for Electrocatalytic Oxygen Evolution

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    Water oxidation is the key process for many sustainable energy technologies containing artificial photosynthesis and metal–air batteries. Engineering inexpensive yet active electrocatalysts for water oxidation is mandatory for the cost-effective generation of solar fuels. Herein, we propose a novel hierarchical porous Ni–Co-mixed metal sulfide (denoted as NiCoS) on Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> MXene via a metal–organic framework (MOF)-based approach. Benefiting from the unique structure and strong interfacial interaction between NiCoS and Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> sheets, the hybrid guarantees an enhanced active surface area with prominent charge-transfer conductivity and thus a superior activity toward oxygen evolution reactions (OERs). Impressively, the hierarchical NiCoS in the hybrid is converted to nickel/cobalt oxyhydroxide–NiCoS assembly (denoted as NiCoOOH–NiCoS) by OER measurement, where NiCoOOH on the surface is confirmed as the intrinsic active species for the consequent water oxidation. The hybrid material is further applied to an air cathode for a rechargeable zinc–air battery, which exhibits low charging/discharging overpotential and long-term stability. Our work underscores the tuned structure and electrocatalytic OER performance of MOF derivatives by the versatility of MXenes and provides insight into the structure–activity relationship for noble metal-free catalysts

    Immobilizing Ru(bda) Catalyst on a Photoanode via Electrochemical Polymerization for Light-Driven Water Splitting

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    The molecular water oxidation catalyst <b>1</b> was electrochemically polymerized on a dye-sensitized TiO<sub>2</sub> electrode and an Fe<sub>2</sub>O<sub>3</sub> nanorod electrode. High photocurrent densities of ca. 1.4 mA cm<sup>–2</sup> for poly-<b>1</b>+<b>RuP</b>@TiO<sub>2</sub> and ca. 0.4 mA cm<sup>–2</sup> for poly-<b>1</b>@Fe<sub>2</sub>O<sub>3</sub> were achieved under pH-neutral conditions. A kinetic isotope effect (KIE) study on poly-<b>1</b>+<b>RuP</b>@TiO<sub>2</sub> shows that poly-<b>1</b> catalyzes water oxidation on the surface of TiO<sub>2</sub> via a radical coupling mechanism

    Improvement of the SiO<sub><i>x</i></sub> Passivation Layer for High-Efficiency Si/PEDOT:PSS Heterojunction Solar Cells

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    Interfacial properties currently hinder the performance of Si/organic heterojunction solar cells for an alternative to high-efficiency and low-cost photovoltaics. Here, we present a simple and repeatable wet oxidation method for developing the surface passivation layer, SiO<sub><i>x</i></sub>, on the Si surface for the fabrication of high-efficiency Si/poly­(3,4-ethylene-dioxythiophene):polystyrenesulfonate (PEDOT:PSS) heterojunction solar cells. The uniform and dense SiO<sub><i>x</i></sub> thin layer introduced by the oxidizing aqueous solution of H<sub>2</sub>O<sub>2</sub> or HNO<sub>3</sub> provided the better surface passivation and stronger wettability of the Si surface, compared to those in the native oxide case. These two types of progress helped create a lower defect density at the Si/PEDOT:PSS interface and thus a high-quality p–n junction with a lower interface recombination velocity. As a result, the HNO<sub>3</sub>-oxidized device displayed better performance with a power conversion efficiency (PCE) of 11%, representing a 28.96% enhancement from the PCE of 8.53% in the native oxide case. The effects on the performance of the Si/PEDOT:PSS hybrid solar cells of the wet oxidation treatment procedure, including the differences in surface roughness and wettability of the Si substrate, the quality and thickness of the SiO<sub><i>x</i></sub>, etc., were explored extensively. Such a simple and controllable oxidizing treatment could be an effective way to promote the interfacial properties that are an important cornerstone for more efficient Si/organic hybrid solar cells