Fulin Yang

A cobalt-based hybrid electrocatalyst derived from a carbon nanotube inserted metal–organic framework for efficient water-splitting

The design of high-efficiency non-precious electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is extremely important for developing sustainable energy technologies. Herein, we report a metal–organic framework (MOF) template carbonization route to prepare a Co-based hybrid electrocatalyst with superior performance for both HER and OER in an alkaline solution. Starting from a carbon nanotube (CNT) inserted Co MOF, the Co-NC/CNT hybrid with a N-doped carbon nanoframe composed of hollow Co nanoparticles interlinked by CNTs is first synthesized via carbonization. This unique 3D structure is shown to have highly exposed active sites and good conductivity. Most importantly, the Co-NC/CNT hybrid can act as bifunctional catalysts on both anode and cathode for electrochemical water splitting, to deliver a current density of 10 mA cm−2 under a cell voltage as low as 1.625 V.

Reduced Graphene Oxide‐Wrapped Co9–xFexS8/Co,Fe‐N‐C Composite as Bifunctional Electrocatalyst for Oxygen Reduction and Evolution

Searching for highly efficient bifunctional electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) using nonnoble metal-based catalysts is essential for the development of many energy conversion systems, including rechargeable fuel cells and metal-air batteries. Here, Co9-x Fex S8 /Co,Fe-N-C hybrids wrapped by reduced graphene oxide (rGO) (abbreviated as S-Co9-x Fex S8 @rGO) are synthesized through a semivulcanization and calcination method using graphene oxide (GO) wrapped bimetallic zeolite imidazolate framework (ZIF) Co,Fe-ZIF (CoFe-ZIF@GO) as precursors. Benefiting from the synergistic effect of OER active CoFeS and ORR active Co,Fe-N-C in a single component, as well as high dispersity and enhanced conductivity derived from rGO coating and Fe-doping, the obtained S-Co9-x Fex S8 @rGO-10 catalyst shows an ultrasmall overpotential of ≈0.29 V at 10 mA cm-2 in OER and a half-wave potential of 0.84 V in ORR, combining a superior oxygen electrode activity of ≈0.68 V in 0.1 m KOH.

Ir-oriented nanocrystalline assemblies with high activity for hydrogen oxidation/evolution reactions in an alkaline electrolyte

In this study, we report successful synthesis of ultrafine worm-like Ir-oriented nanocrystalline assemblies (ONAs) and their further use as efficient electrocatalysts towards the HOR/HER in an alkaline medium. Due to the fast mass/charge transfer rate as well as the appearance of the long segments of low-index crystalline planes, the as-synthesized Ir ONAs exhibit a remarkable performance for the HOR/HER in an alkaline electrolyte.

Construction of a hierarchical NiFe layered double hydroxide with a 3D mesoporous structure as an advanced electrocatalyst for water oxidation

The exploitation of highly active, cost-effective, and stable electrocatalysts toward the oxygen evolution reaction (OER) is essential for the development of various energy conversion and storage systems, such as water splitting and metal–air batteries. In this report, 3D mesoporous NiFe layered double hydroxide (LDH) microclusters with a hierarchical architecture are in situ grown on Ni foam through a facile and cost-effective one-step hydrothermal method by using Ni foam as both a Ni source and support. Thanks to the unique architecture and strong synergistic electronic effect between Ni and Fe, the as-synthesized NiFe LDH exhibits remarkable catalytic OER performance with a small overpotential of 211 mV to achieve a current density of 10 mA cm−2, which outperforms most of the reported non-noble metal-based catalysts and almost all the documented LDH-based electrocatalysts.

Monodisperse Palladium Sulfide as Efficient Electrocatalyst for Oxygen Reduction Reaction

In this study, we report a colloidal synthesis of palladium sulfides (including Pd16S7, Pd4S, and PdS) via a facile one-pot hot-solution synthetic route and their promising application as electrocatalyst for the oxygen reduction reaction (ORR). Among the different palladium sulfides tested, monodisperse Pd4S nanoparticles exhibit the best electrocatalytic activity toward ORR in alkaline medium, with the half-wave potential ca. 47 mV more positive than that of the state-of-the-art Pt/C catalyst. Density functional theory calculations indicate the existence of oxygen absorption sites in Pd4S surface result in optimized oxygen-binding ability for the four-electron oxygen reduction.

Well-aligned metal–organic framework array-derived CoS2 nanosheets toward robust electrochemical water splitting

Exploring high-efficiency and stable nonprecious bifunctional electrocatalysts for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) is highly desirable but still challenging. Herein, we develop a versatile approach for the rational design and fabrication of highly open three-dimensional (3D) hierarchical architectures composed of two-dimensional (2D) CoS2 nanosheets grown on carbon cloth (CoS2 NS/CC) by vulcanizing well-aligned MOF-array precursors. Benefiting from the unique morphology with a high surface area, high density of active sites, and enhanced mass/electrolyte transfer, as well as facile release of the evolved gas, the as-synthesized CoS2 NS/CC exhibits superior catalytic performance and excellent durability for both the HER and OER. Furthermore, when used as a bifunctional electrocatalyst toward overall water splitting, a low cell voltage of 1.58 V is achieved at the current density of 10 mA cm−2 with long-term stability.

Carbon Encapsulated Hollow Co3O4 Composites Derived from Reduced Graphene Oxide Wrapped Metal–Organic Frameworks with Enhanced Lithium Storage and Water Oxidation Properties

Transition metal oxides have received great attention for boosting the performances for lithium-ion batteries and oxygen evolution reaction (OER). Here, hollow Co3O4 nanoparticles encapsulated in reduced graphene oxide (rGO) ( h-Co3O4@rGO) were synthesized through a two-step annealing process of graphene oxide wrapped zeolitic imidazolate framework-67 (ZIF-67@GO) precursors. By taking advantage of the enhanced conductivity, high dispersity, high surface area, and unique hollow morphology derived from the GO-wrapped protecting annealing strategy, the as-synthesized h-Co3O4@rGO composite not only exhibits a reversible capacity as high as 1154.2 mAh g-1 at 500 mA g-1 after 100 cycles and high rate performance (746 mAh g-1 at 3000 mA g-1) but also displays superior OER performance with an overpotential of 300 mV to obtain 10 mA cm-2.