Project description:For efficient electrolysis of water for hydrogen generation or other value-added chemicals, it is highly relevant to develop low-temperature synthesis of low-cost and high-efficiency metal sulfide electrocatalysts on a large scale. Herein, we construct a new core-branch array and binder-free electrode by growing Ni3S2 nanoflake branches on an atomic-layer-deposited (ALD) TiO2 skeleton. Through induced growth on the ALD-TiO2 backbone, cross-linked Ni3S2 nanoflake branches with exposed {[Formula: see text]} high-index facets are uniformly anchored to the preformed TiO2 core forming an integrated electrocatalyst. Such a core-branch array structure possesses large active surface area, uniform porous structure, and rich active sites of the exposed {[Formula: see text]} high-index facet in the Ni3S2 nanoflake. Accordingly, the TiO2@Ni3S2 core/branch arrays exhibit remarkable electrocatalytic activities in an alkaline medium, with lower overpotentials for both oxygen evolution reaction (220 mV at 10 mA cm-2) and hydrogen evolution reaction (112 mV at 10 mA cm-2), which are better than those of other Ni3S2 counterparts. Stable overall water splitting based on this bifunctional electrolyzer is also demonstrated.
Project description:Design and synthesis of electrocatalysts with high activity and low cost is an important challenge for water splitting. We report a rapid and facile synthetic route to obtain Ir x Ni clusters via polyol reduction. The Ir x Ni clusters show excellent activity for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in acidic electrolytes. The optimized Ir2Ni/C clusters exhibit an electrochemical active area of 18.27 mF cm-2, with the overpotential of OER being 292 mV and HER being 30 mV at 10 mA cm-2, respectively. In addition, the Ir2Ni/C used as the cathode and anode for the H-type hydrolysis tank only needs 1.597 V cell voltages. The excellent electrocatalytic performance is mainly attributed to the synergistic effect between the metals and the ultra-fine particle size. This study provides a novel strategy that has a broad application for water splitting.
Project description:Rational design of efficient bifunctional electrocatalysts is highly imperative but still a challenge for overall water splitting. Herein, we construct novel freestanding Mo-doped NiCoP nanosheet arrays by the hydrothermal and phosphation processes, serving as bifunctional electrocatalysts for overall water splitting. Notably, Mo doping could effectively modulate the electronic structure of NiCoP, leading to the increased electroactive site and improved intrinsic activity of each site. Furthermore, an electrochemical activation strategy is proposed to form Mo-doped (Ni,Co)OOH to fully boost the electrocatalytic activities for oxygen evolution reaction. Benefiting from the unique freestanding structure and Mo doping, Mo-doped NiCoP and (Ni,Co)OOH show the remarkable electrochemical performances, which are competitive among current researches. In addition, an overall water splitting device assembled by both electrodes only requires a cell voltage of 1.61 V to reach a current density of 10 mA cm-2. Therefore, this work opens up new avenues for designing nonprecious bifunctional electrocatalysts by Mo doping and in situ electrochemical activation.
Project description:Designing ever more efficient and cost-effective bifunctional electrocatalysts for oxygen/hydrogen evolution reactions (OER/HER) is greatly vital and challenging. Here, a new type of binder-free hollow TiO2@Co9S8 core-branch arrays is developed as highly active OER and HER electrocatalysts for stable overall water splitting. Hollow core-branch arrays of TiO2@Co9S8 are readily realized by the rational combination of crosslinked Co9S8 nanoflakes on TiO2 core via a facile and powerful sulfurization strategy. Arising from larger active surface area, richer/shorter transfer channels for ions/electrons, and reinforced structural stability, the as-obtained TiO2@Co9S8 core-branch arrays show noticeable exceptional electrocatalytic performance, with low overpotentials of 240 and 139 mV at 10 mA cm-2 as well as low Tafel slopes of 55 and 65 mV Dec-1 for OER and HER in alkaline medium, respectively. Impressively, the electrolysis cell based on the TiO2@Co9S8 arrays as both cathode and anode exhibits a remarkably low water splitting voltage of 1.56 V at 10 mA cm-2 and long-term durability with no decay after 10 d. The versatile fabrication protocol and smart branch-core design provide a new way to construct other advanced metal sulfides for energy conversion and storage.
Project description:The construction of heterojunction has been widely accepted as a prospective strategy for the exploration of non-precious metal-based catalysts that possess high-performance to achieve electrochemical water splitting. Herein, we design and prepare a metal-organic framework derived N, P-doped-carbon-encapsulated Ni2P/FeP nanorod with heterojunction (Ni2P/FeP@NPC) for accelerating the water splitting and working stably at industrially relevant high current densities. Electrochemical results confirmed that Ni2P/FeP@NPC could both accelerate the hydrogen and oxygen evolution reactions. It could substantially expedite the overall water splitting (1.94 V for 100 mA cm-2) which is close to the performance of RuO2 and the Pt/C couple (1.92 V for 100 mA cm-2). In particular, the durability test exhibited that Ni2P/FeP@NPC delivers 500 mA cm-2 without decay after 200 h, demonstrating the great potential for large-scale applications. Furthermore, the density functional theory simulations demonstrated that the heterojunction interface could give rise to the redistribution of electrons, which could not only optimize the adsorption energy of H-containing intermediates to achieve the optimal ΔGH* in a hydrogen evolution reaction, but also reduce the ΔG value in the rate-determining step of an oxygen evolution reaction, thus improving the HER/OER performance.
Project description:Precisely regulating of the surface structure of crystalline materials to improve their catalytic activity for lithium polysulfides is urgently needed for high-performance lithium-sulfur (Li-S) batteries. Herein, high-index faceted iron oxide (Fe2O3) nanocrystals anchored on reduced graphene oxide are developed as highly efficient bifunctional electrocatalysts, effectively improving the electrochemical performance of Li-S batteries. The theoretical and experimental results all indicate that high-index Fe2O3 crystal facets with abundant unsaturated coordinated Fe sites not only have strong adsorption capacity to anchor polysulfides but also have high catalytic activity to facilitate the redox transformation of polysulfides and reduce the decomposition energy barrier of Li2S. The Li-S batteries with these bifunctional electrocatalysts exhibit high initial capacity of 1521 mAh g-1 at 0.1 C and excellent cycling performance with a low capacity fading of 0.025% per cycle during 1600 cycles at 2 C. Even with a high sulfur loading of 9.41 mg cm-2, a remarkable areal capacity of 7.61 mAh cm-2 was maintained after 85 cycles. This work provides a new strategy to improve the catalytic activity of nanocrystals through the crystal facet engineering, deepening the comprehending of facet-dependent activity of catalysts in Li-S chemistry, affording a novel perspective for the design of advanced sulfur electrodes.
Project description:A facile in situ partial surface-oxidation strategy to integrate CoO domains with CoSe2 nanobelts on Ti mesh (denoted as CoO/CoSe2) via direct calcination of CoSe2-diethylenetriamine precursors is reported. The resulted self-supported CoO/CoSe2 exhibits an outstanding activity and stability in neutral media toward both hydrogen evolution reaction and oxygen evolution reaction.
Project description:Earth-abundant and efficient bifunctional electrocatalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are highly significant for renewable energy systems. However, the performance of existing electrocatalysts is usually restricted by the low electroic conductivity and the limited amount of exposed active sites. In this work, (Fe0.2Ni0.8)0.96S tubular spheres supported on Ni foam have been prepared by a sulfuration of FeNi layered double hydroxide spheres grown on Ni foam. Benefiting from the unique tubular sphere architecture, the rich inner defects and the enhanced electron interactions between Fe, Ni and S, this electrocatalyst shows low overpotential of 48 mV for HER at 10 mA cm-2 in 1.0 mol L-1 KOH solution, which is one of the lowest value of non-previous electrocatalyts for HER in alkaline electrolyte. Furthermore, assembled this versatile electrode as an alkaline electrolyzer for overall water splitting, a current density of 10 mA cm-2 is achieved at a low cell voltage of 1.56 V, and reach up to 30 mA cm-2 only at an operating cell voltage of 1.65 V.
Project description:The facile synthesis of highly active and stable bifunctional electrocatalysts to catalyze water splitting is attractive but challenging. Herein, we report the electrodeposition of Pt-decorated Ni(OH)2/CeO2 (PNC) hybrid as an efficient and robust bifunctional electrocatalyst. The graphite-supported PNC catalyst delivers superior hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activities over the benchmark Pt/C and RuO2, respectively. For overall water electrolysis, the PNC hybrid only requires a cell voltage of 1.45 V at 10 mA cm-2 and sustains over 85 h at 1000 mA cm-2. The remarkable HER/OER performances are attributed to the superhydrophilicity and multiple effects of PNC, in which Ni(OH)2 and CeO2 accelerate HER on Pt due to promoted water dissociation and strong electronic interaction, while the electron-pulling Ce cations facilitate the generation of high-valence Ni OER-active species. These results suggest the promising application of PNC for H2 production from water electrolysis.