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1.
Nano Lett ; 2020 Feb 18.
Artigo em Inglês | MEDLINE | ID: mdl-32052980

RESUMO

Spin engineering provides a powerful strategy for manipulating the interaction between electrons in the d orbital and oxygen-containing adsorbates, while a little endeavor was performed to understand whether such a strategy can make a prosperous enhancement for fuel electrooxidations. Herein, we demonstrate that spin engineering of trimetallic Pd-Fe-Pt nanomeshes (NMs) can achieve superior enhancement for fuel electrooxidations. Magnetization characterizations reveal that Pd59Fe27Pt14 NMs own the highest number of polarized spins (µb = 0.85 µB/f.u.), playing an important role on facilitating the adsorption of OHads to promote the oxidation of COads, as confirmed by theoretical results. Consequently, the optimized Pd59Fe27Pt14 NMs exhibit excellent methanol oxidation reaction activity and stability with a mass activity of 1.61 A mgPt-1, 2.6-fold and 7.3-fold larger than those of PtRu/C and Pt/C. Such catalysts also present exceptional performances in ethanol oxidation and formic acid oxidation reactions. Our work highlights a new strategy for designing efficient electrocatalysts for fuel electrooxidations and beyond.

2.
Angew Chem Int Ed Engl ; 58(8): 2316-2320, 2019 Feb 18.
Artigo em Inglês | MEDLINE | ID: mdl-30609139

RESUMO

Perovskite-based electrocatalysts are one of the most promising materials for oxygen evolution reaction (OER), but their activity and durability are still far from desirable. Herein, we demonstrate that the double perovskite LaFex Ni1-x O3 (LFNO) nanorods (NRs) can be adopted as highly active and stable OER electrocatalysts. The optimized LFNO-II NRs with Ni/Fe ratio of 8:2 achieve a low overpotential of 302 mV at 10 mA cm-2 and a small Tafel slope of 50 mV dec-1 , outperforming those of the commercial Ir/C. The LFNO-II NRs also show high OER stability with slight current decrease after 20 h. The enhanced activity is explained by the improved surface area, tailored electronic structure as well as strong hybridization between O and Ni.

3.
Nat Commun ; 9(1): 4933, 2018 11 22.
Artigo em Inglês | MEDLINE | ID: mdl-30467320

RESUMO

While engineering the phase and structure of electrocatalysts could regulate the performance of many typical electrochemical processes, its importance to the carbon dioxide electroreduction has been largely unexplored. Herein, a series of phase and structure engineered copper-tin dioxide catalysts have been created and thoroughly exploited for the carbon dioxide electroreduction to correlate performance with their unique structures and phases. The copper oxide/hollow tin dioxide heterostructure catalyst exhibits promising performance, which can tune the products from carbon monoxide to formic acid at high faradaic efficiency by simply changing the electrolysis potentials from -0.7 VRHE to -1.0 VRHE. The excellent performance is attributed to the abundant copper/tin dioxide interfaces involved in the copper oxide/hollow tin dioxide heterostructure during the electrochemical process, decreasing the reaction free-energies for the formation of COOH* species. Our work reported herein emphasizes the importance of phase and structure modulating of catalysts for enhancing electrochemical CO2 reduction and beyond.

4.
ACS Nano ; 12(7): 7371-7379, 2018 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-29924585

RESUMO

The anodic oxygen evolution reaction (OER) is central to various energy conversion devices, but the investigation of the dynamic evolution of catalysts in different OER conditions remains quite limited, which is unfavorable for the understanding of the actual structure-activity relationship and catalyst optimization. Herein, we constructed monodispersed IrNi x nanoparticles (NPs) with distinct composition-segregated features and captured their structural evolution in various OER environments. We decoded the interesting self-reconstruction of IrNi x NPs during the OER, in which an Ir-skin framework is generated in an acidic electrolyte, while a Ni-rich surface layer is observed in an alkaline electrolyte owing to Ni migration. Benefiting from such self-reconstruction, considerable OER enhancements are achieved under both acidic and alkaline conditions. For comparison, IrNi x nanoframes with Ir skins prepared by chemical etching show a similar structural evolution result in the acidic electrolyte, but a total different phenomenon in the alkaline electrolyte. By tracking the structural evolution of IrNi x catalysts and correlating them with OER activity trajectories, the present work provides a significant understanding for designing efficient OER catalysts with controlled compositional distributions.

5.
ACS Nano ; 12(6): 6245-6251, 2018 Jun 26.
Artigo em Inglês | MEDLINE | ID: mdl-29763293

RESUMO

The development of electrocatalysts with high activity and stability for oxygen evolution reaction (OER) is critically important, the one being regarded as the bottleneck process of overall water splitting. Herein, we fulfill significant OER improvement in both activity and stability by constructing a class of Ni(OH)2-CeO2 supported on carbon paper (Ni xCe y@CP) with an intimate hydroxide (Ni(OH)2)-oxide (CeO2) interface. Such interface largely promotes the OER activity with a low overpotential of 220 mV at 10 mA cm-2 and a small Tafel slope of 81.9 mV dec-1 in 1 M KOH. X-ray photoelectron spectroscopy analysis shows that the intimate interface induced by the strong electronic interactions between Ni(OH)2 and CeO2 involves the modulation of binding strength between intermediates and catalysts, making a great contribution to the OER enhancement. Importantly, such intimate interface structures can be largely maintained even after a long-time stability test. We have further demonstrated that, when pairing the Ni4Ce1@CP after phosphorization (P-Ni4Ce1@CP), the Ni4Ce1@CP and P-Ni4Ce1@CP assembly is highly active and stable for overall water splitting with a low voltage of 1.68 V at 25 mA cm-2 and negligible stability delay over 30 h of continuous operation, which are much better than the commercial Ir/C and Pt/C.

6.
Small ; 13(36)2017 09.
Artigo em Inglês | MEDLINE | ID: mdl-28719034

RESUMO

Iridium (Ir) holds great promise for ethanol oxidation reaction (EOR), while its practical applications suffer from the limited shape-controlled synthesis due to its low-energy barrier for nucleation. To overcome this limitation, the preparation of a new class of ultrathin vein-like Ir-tin nanowires (IrSn NWs) with abundant oxidized Sn is reported. By tuning the ratio of Ir to Sn, the optimized Ir67 Sn33 /C exhibits the highest mass density of 95.6 mA mg-1 Ir for EOR at low potential (0.04 V), which is 4.1-fold and 20-fold higher than that of Ir/C and the commercial Pt/C, respectively. It also exhibits the smallest Tafel slope of 153 mV dec-1 and superior stability after 2 h chronoamperometric measurement. Electrochemical measurements and X-ray photoelectron spectra results confirm that the abundant oxidized Sn promotes a complete oxidization of ethanol into CO2 at low potential. This work highlights the importance of non-noble metal on enhancing the EOR performance.

7.
Small ; 13(27)2017 07.
Artigo em Inglês | MEDLINE | ID: mdl-28544112

RESUMO

The design of cost-efficient earth-abundant catalysts with superior performance for the electrochemical water splitting is highly desirable. Herein, a general strategy for fabricating superior bifunctional water splitting electrodes is reported, where cost-efficient earth-abundant ultrathin Ni-based nanosheets arrays are directly grown on nickel foam (NF). The newly created Ni-based nanosheets@NF exhibit unique features of ultrathin building block, 3D hierarchical structure, and alloy effect with the optimized Ni5 Fe layered double hydroxide@NF (Ni5 Fe LDH@NF) exhibiting low overpotentials of 210 and 133 mV toward both oxygen evolution reaction and hydrogen evolution reaction at 10 mA cm-2 in alkaline condition, respectively. More significantly, when applying as the bifunctional overall water splitting electrocatalyst, the Ni5 Fe LDH@NF shows an appealing potential of 1.59 V at 10 mA cm-2 and also superior durability at the very high current density of 50 mA cm-2 .

8.
Angew Chem Int Ed Engl ; 56(16): 4502-4506, 2017 04 10.
Artigo em Inglês | MEDLINE | ID: mdl-28322493

RESUMO

Trimetallic oxyhydroxides are one of the most effective materials for oxygen evolution reaction (OER) catalysis, a key process for water splitting. Herein, we describe a facile wet-chemical method to directly grow a series of coralloid trimetallic oxyhydroxides on arbitrary substrates such as nickel foam (NF) and carbon nanotubes (CNTs). The amount of iron in these oxyhydroxide sponges on NF and CNTs was precisely controlled, revealing that the electrocatalytic activity of the WCoFe trimetallic oxyhydroxides depends on the Fe amount in a volcano-like fashion. The optimized W0.5 Co0.4 Fe0.1 /NF catalyst exhibited an overpotential of only 310 mV to deliver a large current density of 100 mA cm-2 and a very low Tafel slope of 32 mV dec-1 . It also showed superior stability with negligible activity decay after use in the OER for 21 days (>500 h). X-ray photoelectron spectroscopy revealed that the addition of Fe leads to an on average lower Co oxidation state, which contributes to the enhanced OER performance.

9.
Nano Lett ; 16(7): 4424-30, 2016 07 13.
Artigo em Inglês | MEDLINE | ID: mdl-27249544

RESUMO

Shape-controlled noble metal nanocrystals (NCs), such as Au, Ag, Pt, Pd, Ru, and Rh are of great success due to their new and enhanced properties and applications in chemical conversion, fuel cells, and sensors, but the realization of shape control of Ir NCs for achieving enhanced electrocatalysis remains a significant challenge. Herein, we report an efficient solution method for a new class of three-dimensional (3D) Ir superstructure that consists of ultrathin Ir nanosheets as subunits. Electrochemical studies show that it delivers the excellent electrocatalytic activity toward oxygen evolution reaction (OER) in alkaline condition with an onset potential at 1.43 V versus reversible hydrogen electrode (RHE) and a very low Tafel slope of 32.7 mV decade(-1). In particular, it even shows superior performance for OER in acidic solutions with the low onset overpotential of 1.45 V versus RHE and small Tafel slope of 40.8 mV decade(-1), which are much better than those of small Ir nanoparticles (NPs). The 3D Ir superstructures also exhibit good stability under acidic condition with the potential shift of less than 20 mV after 8 h i-t test. The present work highlights the importance of tuning 3D structures of Ir NCs for enhancing OER performance.

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