Abstract Developing efficient electrocatalysts for water oxidation is of vital importance for the electrochemical production of hydrogen (H 2 ) fuels. Herein, we report the hydrothermal synthesis of a NiTe 2 nanosheet array anchored on Ti mesh (NiTe 2 /TM) through the topotactic transformation from a Ni(OH) 2 nanoarray on the basis of an anion exchange reaction. As a robust non‐noble‐metal catalyst electrode for alkaline water oxidation, NiTe 2 /TM exhibits high activity and delivers a small overpotential of 315 mV to realize an anodic geometrical current density of 10 mA cm −2 , with superior long‐term durability. It is suggested that the NiOOH species is evolved as the active phase for water oxidation. This study reveals a very profound earth‐abundant 3D catalyst electrode for electrochemical water splitting towards large‐scale and clean H 2 evolution from water.
Exploring transition metal-based, highly efficient and bifunctional catalysts for electrochemical water splitting remains a challenging task. Herein, ZnCo2S4 nanosheet array supported on nickel foam (ZnCo2S4/NF) is fabricated and demonstrated to be efficacious electrocatalyst for both oxygen evolution and hydrogen evolution reactions. The resulting catalyst affords overpotentials of only 278 mV to achieve 10 mA cm−2 towards oxygen evolution and 185 mV to reach 10 mA cm−2 towards hydrogen evolution with superior stability in alkaline solution. The assembled two-electrode water electrolyzer using ZnCo2S4/NF can reach a current density of 10 mA cm−2 by 1.66 V cell voltage.
Abstract Development of low‐cost and high‐efficiency electrocatalysts for overall water splitting is of great significance in the sustainable hydrogen economy. Herein, Fe 1.2 (CoNi) 1.8 Se x medium‐entropy metal selenides (MESes) nanoparticles are prepared via the selenylation of metal‐organic frameworks (MOFs) precursors. The optimal Fe 1.2 (CoNi) 1.8 Se 6 MESe exhibits an outstanding electrocatalytic performance in alkaline media, offering low overpotentials of 66 and 216 mV at 10 mA cm −2 for the hydrogen evolution reaction and oxygen evolution reaction, respectively. A full electrolysis apparatus with Fe 1.2 (CoNi) 1.8 Se 6 MESe as both cathode and anode displays an excellent performance, achieving 10 mA cm −2 at a potential of 1.55 V. Furthermore, density functional theory calculations demonstrate that the formation of MESe enhances the surface charge density and brings the d‐band center closer to Fermi level, as compared with that of the MOF precursor. Overall, the proposed strategy of medium‐entropy materials presents a low‐cost approach to fabricate energy storage and conversion devices.
In this Letter, we report the development of hierarchical CoTe2 nanowire array on Ti mesh (CoTe2 NA/TM) via topotactical conversion from its Co(OH)F precursor through hydrothermal tellurization reaction. As a 3D oxygen evolution electrocatalyst, such CoTe2 NA/TM exhibits excellent catalytic activity with an overpotential of 340 mV to attain 50 mA cm–2 in 1.0 M KOH. Notably, it also exhibits high durability for 25 h.
Abstract Heteroatom doping plays a significant role in optimizing the catalytic performance of electrocatalysts. However, research on heteroatom doped electrocatalysts with abundant defects and well‐defined morphology remain a great challenge. Herein, a class of defect‐engineered nitrogen‐doped Co 3 O 4 nanoparticles/nitrogen‐doped carbon framework (N‐Co 3 O 4 @NC) strongly coupled porous nanocubes, made using a zeolitic imidazolate framework‐67 via a controllable N‐doping strategy, is demonstrated for achieving remarkable oxygen evolution reaction (OER) catalysis. X‐ray photoelectron spectroscopy, X‐ray absorption fine structure, and electron spin resonance results clearly reveal the formation of a considerable amount of nitrogen dopants and oxygen vacancies in N‐Co 3 O 4 @NC. The defect engineering of N‐Co 3 O 4 @NC makes it exhibit an overpotential of only 266 mV to reach 10 mA cm −2 , a low Tafel slope of 54.9 mV dec −1 and superior catalytic stability for OER, which is comparable to that of commercial RuO 2 . Density functional theory calculations indicate N‐doping could promote catalytic activity via improving electronic conductivity, accelerating reaction kinetics, and optimizing the adsorption energy for intermediates of OER. Interestingly, N‐Co 3 O 4 @NC also shows a superior oxygen reduction reaction activity, making it a bifunctional electrocatalyst for zinc–air batteries. The zinc–air battery with the N‐Co 3 O 4 @NC cathode demonstrates superior efficiency and durability, showing the feasibility of N‐Co 3 O 4 /NC in electrochemical energy devices.
Abstract The oxygen evolution reaction (OER) on the anode side is one of the bottlenecks for electrochemical water splitting, and the search for cost‐effective and efficient catalysts for OER is highly pursued. Herein, through calcination and nitridation treatment of the Cu−Co based bimetallic metal‐organic framework precursor, nitrogen doped CuCo 2 O 4 /nitrogen‐doped carbon (N−CuCo 2 O 4 @N−C) are successfully synthesized. X‐ray photoelectron spectroscopy measurements reveal the evident change of electronic state after doping N atoms into CuCo 2 O 4 @N−C. When used as an OER electrocatalyst, N−CuCo 2 O 4 @N−C catalysts offer an overpotential of only 260 mV to reach 10 mA cm −2 , which is comparable to commercial RuO 2 catalyst. The N−CuCo 2 O 4 @N−C sample possesses a lower Tafel slope than pristine CuCo 2 O 4 @N−C sample. Moreover, a chronoamperometric study reveals that N−CuCo 2 O 4 @N−C displays excellent stability for at least 28 h. This work provides a promising heteroatom doping strategy to fabricate high‐performance OER electrocatalysts for water splitting.
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