Overpotential

About: Overpotential is a research topic. Over the lifetime, 16474 publications have been published within this topic receiving 616632 citations.

Hierarchical CoP/Ni5P4/CoP microsheet arrays as a robust pH-universal electrocatalyst for efficient hydrogen generation

Abstract: Highly active catalysts composed of earth-abundant materials, performing as efficiently as Pt catalysts, are crucial for sustainable hydrogen production through water splitting. However, most efficient catalysts consist of nanostructures made via complex synthetic methods, making scale-up quite challenging. Here we report an effective strategy for developing a very active and durable pH-universal electrocatalyst for the hydrogen evolution reaction (HER). This catalyst is constructed using a sandwich-like structure, where hierarchical cobalt phosphide (CoP) nanoparticles serve as thin skins covering both sides of nickel phosphide (Ni5P4) nanosheet arrays, forming self-supported sandwich-like CoP/Ni5P4/CoP microsheet arrays with lots of mesopores and macropores. The as-prepared electrocatalyst requires an overpotential of only 33 mV to achieve a benchmark of 10 mA cm−2, with a very large exchange current density and high turnover frequencies (TOFs) in acid media, superior to most electrocatalysts made of metal phosphides, well-known MoS2 and WS2 catalysts, and it performs comparably to state-of-the-art Pt catalysts. In particular, this electrocatalyst shows impressive operational stability at an extremely large current density of 1 A cm−2, indicating its possible application toward large-scale water electrolysis. Additionally, this electrocatalyst is very active in alkaline electrolyte (71 mV at 10 mA cm−2), which demonstrates its pH universality as a HER catalyst with outstanding catalytic activity. This simple strategy does not involve any solvothermal and hydrothermal processes, paving a new avenue toward the design of robust non-noble electrocatalysts for hydrogen production, aimed at commercial water electrolysis.

Hexagonal-Phase Cobalt Monophosphosulfide for Highly Efficient Overall Water Splitting.

Abstract: The rational design and synthesis of nonprecious, efficient, and stable electrocatalysts to replace precious noble metals are crucial to the future of hydrogen economy. Herein, a partial sulfurization/phosphorization strategy is proposed to synthesize a nonstoichiometric pyrrhotite-type cobalt monophosphosulfide material (Co0.9S0.58P0.42) with a hexagonal close-packed phase for electrocatalytic water splitting. By regulating the degree of sulfurization, the P/S atomic ratio in the cobalt monophosphosulfide can be tuned to activate the Co3+/Co2+ couples. The synergy between the nonstoichiometric nature and the tunable P/S ratio results in the strengthened Co3+/Co2+ couples and tunable electronic structure and thus efficiently promotes the oxygen/hydrogen evolution reaction (OER/HER) processes toward overall water splitting. Especially for OER, the Co0.9S0.58P0.42 material, featured with a uniform yolk–shell spherical morphology, shows a low overpotential of 266 mV at 10 mA cm–2 (η10) with a low Tafel slope...

Bifunctional Electrocatalysts for Overall Water Splitting from an Iron/Nickel-Based Bimetallic Metal-Organic Framework/Dicyandiamide Composite.

Abstract: Pyrolysis of a bimetallic metal-organic framework (MIL-88-Fe/Ni)-dicyandiamide composite yield a Fe and Ni containing carbonaceous material, which is an efficient bifunctional electrocatalyst for overall water splitting. FeNi3 and NiFe2 O4 are found as metallic and metal oxide compounds closely embedded in an N-doped carbon-carbon nanotube matrix. This hybrid catalyst (Fe-Ni@NC-CNTs) significantly promotes the charge transfer efficiency and restrains the corrosion of the metallic catalysts, which is shown in a high OER and HER activity with an overpotential of 274 and 202 mV, respectively at 10 mA cm-2 in alkaline solution. When this bifunctional catalyst was further used for H2 and O2 production in an electrochemical water-splitting unit, it can operate in ambient conditions with a competitive gas production rate of 1.15 and 0.57 μL s-1 for hydrogen and oxygen, respectively, showing its potential for practical applications.

Introducing Fe 2+ into Nickel–Iron Layered Double Hydroxide: Local Structure Modulated Water Oxidation Activity

Abstract: Exploring materials with regulated local structures and understanding how the atomic motifs govern the reactivity and durability of catalysts are a critical challenge for designing advanced catalysts. Herein we report the tuning of the local atomic structure of nickel-iron layered double hydroxides (NiFe-LDHs) by partially substituting Ni2+ with Fe2+ to introduce Fe-O-Fe moieties. These Fe2+ -containing NiFe-LDHs exhibit enhanced oxygen evolution reaction (OER) activity with an ultralow overpotential of 195 mV at the current density of 10 mA cm-2 , which is among the best OER catalytic performance to date. In-situ X-ray absorption, Raman, and electrochemical analysis jointly reveal that the Fe-O-Fe motifs could stabilize high-valent metal sites at low overpotentials, thereby enhancing the OER activity. These results reveal the importance of tuning the local atomic structure for designing high efficiency electrocatalysts.