Overpotential

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

High‐Entropy Metal Sulfide Nanoparticles Promise High‐Performance Oxygen Evolution Reaction

Abstract: Transition metal sulfides with a multi‐elemental nature represent a class of promising catalysts for oxygen evolution reaction (OER) owing to their good catalytic activity. However, their synthesis remains a challenge due to the thermodynamic immiscibility of the constituent multimetallic elements in a sulfide structure. Herein, for the first time the synthesis of high‐entropy metal sulfide (HEMS, i.e., (CrMnFeCoNi)Sx) solid solution nanoparticles is reported. Computational and X‐ray photoelectron spectroscopy analysis suggest that the (CrMnFeCoNi)Sx exhibits a synergistic effect among metal atoms that leads to desired electronic states to enhance OER activity. The (CrMnFeCoNi)Sx nanoparticles show one of the best activities (low overpotential 295 mV at 100 mA cm−2 in 1 m KOH solution) and good durability (only slight polarization after 10 h by chronopotentiometry) compared with their unary, binary, ternary, and quaternary sulfide counterparts. This work opens up a new synthesis paradigm for high‐entropy compound nanoparticles for highly efficient electrocatalysis applications.

Metal-Organic Framework-Derived Hierarchical (Co,Ni)Se2@NiFe LDH Hollow Nanocages for Enhanced Oxygen Evolution.

Abstract: High-efficient electrocatalysts are crucial for fuel cell applications; however, the whole cell performance is generally restricted by the anodic part because of the sluggish kinetics involved in the oxygen evolution reaction (OER) process. Herein, a hierarchical hollow (Co,Ni)Se2@NiFe layered double hydroxide (LDH) nanocage was synthesized by deriving from the metal–organic framework (MOF) of ZIF-67. Concretely, it involves first fabrication of hollow rhombic (Co,Ni)Se2 nanocages and then deposition of NiFe LDH nanosheets on the surface of nanocages. Notably, the incorporation of Ni into Co-based ZIF-67 (via ion-exchange) could tail the atomic arrangement of the MOF, exposing more additional active sites in the following selenization treatment. The as-synthesized (Co,Ni)Se2@NiFe LDH demonstrates splendid OER performance with a small overpotential of 277 mV (to launch a current density of 10 mA cm–2), a small Tafel slope of 75 mV dec–1, and robust durability (a slight stability decay of 5.1% after 17 h of...

Ultrafine Pt Nanoparticle-Decorated Co(OH)2 Nanosheet Arrays with Enhanced Catalytic Activity toward Hydrogen Evolution

Abstract: The combinations of Earth-abundant materials with noble metals provide an orientation for developing highly active and stable catalysts toward hydrogen production with reduced noble metal loadings. Here, we designed carbon cloth (CC)-supported Earth-abundant Co(OH)2 nanosheets array (Co(OH)2/CC) as an ideal three-dimensional (3D) substrate for Pt electrodeposition (Pt–Co(OH)2/CC, Pt in Pt–Co(OH)2: 5.7 wt %) to achieve top performance of a hydrogen evolution reaction (HER) under alkaline and neutral conditions. The Pt–Co(OH)2/CC catalyst exhibits a near-zero onset overpotential and a Tafel slope of 70 mV dec–1, and it requires an overpotential of 32, 54, and 122 mV to deliver the geometrical current density of 10, 20, and 100 mA cm–2, respectively, with catalytic activities exceeding to those of the commercial Pt/C decorated CC (Pt/C/CC). Furthermore, the HER activity of Co(OH)2 decorated with several transition metals (Ni, Co, and Fe) was demonstrated in experiments, further validating the high HER activi...

Electrocatalytic oxidation of glycerol on Pt/C in anion-exchange membrane fuel cell: Cogeneration of electricity and valuable chemicals

Abstract: Electrocatalytic oxidation of glycerol for cogenerating electricity and higher-valued chemicals on a Pt/C anode catalyst (2.4 nm) in an anion-exchange membrane fuel cell (AEMFC) was investigated. The peak power density of an anion-exchange membrane – direct glycerol fuel cell (AEM-DGFC) with 1.0 mgPt cm−2 anode and non-PGM catalyst cathode can reach 124.5 mW cm−2 at 80 °C and 58.6 mW cm−2 at 50 °C, while the highest selectivity of C3 acids (glyceric acid + tartronic acid) can reach 91%. The study found that higher pH reaction media could enhance fuel cell output power density (electricity generation) and selectivity of C3 acids, while lower glycerol concentration could improve the selectivity of deeper-oxidized products (mesoxalic acid and oxalic acid). The fuel cell reactor with the Pt/C anode catalyst demonstrated an excellent reusability, and successfully obtained tartronic acid with a selectivity of 50% and mesoxalic acid with a selectivity of 7%, which are high compared to heterogeneous catalytic glycerol oxidation in batch reactors. It is found that the anode overpotential can regulate the oxidation product distribution, and that higher anode overpotentials favor C C bond breaking, thus lowering the C3 acids selectivity. The reaction sequence of glycerol electro-oxidation detected in an electrolysis half cell with an on-line sample collection and off-line HPLC analysis agrees with the results obtained from single fuel cell tests. However, inconsistencies between the two systems still exist and are possibly due to different reaction environments, such as electrode structure, glycerol:catalyst ratio, and residence time of reactants.