Overpotential

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

Tuning the Activity of Carbon for Electrocatalytic Hydrogen Evolution via an Iridium-Cobalt Alloy Core Encapsulated in Nitrogen-Doped Carbon Cages.

Abstract: Graphene, a 2D material consisting of a single layer of sp2 -hybridized carbon, exhibits inert activity as an electrocatalyst, while the incorporation of heteroatoms (such as N) into the framework can tune its electronic properties. Because of the different electronegativity between N and C atoms, electrons will transfer from C to N in N-doped graphene nanosheets, changing inert C atoms adjacent to the N-dopants into active sites. Notwithstanding the achieved progress, its intrinsic activity in acidic media is still far from Pt/C. Here, a facile annealing strategy is adopted for Ir-doped metal-organic frameworks to synthesize IrCo nanoalloys encapsulated in N-doped graphene layers. The highly active electrocatalyst, with remarkably reduced Ir loading (1.56 wt%), achieves an ultralow Tafel slope of 23 mV dec-1 and an overpotential of only 24 mV at a current density of 10 mA cm-2 in 0.5 m sulfuric acid solution. Such superior performance is even superior to the noble-metal catalyst Pt. Surface structural and computational studies reveal that the superior behavior originates from the decreased ΔGH* for HER induced by the electrons transferred from the alloy core to the graphene layers, which is beneficial for enhancing CH binding.

Fast site-to-site electron transfer of high-entropy alloy nanocatalyst driving redox electrocatalysis

Abstract: Designing electrocatalysts with high-performance for both reduction and oxidation reactions faces severe challenges. Here, the uniform and ultrasmall (~3.4 nm) high-entropy alloys (HEAs) Pt18Ni26Fe15Co14Cu27 nanoparticles are synthesized by a simple low-temperature oil phase strategy at atmospheric pressure. The Pt18Ni26Fe15Co14Cu27/C catalyst exhibits excellent electrocatalytic performance for hydrogen evolution reaction (HER) and methanol oxidation reaction (MOR). The catalyst shows ultrasmall overpotential of 11 mV at the current density of 10 mA cm−2, excellent activity (10.96 A mg−1Pt at −0.07 V vs. reversible hydrogen electrode) and stability in the alkaline medium. Furthermore, it is also the efficient catalyst (15.04 A mg−1Pt) ever reported for MOR in alkaline solution. Periodic DFT calculations confirm the multi-active sites for both HER and MOR on the HEA surface as the key factor for both proton and intermediate transformation. Meanwhile, the construction of HEA surfaces supplies the fast site-to-site electron transfer for both reduction and oxidation processes. The design of nanostructured catalysts plays a key role in the electrocatalytic redox reaction performances. Here, authors prepared uniform and small-sized high-entropy alloy PtNiFeCoCu nanoparticles that showed improved activities for H2 evolution methanol oxidation reactions.

Pt Single Atoms Supported on N-Doped Mesoporous Hollow Carbon Spheres with Enhanced Electrocatalytic H 2 -Evolution Activity

Abstract: The electronic metal-support interaction (EMSI) plays a crucial role in catalysis as it can induce electron transfer between metal and support, modulate the electronic state of the supported metal, and optimize the reduction of intermediate species In this work, the tailoring of electronic structure of Pt single atoms supported on N-doped mesoporous hollow carbon spheres (Pt1 /NMHCS) via strong EMSI engineering is reported The Pt1 /NMHCS composite is much more active and stable than the nanoparticle (PtNP ) counterpart and commercial 20 wt% Pt/C for catalyzing the electrocatalytic hydrogen evolution reaction (HER), exhibiting a low overpotential of 40 mV at a current density of 10 mA cm-2 , a high mass activity of 207 A mg-1 Pt at 50 mV overpotential, a large turnover frequency of 2018 s-1 at 300 mV overpotential, and outstanding durability in acidic electrolyte Detailed spectroscopic characterizations and theoretical simulations reveal that the strong EMSI effect in a unique N1 -Pt1 -C2 coordination structure significantly tailors the electronic structure of Pt 5d states, resulting in promoted reduction of adsorbed proton, facilitated H-H coupling, and thus Pt-like HER activity This work provides a constructive route for precisely designing single-Pt-atom-based robust electrocatalysts with high HER activity and durability

Boron Nitride Nanosheet on Gold as an Electrocatalyst for Oxygen Reduction Reaction: Theoretical Suggestion and Experimental Proof

Abstract: Boron nitride (BN), which is an insulator with a wide band gap, supported on Au is theoretically suggested and experimentally proved to act as an electrocatalyst for oxygen reduction reaction (ORR). Density-functional theory calculations show that the band gap of a free h-BN monolayer is 4.6 eV but a slight protrusion of the unoccupied BN states toward the Fermi level is observed if BN is supported on Au(111) due to the BN–Au interaction. A theoretically predicted metastable configuration of O2 on h-BN/Au(111), which can serve as precursors for ORR, and free energy diagrams for ORR on h-BN/Au(111) via two- and four-electron pathways show that ORR to H2O2 is possible at this electrode. It is experimentally proved that overpotential for ORR at the gold electrode is significantly reduced by depositing BN nanosheets. No such effect is observed at the glassy carbon electrode, demonstrating the importance of BN–substrate interaction for h-BN to act as the ORR electrocatalyst. A possible role of the edge of the ...