Tip‐Enhanced Electric Field: A New Mechanism Promoting Mass Transfer in Oxygen Evolution Reactions

Abstract

The slow kinetics of oxygen evolution reaction (OER) causes high power consumption for electrochemical water splitting. Various strategies have been attempted to accelerate the OER rate, but there are few studies on regulating the transport of reactants especially under large current densities when the mass transfer factor dominates the evolution reactions. Herein, NixFe1–x alloy nanocones arrays (with ≈2 nm surface NiO/NiFe(OH)2 layer) are adopted to boost the transport of reactants. Finite element analysis suggests that the high‐curvature tips can enhance the local electric field, which induces an order of magnitude higher concentration of hydroxide ions (OH−) at the active sites and promotes intrinsic OER activity by 67% at 1.5 V. Experimental results show that a fabricated NiFe nanocone array electrode, with optimized alloy composition, has a small overpotential of 190 mV at 10 mA cm−2 and 255 mV at 500 mA cm−2. When calibrated by electrochemical surface area, the nanocones electrode outperforms the state‐of‐the‐art OER electrocatalysts. The positive effect of the tip‐enhanced local electric field in promoting mass transfer is also confirmed by comparing samples with different tip curvature radii. It is suggested that this local field enhanced OER kinetics is a generic effect to other OER catalysts.

Highly Curved Nanostructure‐Coated Co, N‐Doped Carbon Materials for Oxygen Electrocatalysis

“…Precious metal based catalysts (such as Pt/C and RuO 2 ) are expensive, while low‐cost transition‐metal‐based catalysts still does not meet commercial requirements [11–17] . Recently, materials with highly curved surface have been applied in energy‐related small molecule activation reactions due to the tensile strain effect and local electric field enhancement [18–23] . For example, Guo et al.…”

“…[11][12][13][14][15][16][17] Recently, materials with highly curved surface have been applied in energy-related small molecule activation reactions due to the tensile strain effect and local electric field enhancement. [18][19][20][21][22][23] For example, Guo et al designed a highly curved PdMo bimetallene material, which exhibits excellent bifunctional ORR/OER performance. [24] Dai et al designed a C 60 -adsorbed carbon nanotube hybrid material, where C 60 acted as an electronacceptor to promote interfacial charge transfer, resulting in high-performance in ORR/OER.…”

Electrocatalytic Hydrogen Evolution Reaction Related to Nanochannel Materials

“…For example, for vertically aligned nanoneedles or nanowire arrays, which seem opposite to the traditional channel materials, the irregular space between the nanoneedles or nanowires makes them other kinds of channel materials. [15] Moreover, in view of that the host material could be either active or inactive, the different configurations of electrocatalysts confined in inactive host porous materials, electrocatalysts directly work as host materials, electrocatalysts confined in active host materials are discussed for different channel materials. Finally, some scientific challenges that would arise during the development of the channel materials as HER electrocatalysts are pointed out and an outlook for the following researches is also provided.…”

Cobalt–Iron–Phosphate Hydrogen Evolution Reaction Electrocatalyst for Solar-Driven Alkaline Seawater Electrolyzer

“…Particularly, the shape of the nanoneedles could extensively increase the concentrations of the reactants in the active sites and enhance local electric fields that promote the intrinsic catalytic activity. [50] Therefore, the shape of (Co,Fe)PO4 is suitable for electrochemical water splitting. , respectively.…”