Tube‐Sponge‐Inspired Hierarchical Electrocatalysts with Boosted Mass and Electron Transfer for Efficient Oxygen Evolution

Abstract

Water splitting involves a hydrogen evolution reaction (HER) at the cathode and an oxygen evolution reaction (OER) at the anode, and OER has been considered as the major bottleneck for water splitting due to the sluggish reaction kinetics and high OO bond formation energy barrier caused by its four-electron coupling process. [2][3][4][5] Designing the external-and internal structure of electrocatalysts is fundamental to achieve high catalytic activities at low overpotential and equally important to the electrocatalysts themselves, the reaction efficiency also strongly depends on the mass transfer outside the electrode surface and electron transfer inside the electrode structure. [4][5][6] The mass transfer at the interfaces between the catalyst and electrolyte is responsible for the immediate supplying of electrolytes (and reactants) and associated with rapid release of bubbles generated by the reactions (O 2 gas, for the case of OER). [7] The kinetics of mass transfer as the rate-controlling step, therefore, govern the efficiency of the electrochemical reaction, by taking much larger time constant compared with that of the electron transfer. [8,9] For gas-evolving electrochemical system, bubbles may adhere to the catalyst's surface and block the active sites by forming bubble froth layers. This process

Critical challenges and opportunities for the commercialization of alkaline electrolysis: high current density, stability, and safety

“…6g). 104 NiFe-P Zn in situ grown on the PNTA surface, not only enlarge the surface area but also facilitates electron transfer from the catalyst to the conductive support (Fig. 6h).…”

“…(k) Polarization curves of NiFe-P Zn @PNTA and NiFe-P Zn @NTA. Reproduced with permission 104. Copyright 2020, Wiley.…”

Bubble Engineering on Micro-/Nanostructured Electrodes for Water Splitting

“…The principles evidenced by the above experiments can be used to illustrate the reason why biomimetic hierarchical electrodes have better performance for water splitting. Recently, more and more biomimetic hierarchical electrodes have been developed for water splitting. , For instance, the porous nickel tube arrays (PNTA) electrodes mimicking the deep-sea sponges were proposed for OER (Figure e,f) . On the one hand, the as-formed bubbles in the superaerophobic PNTA electrode can be timely released, and the bubbles collide with one another to accelerate their movement during the rising process.…”

Electron Regulation of Heterostructured Pt/Rh Metallene Boosts Ethylene Glycol Electrooxidation and Hydrogen Evolution

“…Hydrogen has received widespread attention as a new renewable energy to substitute fossil fuel owing to its high energy density and low environmental pollution. − Among many methods for producing hydrogen, water electrolysis (2H 2 O → 2H 2 + O 2 ) is a feasible and efficient approach using renewable electronic energy, involving the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). − Unfortunately, it consumes an enormous amount of energy owing to the sluggish kinetics of anodic OER. , Recently, the substitution of OER with thermodynamically more favorable oxidation reactions of small molecules (e.g., ethanol, , primary amines, urea, formate, and glucose) is an emerging strategy for producing hydrogen efficiently. Moreover, anodic oxidation can produce other high-value-added chemicals, which is favorable for practical applications.…”