Promoting Electrocatalysis upon Aerogels

Abstract

Electrocatalysis plays a prominent role in renewable energy conversion and storage, enabling a number of sustainable processes for future technologies. There are generally three strategies to improve the efficiency (or activity) of the electrocatalysts: i) increasing the intrinsic activity of the catalyst itself, ii) improving the exposure of active sites, and iii) accelerating mass transfer during catalysis (both reactants and products). These strategies are not mutually exclusive and can ideally be addressed simultaneously, leading to the largest improvements in activity. Aerogels, as featured by large surface area, high porosity, and self‐supportability, provide a platform that matches all the aforementioned criteria for the design of efficient electrocatalysts. The field of aerogel synthesis has seen much progress in recent years, mainly thanks to the rapid development of nanotechnology. Employing precursors with different properties enables the resulting aerogel with targeted catalytic properties and improved performances. Here, the design strategies of aerogel catalysts are demonstrated, and their performance for several electrochemical reactions is reviewed. The common principles that govern electrocatalysis are further discussed for each category of reactions, thus serving as a guide to the development of future aerogel electrocatalysts.

Engineering Multimetallic Aerogels for pH‐Universal HER and ORR Electrocatalysis

“…Energy Mater. 2020, 10,1903857 (SEM) images (Figure 1b,e). With a close-up observation using transmission electron microscopy (TEM), a branched-NW structure with high crystallinity was identified at the nanoscale (Figure 1c,f).…”

“…Energy Mater. 2020, 10,1903857 as interconnected core backbones and the electrocatalytically active rhodium as the reaction sites. Therefore, the electron transfer is enhanced and the surface-bond electrocatalytic reactions are promoted.…”

“…Energy Mater. 2020, 10,1903857 bubbles from both the cathode (hydrogen evolution) and the anode (oxygen evolution) ( Figure 3e). Afterward, the stability of the water splitting device was characterized by chronopotentiometric tests over a 10 h continuous operation.…”

“…[ 8,9 ] Compared with conventional catalysts, NMAs are capable of delivering a considerably high performance surpassing not only non‐metal‐ or transition‐metal‐based catalysts, but also the commercial noble‐metal‐based catalysts such as Pt/C and Pd/C. [ 10 ] However, presumably due to the limited number of available compositions of NMAs, the studied electrocatalytic reactions are mostly centered on the alcohol oxidation, although a few reports on ORR and OER have been also presented. For example, several palladium‐based aerogels were explored for OER, displaying a current density of 1.2–11.6 times higher than that of commercial Pd‐based catalysts.…”

Back Cover: Freeze–Thaw‐Promoted Fabrication of Clean and Hierarchically Structured Noble‐Metal Aerogels for Electrocatalysis and Photoelectrocatalysis (Angew. Chem. Int. Ed. 21/2020)

“…Aerogels are al arge class of self-supported porous materials with virtually unlimited compositions ranging from silica, polymers,n anocarbons,a nd semiconductors to met-als. [1][2][3][4][5][6][7] Especially for the recently emerging noble-metal aerogels (NMAs), their combined features,i ncluding selfsupported architectures,h igh specific surface areas,3 D electron/mass transfer pathways,a nd numerous optically/ catalytically active sites,h ave endowed them with broad application prospects such as in electrocatalysis,s urfaceenhanced Raman scattering, and sensing. [8][9][10] However,since their discovery in 2009, [11] the development has been quite slow,w hich is presumably due to the great challenges encountered by the material fabrication.…”