Gold–Copper Aerogels with Intriguing Surface Electronic Modulation as Highly Active and Stable Electrocatalysts for Oxygen Reduction and Borohydride Oxidation

Abstract

We, for the first time, report the successful synthesis of self-assembled AuCu aerogels by a one-pot kinetically controlled approach. A startling electronic modulation effect of Cu on Au was observed across the entire alloy composition range, for which the optimal upshift of the d-band center for the highest activities was 0.24 eV. Owing to the combination of a nanoporous architecture and a robust electronic effect, the Au Cu aerogels exhibited better catalytic performance for the oxygen reduction reaction (ORR) and the direct borohydride oxidation reaction (BOR) than commercial Pt/C catalysts. The specific and mass ORR activities were 4.5 and 6.3 times higher, respectively, on the Au Cu aerogels than on Pt/C with negligible activity decay even after 10 000 cycles and a duration of 40 000 s. For the BOR, the Au Cu aerogels also exhibited far better selectivity and activity than Pt/C. The new AuCu aerogels show great potential as a promising alternative for Pt-based catalysts in fuel cells.

Engineering Self‐Supported Noble Metal Foams Toward Electrocatalysis and Beyond

“…[79] Because of the extreme simplicity, this method has been widely adopted and extended to Au-Cu, Pd-Cu, and Pt-Ni systems. [80][81][82] To reduce the long gelation time required for the one-step method, Lin's group addressed this issue in M-Cu (M = Pd, Pt, and Au) and Au-Pt systems by raising the reaction temperature ( Figure 7c). [74,83] Via one-pot reducing two metal salt precursors by NaBH 4 at 333 K, monolithic hydrogels formed in 2-6 h, displaying moderate SSAs of 21.3-37.5 m 2 g −1 .…”

“…The same authors found that high‐SSA aerogels (73 to 168 m 2 g −1 ) can be also obtained for the Pd–Pt system without the introduction of additives, but a much longer time of 3–17 d was required to acquire hydrogels . Because of the extreme simplicity, this method has been widely adopted and extended to Au–Cu, Pd–Cu, and Pt–Ni systems …”

“…h,i) Electrocatalytic NaBH 4 oxidation reaction, CV and chronoamperometric scans of Au–Cu aerogels in 0.1 m NaBH 4 + 3 m NaOH solution. Adapted with permission . Copyright 2018, Wiley‐VCH.…”

“…The remarkable activity of the Pd 20 Pt 80 aerogel was explained by its appropriate d‐band center, which best balances the free energies of O 2 adsorption and the surface coverage of intermediates. Following this work, different combinations of chemical composition, such as Pd–Ni and Au–Cu systems have been explored for the ORR, reaching slightly higher mass‐specific activity than that of Pt/C when performing both in a three‐electrode system or in membrane electrode assemblies . Impressively, an enhanced durability was frequently seen for NMAs compared to Pt/C, which could be ascribed to the elimination of corrodible carbon substrates …”

“…Adapted with permission. [81] Copyright 2018, Wiley-VCH. j,k) Electrocatalytic formic acid oxidation reaction, CV and chronoamperometric scans of Pd NPs, Pd, Ag 50 Pd 50 , and Ag 34 Au 33 Pd 33 sponges performed in 0.5 m H 2 SO 4 + 0.5 m HCOOH solution.…”