A silver wire aerogel promotes hydrogen peroxide reduction for fuel cells and electrochemical sensors

The H₂O₂ reduction reaction (H₂O₂RR) has emerged as an instrumental process in fuel cells and H₂O₂ sensors. The practicability of the H₂O₂RR, however, is largely hindered by its sluggish electron transfer kinetics and poor H₂O₂ mass transport efficiency. Herein, a three-dimensional monolithic silver wire aerogel without any conductive supports is prepared and demonstrated to be a promising H₂O₂RR catalyst. The interconnected, continuous Ag wires and the substrate-free feature allow rapid electron transport within and transfer from Ag wires. The sub-micron voids in the aerogel facilitate H₂O₂ mass transport. Thanks to these merits, a H₂O₂-fed fuel cell with the Ag-aerogel cathode delivers a maximal areal power density of 299.3 ± 33.7 W m^-2. This value is >1000 times and ∼10 times higher than that of the fuel cells with quasi-one-dimensional Ag rod and quasi-two-dimensional Ag wire-coated carbon fiber cathodes, respectively. Additionally, the Ag Wire-gel functions as a sensing platform in a microfluidic H₂O₂ sensor chip and displays high sensitivity, a small limit of detection and a rapid response time. The concept of building three-dimensional metal wire aerogels demonstrated in this work is expected to provide avenues for the design and synthesis of other metal-wire aerogel catalysts to significantly advance the performance of electrochemical devices involving the H₂O₂RR.