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 approximate to 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.