Incorporation of silver recovery with electricity generation through methanol-Ag⁺ coupled redox fuel cell

The recovery of noble metal ions from wastewater without energy consumption is of utmost importance. Herein, a methanol-Ag⁺ coupled redox fuel cell (CRFC) was developed to realize silver removal and electricity generation simultaneously. In this system with alkaline methanol as fuel on the anode, Ag⁺ in catholyte was reduced. The highest open circuit voltage of 1.28 V and maximum power density of 17.4 W·m⁻² were achieved at 0.1 mol·L⁻¹ Ag⁺ (pH=1.1). More than 90% Ag⁺ can be removed in 6 h, and over 60% of cathodic efficiency was achieved simultaneously when using Ag⁺ as electron acceptors. Morphology analysis showed that dendritic Ag particles were loosely deposited on the cathode after 2 h operation. The size of the silver dendrites increased with Ag⁺ concentration increase. Eventually, a fed-batch mode was conducted to confirm that either the Ag⁺ is efficiently reduced or the energy in chemicals has been sustainably retrieved in electricity.