Abstract
Synergetic management of waste activated sludge, heavy metals (HMs) and CO(2) for their valorization and cyclic utilization is rarely reported. Herein, we employed sludge-derived extracellular polymeric substances (EPS) and HMs in wastewater to fabricate a gas diffusion electrode (GDE) for electrochemical CO(2) reduction. This approach atomically dispersed Ni at each nanofiber of the GDE. Abundant N element in the EPS proved to play a key role in the formation of N(x)-Ni (mixture of N(3)-Ni and N(4)-Ni) sites for highly efficient CO(2) to CO conversion. The atomical Ni(3+) shows high catalytic activity. Direct gaseous CO(2) reduction in a membrane electrode assembly generated a current density up to 50 mA·cm(-2) with CO:H(2) ratio of ∼100 and ∼75% FE(CO) under 2.69 cell voltage. This strategy takes advantage of all waste streams generated on site and consolidates traditionally separated treatment processes to save costs, produces value-added products and generates carbon benefits during wastewater treatment.