Towards a broad-operation window for stable CO2 electroreduction to HCOOH by a design involving upcycling electroplating sludge-derived Sn@N/P-doped carbon

Abstract

The electrochemical CO₂ reduction reaction (CO₂RR) to HCOOH offers a promising strategy for a carbon-neutral cycle. Sn-Based materials have been demonstrated as applicable in extensive studies of CO₂RR to HCOOH, but great challenges still remain, including the weak CO₂ adsorption and narrow potential window as well as low stability. Herein, we developed ultrasmall Sn nanoparticles inlaid on N/P-doped carbon (Sn@NPC) composites by an upcycling design using Sn electroplating sludge. The obtained Sn@NPC electrode exhibited a higher Faradaic efficiency of 87.93% for HCOOH at 1.05 V vs. RHE and an FE over 80% within a 500 mV broad potential window. Moreover, the Sn@NPC electrode achieved excellent long-term stability up to 105 h, which was superior to that of most Sn-based catalysts in similar systems. Density functional theory calculations demonstrated that Sn@NPC could enhance CO₂ adsorption, which led to stronger *OCHO adsorption, weaker *HCOOH adsorption and faster electron/mass transport. This work may provide a promising lead for recycling metal from electroplating sludge and for the design of efficient and stable catalysts for the CO₂RR.