Integrated electrochemical system using tin-phthalocyanine/graphene nanocomposite for synergistic formate production and rapid seawater desalination.

Escalating carbon dioxide (CO2) emissions and widespread freshwater scarcity represent critical challenges to global environmental sustainability. This study addresses both issues simultaneously by coupling electrochemical CO2 reduction (CO2RR) with seawater desalination using a novel N-SnPc/NRGO nanocomposite. This material was fabricated by anchoring tin-phthalocyanine nanostructures (N-SnPc) onto nitrogen-doped reduced graphene oxide (NRGO). The unique architecture enhances electrical conductivity and increases the exposure of active sites, optimizing electron transfer and reactant mass transport, thereby boosting CO2RR performance towards formate production. The optimized N-SnPc/NRGO composite (1:2 mass ratio) achieved a high formate Faradaic efficiency (FEformate) of 86.0 % at -0.84 V vs. reversible hydrogen electrode (RHE), alongside excellent long-term operational stability. Density functional theory (DFT) calculations revealed that NRGO modification enhances the conductivity of SnPc and modulates the p-band center of the SnN4 sites, promoting CO2 adsorption and rationalizing the elevated CO2RR activity. Furthermore, when integrated into an electrochemical desalination device, the N-SnPc/NRGO (1:2) cathode facilitated a rapid salt removal rate (SRR) of 778 μg cm-2 min-1 while maintaining an 83.3 % FEformate. Processing natural seawater, the device achieved freshwater standard with a total salt removal efficiency of 99.7 %. This work introduces a promising strategy for designing cost-effective, high-performance Sn-based CO2RR electrocatalysts and presents an innovative approach to tackling water resource challenges through integrated electrochemical systems.