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

Escalating carbon dioxide (CO 2 ) emissions and widespread freshwater scarcity represent critical challenges to global environmental sustainability. This study addresses both issues simultaneously by coupling electrochemical CO 2 reduction (CO 2 RR) 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 CO 2 RR performance towards formate production. The optimized N-SnPc/NRGO composite (1:2 mass ratio) achieved a high formate Faradaic efficiency (FE formate ) 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 Sn N 4 sites, promoting CO 2 adsorption and rationalizing the elevated CO 2 RR 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 % FE formate . 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 CO 2 RR electrocatalysts and presents an innovative approach to tackling water resource challenges through integrated electrochemical systems.