Soft-template synthesis of oxygen vacancy-rich mesoporous SnO2 for efficient CO2 electroreduction to formate

Materials with ordered mesopores are attracting considerable interest due to their extraordinary efficacy in energy storage and conversion systems, particularly in electrocatalysis, which can be attributed to their extensive surface areas and adjustable porosity. Here, we present a rational design and synthesis of a novel ordered mesoporous SnO 2 (OMS-SnO 2 ) electrocatalyst utilizing the soft-template sol-gel method using Pluronic F127 as a structure-directing agent and trimethylbenzene (TMB) as a chelating agent. The OMS-SnO 2 produced has a remarkably high surface area of 230.84 m 2 /g, with uniform mesopores averaging 4.17 nm and a significant density of oxygen vacancies. Using a gas-fed flow cell setup, OMS-SnO 2 shows exceptional selectivity for formate synthesis and electrocatalytic activity. With an applied potential of -1.2 V vs. RHE, the catalyst exhibits outstanding intrinsic activity, achieving a high partial current density of -119.40 mA cm -3 for formate. Moreover, at – 0.8 V vs. RHE, it achieves an impressive Faradaic efficiency (FE) of 91.66% for formate, indicating highly selective two-electron reduction of CO 2 . The system achieves a rate of formate of 1392.71 mg L -1 h 1 , among the highest reported under similar reaction conditions, while maintaining a high cathodic energy efficiency (CEE) of 64.57% and TOF (∼1600 h -1 ). These results underscore the crucial role of mesoporosity and defect engineering in boosting CO 2 electroreduction performance. A novel ordered mesoporous SnO 2 (OMS-SnO 2 ) electrocatalyst, synthesized via a soft-template sol-gel approach, exhibits a high surface area (230.84 m 2 /g) and uniform pore size (∼4.17 nm), enabling excellent activity and stability for CO 2 electroreduction. At –0.8 V vs RHE, OMS-SnO 2 achieves a Faradaic efficiency of 91.66% for formate production, with sustained operation over 40 hours, highlighting the synergy of mesoporosity and defect engineering in enhancing electrocatalytic performance. • Ordered mesoporous SnO 2 (230.84 m 2 /g, 4.17 nm pores) synthesized via sol–gel method. • Oxygen vacancies boost CO 2 adsorption and intrinsic electrocatalytic activity. • High formate selectivity: 91.66% FE at −0.8 V and high partial current density of −119.40 mA cm -3 at −1.2 V vs. RHE. • High formate rate: 1392.71 mg L -1 h -1 with 64.57% cathodic energy efficiency (CEE).