Moreover, this work demonstrates a defect-driven thermocatalytic system based on SnSe nanospheres that efficiently produces H₂O₂ from H₂O and O₂ at remarkably low temperatures (40°C), without requiring additional energy input or chemical additives. The SnSe nanosheet catalyst with Sn vacancies achieves a high H₂O₂ production rate of 2.6 mmol g^-1 h^-1 at 40°C and exhibits excellent stability,  maintaining consistent performance for over 50 hours in a flow reactor. Notably, most such defect-rich materials (including SnSe) possess excellent thermoelectric properties. This dual functionality suggests a promising strategy for developing hybrid low-temperature thermoelectric-catalytic systems, where low-grade waste heat could be effectively harvested through thermoelectric effects to further reduce the overall energy consumption of the catalytic process. In contrast, current water electrolysis systems typically operate with hot water (80–90 °C), noble metal Pt-based catalysts, and exhibit high electrical energy consumption. By integrating thermoelectric catalysis with low-cost thermoelectric materials as catalysts, significant energy savings can be achieved—a prospect that underscores both technological attractiveness and the need for further research.