Solar-driven dehydrogenation and dehydration of formate to syngas with near-zero CO2 emission

Syngas, a vital H2 and CO mixture, is crucial for industrial applications and advancing the circular carbon economy. Traditional photocatalytic CO2 reduction to syngas relies on sacrificial agents and photosensitizers, limiting scalability and practice. Here, we demonstrate a Co3O4-CdS heterojunction photocatalyst that efficiently converts formate (HCOO-), a stable, easily-handled and accessible CO2 reduction product, into syngas under alkaline conditions (pH similar to 10). This dual-function catalyst enables CO generation via CdS-mediated dehydration and H2 production via Co3O4-mediated dehydrogenation, achieving a syngas production rate of similar to 3300 mu mol g-1 h-1. Notably, this system operates without sacrificial agents or noble metals, with near-zero CO2 emissions, surpassing current efficiency benchmarks. By recycling CO2 into formic acid and further converting it to syngas, this approach promotes a closed carbon loop. Its cost-effectiveness, ease of formate storage, direct solar utilization, and low carbon footprint position it as a promising pathway for sustainable syngas production and clean energy solutions.