Yin, HangSun, ZhehaoLiu, KailiLi, ZhuofengWibowo, Ary AnggaraChen, JiayiGu, HuiminJing, XuechenChen, Yi-LunMacdonald, DanielJia, GuohuaHadar, IdoYin, Zongyou2025-06-302025-06-302050-7488WOS:001433702900001ORCID:/0000-0002-5631-4872/work/182749328ORCID:/0000-0001-5792-7630/work/182749688https://www.webofscience.com/api/gateway?GWVersion=2&SrcApp=anu_research_portal_plus2&SrcAuth=WosAPI&KeyUT=WOS:001433702900001&DestLinkType=FullRecord&DestApp=WOS_CPLhttps://hdl.handle.net/1885/733765994Syngas, 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 ∼ 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 ∼3300 μmol 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.The authors acknowledge the financial support from the Australian Research Council (FT230100059, DP240100687, IH220100012, LP210100436), and the support from the Australian Microscopy and Microanalysis Research Facility at the Centre for Advanced Microscopy, the Australian National University. This research was undertaken with the assistance of resources provided by the National Computational Infrastructure (NCI) facilities at the Australian National University, which were allocated through the National Computational Merit Allocation Scheme (NCMAS) and ANU Merit Allocation Scheme (ANUMAS).8enPublisher Copyright: © 2025 The Royal Society of Chemistry.Total-energy calculationsReductionCatalystsCo3o42025-02-2110.1039/d4ta08991j105001578750