Synergistic Dual Single-Atom Fe–Co Catalysts Anchored on Covalent Organic Framework/g-C3N4 Heterostructures for Ultrabroadband Artificial Photosynthesis via Solar CO2 Reduction and Hydrogen Evolution
Year: 2026
Type: preprint
Abstract: The efficient conversion of solar energy into chemical fuels through artificial photosynthesis represents one of the most promising approaches for mitigating global energy shortages and anthropogenic CO2 emissions. Nevertheless, simultaneously achieving highly selective CO2 photoreduction and efficient hydrogen evolution remains challenging because of sluggish reaction kinetics, limited visible-light absorption, rapid charge recombination, and insufficient active sites. Herein, we propose a novel hierarchical photocatalyst comprising atomically dispersed Fe–Co dual single atoms anchored on a covalent organic framework (COF)/g-C3N4 heterostructure (Fe–Co-SA/COF/g-C3N4). The strong electronic interaction between neighbouring Fe and Co single atoms establishes abundant asymmetric Fe–N4–Co catalytic motifs, while the crystalline COF provides highly ordered π-conjugated pathways that significantly accelerate charge transport. Simultaneously, intimate interfacial contact between the COF and g-C3N4 generates an efficient S-scheme heterojunction, promoting directional migration of photogenerated electrons and holes while preserving their strong redox potentials. Density Functional Theory (DFT) calculations reveal that the Fe–Co dual sites reduce the energy barrier for CO2 activation by approximately 45% compared with isolated Fe sites, whereas Gibbs free-energy analysis demonstrates favorable adsorption of *COOH and *H intermediates. Artificial intelligence-assisted catalyst optimization further identifies the optimal Fe/Co atomic ratio and coordination environment, enabling ultrabroadband solar harvesting extending from ultraviolet to near-infrared wavelengths (300–1800 nm). Under simulated AM 1.5G solar irradiation, the optimized Fe–Co-SA/COF/g-C3N4 photocatalyst achieves remarkable CO evolution rates exceeding 1450 μmol g-1 h-1, CH4 production of 165 μmol g-1 h-1, and H2 evolution of 12.4 mmol g-1 h-1, together with an apparent quantum efficiency approaching 18.6% at 420 nm and a solar-to-fuel efficiency of 2.8%. Excellent photocatalytic stability is maintained over ten consecutive reaction cycles with negligible structural degradation. This work demonstrates how dual single-atom engineering integrated with crystalline COF/g-C3N4 heterostructures provides a powerful strategy for constructing next-generation artificial photosynthetic systems capable of simultaneously producing solar fuels and green hydrogen with exceptional efficiency.
Source: ChemRxiv
Language: English
Field: Energy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7167286325