As pioneering materials, single atom catalysts (SACs) have demonstrated exceptional potential across a plethora of domains ranging from biomedicine to energy conversion, environmental preservation, and marine energy. The comprehensive review delves into the latest research advancements in the practical applications of SACs, meticulously dissecting their underlying principles, distinctive features, and versatile applications. Tailoring their operational paradigms to suit diverse application contexts, we elaborate on the operational mechanisms of SACs, accentuating their unparalleled catalytic efficacy and structural resilience. The review systematically delineates the design strategies for various SAC variations, encompassing prevalent materials alongside tactics to fortify their adaptability to environmental conditions and ensure enduring operational stability. Delving further, we scrutinized the potential domains, where SACs demonstrate breakthrough potential in biomedical targeted therapy, efficient energy electrocatalysis, and the deep degradation of pollutants by maximizing atomic utilization and controlling the coordination microenvironment. Conclusively, we deliberate on the challenges confronting SACs with regards to their catalytic prowess, proposing future trajectories and methodologies to amplify their ubiquitous deployment and further refine their efficacy in real-world applications.

Photoelectrochemical syngas production using photoanode-driven systems from aqueous CO₂ is a promising technology. To address the challenge of poor selectivity caused by the wide band gap of photoelectrode, we introduce a novel photoanode, PDI/Cu₂O/Cu, where PDI is the perylene tetracarboxylic di-(propyl imidazole). Using Cu₂O as a substrate enhances charge transfer kinetics, while PDI modification mitigates photocorrosion and augments photoelectrochemical CO₂ reduction reaction (PEC CO₂RR) activity. This enhancement stems from PDI’s narrow band gap and efficient visible light absorption. The syngas production achieved a noteworthy 124.47 μmol/(cm²·h) at 1.57 V vs. RHE, making it an optimal feedstock gas for hydrocarbon synthesis. Detailed UV–vis spectra indicate that layered structure significantly improves the absorption edge of the photoanode, facilitating enhanced utilization of visible light. Additionally, the electron lifetime of the PDI/Cu₂O/Cu photoanode is substantially increased which is also one of the factors affecting the reactivity, as demonstrated by the Bode phase plot.

Elaborated design of catalytic systems with a specifically tailored site distance to match the intermediates could substantially improve reaction kinetics and boost catalytic activity under unfavorable reaction conditions. Considering the lower energy barriers of water splitting upon the synergy of dual sites, constructing synergistic Pt-M (M: transition metal) dual sites is an effective way to boost Pt with highly catalytic hydrogen evolution reaction (HER) performance. An unconventional “Ni(OH)₂-coated high-index Pt facets” was constructed to obtain long-range Pt-Ni dual sites, in which Ni composition as a water dissociation synergistic site can protect Pt from electrolyte corrosion and ensure efficient proton donation to Pt sites. The obtained long-range Pt-Ni dual sites present 3.84 mA·cm⁻¹ of current density, which is 7.5 times specific activity higher than that of commercial Pt/C towards alkaline HER. The enhanced HER performance is attributed to synergistic catalysis on Pt-Ni dual sites accompanied by unconventional electron coupling. This work illustrates a new strategy to construct the long-range dual sites by unconventional strategy for fundamental electrocatalytic study of alkaline HER.