Circular economy (CE) is critical to future manufacturing, as it will foster regenerative systems and pave the way for sustainable practices in advanced manufacturing, especially additive manufacturing (AM). Currently, the widespread implementation of CE in the field of AM has been hindered mostly by limitations in materials and technologies. More research efforts need to be dedicated to understanding and evaluating AM's role in facilitating closed-loop resource flow in industrial ecosystems. This article provides a state-of-the-art review of recently published research studies on this topic, ranging from AM recyclable material design and development to AM-assisted repair and remanufacturing. Additionally, current knowledge gaps are identified, and some future research directions are discussed. This review article is expected to serve as a valuable resource for researchers, practitioners, policymakers, and industry professionals who seek to leverage AM technologies in a sustainable manner.

Regulating the rational wettability on gas-diffusion electrodes (GDEs) plays a pivotal role to improve the efficiency of CO₂RR via fine-tuning the reaction zone and boosting the formation of triple-phase interfaces. Herein, we present a wettability regulation strategy that modulates the triple-phase reaction zone in the catalyst layer of GDEs. This strategy was employed on a flow-through hollow fiber GDE coated with a Bi-embedded catalyst layer. Compared to other ex-situ methods (e.g., adding wetting agents) affecting the bulk of electrocatalysts or catalyst layer, we create distinctive hydrophilic-hydrophobic regions within the catalyst layer. Catalyst layer with hydrophilic-hydrophobic regions outperforms the fully hydrophilic one by facilitating the species transport, boosting triple-phase interface formation, and maximizing the active sites. This regulation strategy showed stable wettability during CO₂RR cathodic conditions, evidenced by the direct measurement of penetration depth. The electrode with the regulated wettability exhibited over 80% catalyst utilization and 4 times higher formate partial current density (~150 mA cm⁻² with FE_formate> 90%) compared to the untreated electrode, outperforming other GDEs employed for CO₂RR to formate in the same concentrations of bicarbonate. The finding of this versatile microenvironment regulation strategy can be extended to GDEs used for other gas-phase reactions.