Science Bulletin最新文献

Electrochemical two-electron oxygen reduction reaction (2e^- ORR) serves as an appealing approach for green hydrogen peroxide (H₂O₂) production. However, the corresponding progress in efficient non-precious metal catalysts for acidic 2e^- ORR has not kept pace, with the research model being almost confined to Co-based system. Here, guided by molecular dynamics simulations, the active nature and origin of pyrolyzed Cr-N₄ catalysts for ORR are unveiled, wherein the over-strong oxygen affinity of the Cr center is counterbalanced by a spontaneous axial O-coordination. By creating an oxidation-induced electron-deficient environment, the Cr-N₄ can be flexibly tailored for selective H₂O₂ formation. A single-atom Cr-N₄/C(O) catalyst is developed experimentally, which rivals and even slightly outperforms its Co-based counterpart in terms of selectivity (92% versus 71%) and productivity (202 versus 145 mmol g_cat^-1 h^-1) for H₂O₂. More encouragingly, the Cr-based catalysts exhibit minimal reactivity towards H₂O₂-related side reactions, with the metal component being robust against leaching. This research marks the first identification of pyrolyzed Cr-N₄ catalysts as competent for acidic two-electron O₂ reduction to H₂O₂. The innovative models and insights offer profound guidance for the design of future-generation catalysts for electrochemical H₂O₂ synthesis.

Refractory wounds (RWs) are a common and severe complication of many diseases; however, the existing therapeutic methods are unsatisfactory in clinical practice. Here, we observed significant downregulation of the hepatocyte growth factor (HGF) in plasma samples from patients with autoimmune diseases. We used electroporation to deliver a plasmid containing HGF to induce its overexpression on mesenchymal stromal cells (MSC^HGF) and loaded them into an injectable hydrogel to treat RWs in patients with clinical autoimmunity. The MSC^HGF exhibited stable HGF expression and secretion. In addition, they displayed a self-reinforcing loop, enhanced migration, and improved anti-apoptosis capacity via the autocrine activation of the c-Met-mediated phosphatidylinositol 3-kinase (PI3K)-protein kinase B (AKT) signaling pathway. Furthermore, the HGF (as well as other bioactive factors) secreted from the MSC^HGF significantly augmented the migration and angiopoiesis of vascular endothelial cells, decreased the cellular inflammation of macrophages, and improved extracellular matrix remodeling in fibroblasts. According to these features, we demonstrated that the MSC^HGF-loaded injectable hydrogel boosted cellular functions and afforded a long-acting healing efficacy in the treatment of clinical autoimmune patients with RWs. Therefore, the genetically engineered MSC^HGF and their dispersed hydrogel system will have clinical significance for wound therapy.

Mg₃(Sb,Bi)₂-based thermoelectrics (TEs) show promise for near-room-temperature energy conversion and TE-cooling applications. However, further improvements in electrical power factors and figure-of-merits (zTs) are constrained by precise Mg-vacancy regulation and elucidation of underlying mechanisms. Herein, we report a novel in-situ Mg-vacancy engineering strategy in Mg₃(Sb,Bi)₂ where excess Mg is generated from local reactions between a selection of specific transition metals and the component anionic element(s) in Mg₃(Sb,Bi)₂ during spark-plasma-sintering. This process effectively refills matrix Mg-vacancies through the subsequent global diffusion of Mg cations in Mg₃(Sb,Bi)₂ lattices. This local-reaction-global-diffusion concept, contrasting with reported mechanisms associated with localized grain-boundary engineering, is elaborated through multiscale investigation. Vacancy-restrained Mg₃(Sb,Bi)₂ demonstrates remarkably enhanced carrier mobility and zTs, achieving record-high power factors. Our fabricated Mg₃Sb_0.5Bi_1.5/MgAgSb and Mg₃SbBi/MgAgSb modules achieve record-high dual-output performance with power-density/efficiency values of 1.23 W cm^-2/11.7% and 1.05 W cm^-2/12.8%, respectively, under a temperature difference (ΔT) of 315 K. The constructed Mg₃Sb_0.5Bi_1.5/Bi_0.5Sb_1.5Te₃ and Mg₃Sb_0.75Bi_1.25/Bi_0.5Sb_1.5Te₃ Peltier modules deliver competitive cooling ΔT_max exceeding 70 and 67 K, respectively, at 303 K. The concept is expected to extend to the defect engineering of other energy materials (e.g., SnTe and PbSe TEs), TE-interface materials, and metal-semiconductor interfaces with optimized functionalities.