Tuning the Electronic Structure of Se via Constructing Rh-MoSe₂ Nanocomposite to Generate High-Performance Electrocatalysis for Hydrogen Evolution Reaction

As one of the most promising acid-stable catalysts for hydrogen evolution reaction (HER), MoSe₂ was hampered by the limited quantity of active sites and poor conductivity, which severely impede the efficiency of hydrogen production. Different from heteroatoms doping and conductivity improvement, to address this issues, the electronic structure of active edge sites Se in MoSe₂ were modulated by electron injection from ruthenium deposited on MoSe₂ nanosheets. The Rh-MoSe₂ nanocomposite exhibits great performance enhancement with a low onset potential of 3 mV and quite low overpotential of 31 mV (vs RHE), which is superior to almost all Rh-based and MoSe₂-based electrocatalysts. Experimental results and density functional theory (DFT) simulations reveal that the performance improvement stems from the modulated electronic structure of Se atoms at the edge sites by electron transfer from metal Rh to MoSe₂ support, which leads to a moderate Δ<i>G</i>_H* value of 0.09 eV compared to 0.83 eV for MoSe₂ and −0.26 eV for Rh

Fast Kinetics of Hydrogen Oxidation Reaction on Single-Atom Ce-Alloyed Ru in Alkaline Electrolytes

The kinetics of anodic hydrogen oxidation reaction (HOR) in alkaline media, even catalyzed by the state-of-the-art Pt catalysts, is much lower than that in acidic electrolytes, which is a significant barrier for the development of high-performance anion-exchange membrane fuel cells (AEMFCs). Based on the difference in catalytic mechanism under alkaline and acidic conditions, we suggest that the sluggish HOR in alkaline media is due to the involvement of hydroxyl in Heyrovsky or Volmer steps, and this can be improved by forcing HOR on active sites via the mechanism like that in acidic media. Herein, we prepared a single-atom Ce-alloyed Ru catalyst (Ce1Ru/C) in which Ce atoms could adsorb abundant OH– owing to its much stronger oxophilicity compared to that of Ru. Therefore, the nearest neighbor Ru atoms around Ce atoms become the adsorption sites for Had which would react with the surrounding adsorbed water to form H3O+ad. A key H3O+ad intermediate on the surface of Ce1Ru/C during HOR in alkaline media was detected by in situ Raman spectroscopy, providing direct evidence for the HOR in alkaline media occurring via steps similar to those in acidic media. Even at 30 mV overpotential, Ce1Ru/C still displays rapid reaction kinetics with high mass and specific activity about 27/59 and 5/12 times higher than those of Pt/C and PtRu/C. The activity of our catalyst is the best among various alkaline HOR electrocatalysts reported so far. Moreover, Ce1Ru/C demonstrates high electrochemical stability and CO tolerance, taking a giant step forward toward the commercialization of AEMFCs

Core–Shell Metal-Organic Frameworks as Fe²⁺ Suppliers for Fe²⁺-Mediated Cancer Therapy under Multimodality Imaging

Integrated theranostic agents can provide comprehensive and efficient tools for simultaneous cancer diagnosis and therapy; however, limitations on efficiency and safety offer great room for improvement. Artesunate (AS), as an iron-dependent drug, has been investigated in cancer therapy, depending on free-radical generation for its action, which may reduce side effects commonly associated with conventional chemotherapy agents with low selectivity to target tumors. However, rapid clearance of its free form and limited availability of Fe ion in tumor sites become the main bottlenecks in cancer therapy. Herein, core–shell Mn₃[Co­(CN)₆]₂@MIL-100­(Fe) metal-organic frameworks (CS-MOFs) nanocube was designed using a layer-by-layer method, which holds great potential for synchronous co-delivery of AS and ferric ions for cancer therapy. Moreover, the heterogeneous hybrid CS-MOFs show single- and two-photon fluorescence, together with T₂ and enhanced T₁ magnetic resonance imaging ability. pH-responsive degradation of CS-MOFs enables on-demand Fe­(III) and AS release in the tumor microenvironment. The intracellular ferric ions will further be reduced to ferrous ion that catalyze AS to generate carbon-centered free radicals and reactive oxygen species (ROS). The potential of this alternative antitumor modality under multimodality imaging is demonstrated both <i>in vitro</i> and <i>in vivo</i>. In addition, compared with free AS alone, the nanodrug system CS-MOFs@AS shows significantly enhanced tumor delivery specificity and negligible long-term toxicity. <i>In vivo</i> therapy results indicate that the antitumor efficacy of CS-MOFs@AS was 5.79 times greater than that of free AS, making it a promising Fe²⁺-mediated drugs delivery system