Bioinspired porous three-coordinated single-atom Fe nanozyme with oxidase-like activity for tumor visual identification via glutathione.

Inspired by structures of natural metalloenzymes, a biomimetic synthetic strategy is developed for scalable synthesis of porous Fe-N3 single atom nanozymes (pFeSAN) using hemoglobin as Fe-source and template. pFeSAN delivers 3.3- and 8791-fold higher oxidase-like activity than Fe-N4 and Fe3O4 nanozymes. The high catalytic performance is attributed to (1) the suppressed aggregation of atomically dispersed Fe; (2) facilitated mass transfer and maximized exposure of active sites for the created mesopores by thermal removal of hemoglobin (2 ~ 3 nm); and (3) unique electronic configuration of Fe-N3 for the oxygen-to-water oxidation pathway (analogy with natural cytochrome c oxidase). The pFeSAN is successfully demonstrated for the rapid colorimetric detection of glutathione with a low limit of detection (2.4 nM) and wide range (50 nM-1 mM), and further developed as a real-time, facile, rapid (~6 min) and precise visualization analysis methodology of tumors via glutathione level, showing its potentials for diagnostic and clinic applications.

Electrochemical Etching Switches Electrocatalytic Oxygen Evolution Pathway of IrOx /Y2 O3 from Adsorbate Evolution Mechanism to Lattice-Oxygen-Mediated Mechanism.

Oxygen evolution reaction (OER) plays key roles in electrochemical energy conversion devices. Recent advances have demonstrated that OER catalysts through lattice oxygen-mediated mechanism (LOM) can bypass the scaling relation-induced limitations on those catalysts through adsorbate evolution mechanism (AEM). Among various catalysts, IrOx , the most promising OER catalyst, suffers from low activities for its AEM pathway. Here, it is demonstrated that a pre-electrochemical acidic etching treatments on the hybrids of IrOx and Y2 O3 (IrOx /Y2 O3 ) switch the AEM-dominated OER pathway to LOM-dominated one in alkali electrolyte, delivering a high performance with a low overpotential of 223 mV at 10 mA cm-2 and a long-term stability. Mechanism investigations suggest that the pre-electrochemical etching treatments create more oxygen vacancies in catalysts due to the dissolution of yttrium and then provide highly active surface lattice oxygen for participating OER, thereby enabling the LOM-dominated pathway and resulting in a significantly increased OER activity in basic electrolyte.

Phytate-coordinated nickel foam with enriched NiOOH intermediates for 5-hydroxymethylfurfural electrooxidation.

Manipulating the surface reconstruction of Ni-based catalysts to form NiOOH intermediates is crucial for electrooxidation. Herein, we report a phytate coordination-induced enrichment of NiOOH on phytate-coordinated Ni foam, which exhibited high catalytic performance for 5-hydroxymethylfurfural electro-oxidation. The HMF oxidation rate of 0.76 mmol h-1 outperformed the majority of Ni-based catalysts.

A fundamental viewpoint on the hydrogen spillover phenomenon of electrocatalytic hydrogen evolution.

Hydrogen spillover phenomenon of metal-supported electrocatalysts can significantly impact their activity in hydrogen evolution reaction (HER). However, design of active electrocatalysts faces grand challenges due to the insufficient understandings on how to overcome this thermodynamically and kinetically adverse process. Here we theoretically profile that the interfacial charge accumulation induces by the large work function difference between metal and support (∆Φ) and sequentially strong interfacial proton adsorption construct a high energy barrier for hydrogen transfer. Theoretical simulations and control experiments rationalize that small ∆Φ induces interfacial charge dilution and relocation, thereby weakening interfacial proton adsorption and enabling efficient hydrogen spillover for HER. Experimentally, a series of Pt alloys-CoP catalysts with tailorable ∆Φ show a strong ∆Φ-dependent HER activity, in which PtIr/CoP with the smallest ∆Φ = 0.02 eV delivers the best HER performance. These findings have conclusively identified ∆Φ as the criterion in guiding the design of hydrogen spillover-based binary HER electrocatalysts.

A pH-Responsive Polymer-CeO2 Hybrid to Catalytically Generate Oxidative Stress for Tumor Therapy.

Catalytic generation of reactive oxygen species has been developed as a promising methodology for tumor therapy. Direct O2•- production from intratumor oxygen exhibits exceptional tumor therapeutic efficacy. Herein, this therapy strategy is demonstrated by a pH-responsive hybrid of porous CeO2 nanorods and sodium polystyrene sulfonate that delivers high oxidative activity for O2•- generation within acidic tumor microenvironments for chemodynamic therapy and only limited oxidative activity in neutral media to limit damage to healthy organs. The hydrated polymer-nanorod hybrids with large hydrodynamic diameters form nanoreactors that locally trap oxygen and biological substrates inside and improve the charge transfer between the catalysts and substrates in the tumor microenvironment, leading to enhanced catalytic O2•- production and consequent oxidation. Together with successful in vitro and in vivo experiments, these data show that the use of hybrids provides a compelling opportunity for the delivery selective chemodynamic tumor therapy.

Amine-Modulated/Engineered Interfaces of NiMo Electrocatalysts for Improved Hydrogen Evolution Reaction in Alkaline Solutions.

The interface between electrolytes and electrocatalysts would largely determine their corresponding activity and stability. Herein, modulating the surface characteristics of NiMo nanoparticles by various adsorbed amines gives the tunability on their interfacial properties and subsequently improves their catalytic performance for hydrogen evolution reaction (HER) in alkaline solutions. Diamines can significantly improve their HER activity by decreasing the charge-transfer resistance and modulating the electronic structures of interfacial active sites. Importantly, among various amines, ethylenediamine facilitates the HER activity of NiMo with a remarkable decrease of 268 mV in the overpotential to reach 10 mA cm-2 as compared with that of the unmodified NiMo in 1.0 M KOH. This method provides a novel strategy of regulating the interfacial properties to strengthen the catalytic performance of electrocatalysts.