Magnetic Hydrogel Microbots for Efficient Pollutant Decontamination and Self-Catalyzed Regeneration in Continuous Flow Systems.

The efficient removal of organic pollutants from water is crucial for protecting human health and the ecosystem. While adsorbent-based approaches offer advantages over traditional chemical and thermal methods, they still suffer from slow adsorption kinetics, high energy demand, and limited material lifespan. Herein, an efficient decontamination platform is introduced, using magnetic hydrogel microbots (MHMs) made from picolitre-sized hydrogel droplets coated with multifunctional magnetic nanoparticles. This approach includes 1) dividing a droplet into smaller microbots to enhance their interaction with sample solution and 2) dynamically spinning these MHMs to generate hydrodynamic flows that actively draw pollutants toward the embedded hydrogel for capture. The MHMs show high decontamination effectiveness in both bulk and continuous flow setups, achieving ≈95% removal efficiency within 3 min. Further integrating MHMs with a non-pressurized fluidic platform enables energy-efficient continuous flow decontamination, removing ≥95% total organic carbon from a complex pollutant mixture at a flow rate surpassing other recent designs. Additionally, the MHMs facilitate self-catalyzed regeneration using an environmentally friendly H2O2 precursor, allowing for long-term and repeated usage. By enabling the unique divide-and-arrest decontamination of toxic pollutants, the multifunctional design holds tremendous promise for on-site wastewater treatment to ensure safe water access for everyone, even in resource-limited environments.

Harmonizing Plasmonic and Photonic Effects to Boost Photocatalytic H2 Production over 550 mmol ⋠h-1 ⋠gcat -1.

Integrating plasmonic nanoparticles with photonic crystals holds immense potential to enhance green hydrogen photosynthesis by amplifying localized electromagnetic field through generating surface plasmons and slow photons. Current plasmonic photonic designs primarily employ semiconductor-based structural backbone deposited with plasmonic nanoparticles. However, the competition between various optical phenomena in these ensembles hinders effective field enhancement rather than facilitating it. This limitation creates a formidable performance bottleneck that retards hydrogen evolution. Herein, we enhance plasmonic catalysis for efficient hydrogen evolution by effectively harmonizing plasmonic and photonic effects. This is achieved by using inert SiO2 opal as a non-photoabsorbing photonic framework. By aligning the excitation wavelengths of surface plasmons and slow photons, our optimized plasmonic photonic crystals demonstrates a remarkable H2 evolution rate of 560 mmol h-1 gAg -1, surpassing bare plasmonic Ag nanoparticles by >106-fold and other high-performance photocatalytic designs by 280-fold. Mechanistic studies highlight the pivotal role of the non-photoabsorbing photonic backbone in facilitating effective light confinement through the photonic effect. This in turn boosts the plasmonic field for enhanced photocatalytic H2 evolution, even without needing additional co-catalysts. Our work offers valuable insights for future design of electromagnetically hot plasmonic catalysts to achieve efficient light-to-chemical transformations in diverse energy, chemical, and environmental applications.

Catalyst-On-Hotspot Nanoarchitecture: Plasmonic Focusing of Light onto Co-Photocatalyst for Efficient Light-To-Chemical Transformation.

Plasmon-mediated catalysis utilizing hybrid photocatalytic ensembles promises effective light-to-chemical transformation, but current approaches suffer from weak electromagnetic field enhancements from polycrystalline and isotropic plasmonic nanoparticles as well as poor utilization of precious co-catalyst. Here, efficient plasmon-mediated catalysis is achieved by introducing a unique catalyst-on-hotspot nanoarchitecture obtained through the strategic positioning of co-photocatalyst onto plasmonic hotspots to concentrate light energy directly at the point-of-reaction. Using environmental remediation as a proof-of-concept application, the catalyst-on-hotspot design (edge-AgOcta@Cu2O) enhances photocatalytic advanced oxidation processes to achieve superior organic-pollutant degradation at ≈81% albeit having lesser Cu2O co-photocatalyst than the fully deposited design (full-AgOcta@Cu2O). Mass-normalized rate constants of edge-AgOcta@Cu2O reveal up to 20-fold and 3-fold more efficient utilization of Cu2O and Ag nanoparticles, respectively, compared to full-AgOcta@Cu2O and standalone catalysts. Moreover, this design also exhibits catalytic performance >4-fold better than emerging hybrid photocatalytic platforms. Mechanistic studies unveil that the light-concentrating effect facilitated by the dense electromagnetic hotspots is crucial to promote the generation and utilization of energetic photocarriers for enhanced catalysis. By enabling the plasmonic focusing of light onto co-photocatalyst at the single-particle level, the unprecedented design offers valuable insights in enhancing light-driven chemical reactions and realizing efficient energy/catalyst utilizations for diverse chemical, environmental, and energy applications.

Chaotropic Nanoelectrocatalysis: Chemically Disrupting Water Intermolecular Network at the Point-of-Catalysis to Boost Green Hydrogen Electrosynthesis.

Efficient green hydrogen production through electrocatalytic water splitting serves as a powerful catalyst for realizing a carbon-free hydrogen economy. However, current electrocatalytic designs face challenges such as poor hydrogen evolution reaction (HER) performance (Tafel slope, 100-140 mV dec-1 ) because water molecules are thermodynamically trapped within their extensive hydrogen bonding network. Herein, we drive efficient HER by manipulating the local water microenvironment near the electrocatalyst. This is achieved by functionalizing the nanoelectrocatalyst's surface with a monolayer of chaotropic molecules to chemically weaken water-water interactions directly at the point-of-catalysis. Notably, our chaotropic design demonstrates a superior Tafel slope (77 mV dec-1 ) and the lowest overpotential (0.3 V at 10 mA cm-2 ECSA ), surpassing its kosmotropic counterparts (which reinforces the water molecular network) and previously reported electrocatalytic designs by up to ≈2-fold and ≈3-fold, respectively. Comprehensive mechanistic investigations highlight the critical role of chaotropic surface chemistry in disrupting the water intermolecular network, thereby releasing free/weakly bound water molecules that strongly interact with the electrocatalyst to boost HER. Our study provides a unique molecular approach that can be readily integrated with emerging electrocatalytic materials to rapidly advance the electrosynthesis of green hydrogen, holding immense promise for sustainable chemical and energy applications.

Surface-Degenerate Semiconductor Photocatalysis for Efficient Water Splitting without Sacrificial Agents via a Reticular Chemistry Approach.

The production of green hydrogen through photocatalytic water splitting is crucial for a sustainable hydrogen economy and chemical manufacturing. However, current approaches suffer from slow hydrogen production (<70 µmol ⋅ gcat -1 ⋅ h-1 ) due to the sluggish four-electrons oxygen evolution reaction (OER) and limited catalyst activity. Herein, we achieve efficient photocatalytic water splitting by exploiting a multifunctional interface between a nano-photocatalyst and metal-organic framework (MOF) layer. The functional interface plays two critical roles: (1) enriching electron density directly on photocatalyst surface to promote catalytic activity, and (2) delocalizing photogenerated holes into MOF to enhance OER. Our photocatalytic ensemble boosts hydrogen evolution by ≈100-fold over pristine photocatalyst and concurrently produces oxygen at ideal stoichiometric ratio, even without using sacrificial agents. Notably, this unique design attains superior hydrogen production (519 µmol ⋅ gcat -1 ⋅ h-1 ) and apparent quantum efficiency up to 13-fold and 8-fold better than emerging photocatalytic designs utilizing hole scavengers. Comprehensive investigations underscore the vital role of the interfacial design in generating high-energy photoelectrons on surface-degenerate photocatalyst to thermodynamically drive hydrogen evolution, while leveraging the nanoporous MOF scaffold as an effective photohole sink to enhance OER. Our interfacial approach creates vast opportunities for designing next-generation, multifunctional photocatalytic ensembles using reticular chemistry with diverse energy and environmental applications.