Engineering Polarization in the Ferroelectric Electrocatalysts to Boost Water Electrolysis

Water splitting is the most important process for making green hydrogen. The positive effects of ferroelectric polarization in various kinds of water splitting are well recognized, but the study of electrocatalytic water splitting is still in its infancy. Herein, a family of intrinsic ferroelectrics with a flexible tetragonal tungsten bronze structure is chosen to accommodate oxygen evolution reaction (OER) active sites together with its freedom for tuning the ferroelectric polarization. It is found that the OER performance is positively correlated with the ferroelectric polarization, with a significant reduction in the overpotential of ≈40 mV at 10 mA cm−2, coming from two trade-off effects, i.e., enhancement of the surface adsorption and band tilting for fast electron transfer. This study not only fills the gap between electrocatalytic water splitting and the band structure but also proposes ferroelectric polarization as a powerful tool to enhance water splitting for clean hydrogen in several ways

Simultaneous Activation of Different Coordination Sites in Single-Phase FeCoMo3O8 for the Oxygen Evolution Reaction

ABMo3O8 is an emerging oxygen evolution reaction (OER) electrocatalyst, exhibiting dual coordination sites for transition metals with good conductivity. However, it is unclear which sites are active for the OER and how to activate them both. Herein, we demonstrated experimentally that only tetrahedral (Td) Co sites are highly active in Co2Mo3O8, and octahedral (Oh) sites are activated by introducing Fe. Various synchrotron X-ray based spectroscopies confirmed the allocation of Co2+ at Td and Fe2+ at Oh sites. The dual activation of different sites improved the OER efficiency with overpotentials of 308 mV@10 mA cm-2 and 361 mV@100 mA cm-2. This unique structure with corner-shared Td Co and Oh Fe in high spin states increases the active site numbers, produces synergistic effects, optimizes the adsorption of intermediates, and creates an unobstructed spin channel for electron transfer. This work provides an effective strategy to design a pair of OER catalysts by coordination engineering

Interface-coupling of CoFe-LDH on MXene as high-performance oxygen evolution catalyst

Oxygen evolution reaction (OER) is the bottleneck reaction of the overall water splitting process despite the intensive research in the past decades. Efficient yet stable low-cost OER catalysts have been widely explored but further improvement is still highly demanded. Herein, a type of hybrid OER catalyst was prepared by the growth of CoFe-LDH (layered double hydroxide) on the surface of Ti 3 C 2 MXene nanosheets, which exhibits superior OER performance than the state-of-the-art RuO 2 . The enhancement of the OER performance could be attributed to the combination of oxygen-breaking ability of CoFe-LDH and metallic conductivity of Ti 3 C 2 MXene substrate. Meanwhile, the direct growth of CoFe-LDH on the hydroxyl-rich surface of MXene effectively prevents itself from aggregation, exposing more CoFe-LDH edge active sites. What\u27s more important is that the intimate interface between CoFe-LDH and Ti 3 C 2 MXene brings in efficient charge transfer and oxygen activation, which is supported by the DFT calculation results. The direct growth of CoFe-LDH on MXene endows the insulating LDH with metallic features with the O 2p states become distributed above the Fermi level which is mediated by the possible anionic redox process. This work demonstrates the great potential of MXene-based hybrid nanostructure for energy conversion applications

Harnessing magnetic fields to accelerate oxygen evolution reaction

The challenge of overcoming the bottleneck in water electrolysis can potentially be addressed by utilizing permanent magnets without extra energy consumption, but the underlying mechanism of magnetic field effects is still puzzling despite increasing efforts in last few years. In this work, by dip-coating a superhydrophilic γ-Fe2O3 layer onto different electrode substrates, their surface wettability and magnetism are modified, so the ever-tangled effects of magnetic field are separated and identified. It is determined that the primary contribution of magnetic fields at the high current density was due to additional Lorentz force and Kelvin force exerted on oxygen gas bubble, with the former being dependent on the external magnetic field\u27s geometry and the latter closely tied to the electrodes’ magnetism. Strategies to maximize effects of magnetic field as well as the overall efficiency of water electrolysis is proposed

Ultrasound-mediated nanobubble destruction (UMND) facilitates the delivery of A10-3.2 aptamer targeted and siRNA-loaded cationic nanobubbles for therapy of prostate cancer

<p>The Forkhead box M1 (FoxM1) transcription factor is an important anti-tumor target. A novel targeted ultrasound (US)-sensitive nanobubble that is likely to make use of the physical energy of US exposure for the improvement of delivery efficacy to target tumors and specifically silence FoxM1 expression appears as among the most potential nanocarriers in respect of drug delivery. In this study, we synthesized a promising anti-tumor targeted FoxM1 siRNA-loaded cationic nanobubbles (CNBs) conjugated with an A10-3.2 aptamer (siFoxM1-Apt-CNBs), which demonstrate high specificity when binding to prostate-specific membrane antigen (PSMA) positive LNCaP cells. Uniform nanoscaled siFoxM1-Apt-CNBs were developed using a thin-film hydration sonication, carbodiimide chemistry approaches, and electrostatic adsorption methods. Fluorescence imaging as well as flow cytometry evidenced the fact that the siFoxM1-Apt-CNBs were productively developed and that they specifically bound to PSMA-positive LNCaP cells. siFoxM1-Apt-CNBs combined with ultrasound-mediated nanobubble destruction (UMND) significantly improved transfection efficiency, cell apoptosis, and cell cycle arrest <i>in vitro</i> while reducing FoxM1 expression. <i>In vivo</i> xenografts tumors in nude-mouse model results showed that siFoxM1-Apt-CNBs combined with UMND led to significant inhibition of tumor growth and prolonged the survival of the mice, with low toxicity, an obvious reduction in FoxM1 expression, and a higher apoptosis index. Our study suggests that siFoxM1-Apt-CNBs combined with UMND might be a promising targeted gene delivery strategy for therapy of prostate cancer.</p