Selective Catalytic Electro-Oxidation of Water with Cobalt Oxide in Ion Impermeable Reduced Graphene Oxide Porous Electrodes

Hard X-ray imaging and tomography at the Biomedical Imaging and Therapy beamlines of Canadian Light Source

The Biomedical Imaging and Therapy facility of the Canadian Light Source comprises two beamlines, which together cover a wide X-ray energy range from 13 keV up to 140 keV. The beamlines were designed with a focus on synchrotron applications in preclinical imaging and veterinary science as well as microbeam radiation therapy. While these remain a major part of the activities of both beamlines, a number of recent upgrades have enhanced the versatility and performance of the beamlines, particularly for high-resolution microtomography experiments. As a result, the user community has been quickly expanding to include researchers in advanced materials, batteries, fuel cells, agriculture, and environmental studies. This article summarizes the beam properties, describes the endstations together with the detector pool, and presents several application cases of the various X-ray imaging techniques available to users.

Precise Design of TiO2@CoOx Heterostructure via Atomic Layer Deposition for Synergistic Sono-Chemodynamic Oncotherapy

Sonodynamic therapy (SDT), a tumor treatment modality with high tissue penetration and low side effects, is able to selectively kill tumor cells by producing cytotoxic reactive oxygen species (ROS) with ultrasound-triggered sonosensitizers. N-type inorganic semiconductor TiO2 has low ROS quantum yields under ultrasound irradiation and inadequate anti-tumor activity. Herein, by using atomic layer deposition (ALD) to create a heterojunction between porous TiO2 and CoOx, the sonodynamic therapy efficiency of TiO2 can be improved. Compared to conventional techniques, the high controllability of ALD allows for the delicate loading of CoOx nanoparticles into TiO2 pores, resulting in the precise tuning of the interfaces and energy band structures and ultimately optimal SDT properties. In addition, CoOx exhibits a cascade of H2O2→O2→·O2 - in response to the tumor microenvironment, which not only mitigates hypoxia during the SDT process, but also contributes to the effect of chemodynamic therapy (CDT). Correspondingly, the synergistic CDT/SDT treatment is successful in inhibiting tumor growth. Thus, ALD provides new avenues for catalytic tumor therapy and other pharmaceutical applications.

Progress in Anode Stability Improvement for Seawater Electrolysis to Produce Hydrogen

Seawater electrolysis for hydrogen production is a sustainable and economical approach that can mitigate the energy crisis and global warming issues. Although various catalysts/electrodes with excellent activities have been developed for high-efficiency seawater electrolysis, their unsatisfactory durability, especially for anodes, severely impedes their industrial applications. In this review, attention is paid to the factors that affect the stability of anodes and the corresponding strategies for designing catalytic materials to prolong the anode's lifetime. In addition, two important aspects-electrolyte optimization and electrolyzer design-with respect to anode stability improvement are summarized. Furthermore, several methods for rapid stability assessment are proposed for the fast screening of both highly active and stable catalysts/electrodes. Finally, perspectives on future investigations aimed at improving the stability of seawater electrolysis systems are outlined.

Distortion-Induced Interfacial Charge Transfer at Single Cobalt Atom Secured on Ordered Intermetallic Surface Enhances Pure Oxygen Production

In this work, atomic cobalt (Co) incorporation into the Pd2Ge intermetallic lattice facilitates operando generation of a thin layer of CoO over Co-substituted Pd2Ge, with Co in the CoO surface layer functioning as single metal sites. Hence the catalyst has been titled Co1-CoO-Pd2Ge. High-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy confirm the existence of CoO, with some of the Co bonded to Ge by substitution of Pd sites in the Pd2Ge lattice. The role of the CoO layer in the oxygen evolution reaction (OER) has been verified by its selective removal using argon sputtering and conducting the OER on the etched catalyst. In situ X-ray absorption near-edge structure and extended X-ray absorption fine structure spectroscopy demonstrate that CoO gets transformed to CoOOH (Co3+) in operando condition with faster charge transfer through Pd atoms in the core Pd2Ge lattice. In situ Raman spectroscopy depicts the emergence of a CoOOH phase on applying potential and shows that the phase is stable with increasing potential and time without getting converted to CoO2. Density functional theory calculations indicate that the Pd2Ge lattice induces distortion in the CoO phase and generates unpaired spins in a nonmagnetic CoOOH system resulting in an increase in the OER activity and durability. The existence of spin density even after electrocatalysis is verified from electron paramagnetic resonance spectroscopy. We have thus successfully synthesized intermetallic supported CoO during synthesis and rigorously verified the role played by an intermetallic Pd2Ge core in enhancing charge transfer, generating spin density, improving electrochemical durability, and imparting mechanical stability to a thin CoOOH overlayer. Differential electrochemical mass spectrometry has been explored to visualize the instantaneous generation of oxygen gas during the onset of the reaction.

Materials Design and System Innovation for Direct and Indirect Seawater Electrolysis

Green hydrogen production from renewably powered water electrolysis is considered as an ideal approach to decarbonizing the energy and industry sectors. Given the high-cost supply of ultra-high-purity water, as well as the mismatched distribution of water sources and renewable energies, combining seawater electrolysis with coastal solar/offshore wind power is attracting increasing interest for large-scale green hydrogen production. However, various impurities in seawater lead to corrosive and toxic halides, hydroxide precipitation, and physical blocking, which will significantly degrade catalysts, electrodes, and membranes, thus shortening the stable service life of electrolyzers. To accelerate the development of seawater electrolysis, it is crucial to widen the working potential gap between oxygen evolution and chlorine evolution reactions and develop flexible and highly efficient seawater purification technologies. In this review, we comprehensively discuss present challenges, research efforts, and design principles for direct/indirect seawater electrolysis from the aspects of materials engineering and system innovation. Further opportunities in developing efficient and stable catalysts, advanced membranes, and integrated electrolyzers are highlighted for green hydrogen production from both seawater and low-grade water sources.

Improved Electrochemical Alkaline Seawater Oxidation over Cobalt Carbonate Hydroxide Nanowire Array by Iron Doping

Constructing efficient and low-cost oxygen evolution reaction (OER) catalysts operating in seawater is essential for green hydrogen production but remains a great challenge. In this study, we report an iron doped cobalt carbonate hydroxide nanowire array on nickel foam (Fe-CoCH/NF) as a high-efficiency OER electrocatalyst. In alkaline seawater, such Fe-CoCH/NF demands an overpotential of 387 mV to drive 500 mA cm^-2, superior to that of CoCH/NF (597 mV). Moreover, it achieves excellent electrochemical and structural stability in alkaline seawater.