Tuning Ir d-orbital occupation via doping Cu into the IrO2 lattice to prepare a highly efficient oxygen evolution reaction catalyst, Cu0.3Ir0.7Oδ.

Oxygen evolution reaction (OER) catalysts with high activity are of particular importance for renewable energy production and storage. Here, we prepare Kx≈0.25IrO2 catalyst that exhibits an excellent OER activity compared to IrO2, which is univerally acknoweledged as a state-of-the-art OER catalyst. The prepared catalyst reflects a small overpotential 0.35 V at a current density of 10 mA cm(-2) and a lower Tafel slope (65 mV dec(-1)) compared to that for IrO2 (74 mV dec(-1)). The performed X-ray photoelectron spectroscopy (XPS) and X-ray adsorption (XAS) experiments indicate that the Ir-site of Kx≈0.25IrO2 has a lower valence and more Ir-5d occupied states, suggesting more electrons on the Ir site. The extra electrons located on the Ir site and distorted IrO6 octahedral symmetry have a significant effect on the 5d orbital energy distribution which is verified by our DOS calculation. The performed DFT calculations state that the Kx≈0.25IrO2 essentially obtains good OER performance because it has a lower theoretical overpotential (0.50 V) compared to IrO2 (0.61 V).

Tuning the nature and profile of acidic and basic sites on the surface of redox-active metal oxide nanostructures is a promising approach to constructing efficient catalysts for the oxidative removal of chlorinated volatile organic compounds (CVOCs). Herein, using dichloromethane (DCM) oxidation as a model reaction, we report that phosphate (PO x ) Brønsted acid sites can be incorporated onto a CeO 2 nanosheet (NS) surface via an organophosphate-mediated route, which can effectively enhance the CeO 2 's catalytic performance by promoting the removal of chlorine poisoning species. From the systematic study of the correlation between PO x composition, surface structure (acid and basic sites), and catalytic properties, we find that the incorporated Brønsted acid sites can also function to decrease the amount of medium-strong basic sites (O 2− ), reducing the formation of chlorinated organic byproduct monochloromethane (MCM) and leading to the desirable product, HCl. At the optimized P/Ce ratio (0.2), the PO x −CeO 2 NSs can perform a stable DCM conversion of 65−70% for over 10 h at 250 °C and over 95% conversion at 300 °C, superior to both pristine and other phosphate-modified CeO 2 NSs. Our work clearly identifies the critical role of acid and basic sites over functionalized CeO 2 for efficient catalytic CVOCs oxidation, guiding future advanced catalyst design for environmental remediation.

Synthesizing solid solutions of IrO 2 via doping is known to be a viable approach for effectively using iridium metal by enhancing its intrinsic properties. However, such composites at certain fractional values of dopants realize the substitution limit because of lattice mismatch. Here, on the basis of density functional theory studies and experimentation, we demonstrate codoping as an effective approach to overcome this result with an outstanding oxygen evolution reaction (OER) activity. Nickel and cobalt as the case dopants for the host structure IrO 2 atomically substituted 50% of the precious metal. As a new structural insight, the decreased crystal energy was determined to be the key factor for considerable insertion of dopants. Furthermore, the synthesized codoped IrO 2 reflected an overpotential of only 285 mV at a current density of 10 mA•cm −2 , which is appreciably lower than the 320 and 330 mV for individually doping cobalt and nickel, respectively. Our presented approach suggests further OER optimization methods with extensive reduction of precious metals.

Atom-thick van der Waals heterostructures with nontrivial physical properties tunable via the magnetoelectric coupling effect are highly desirable for the future advance of multiferroic devices. In this work on LaCl/In2Se3 heterostructure consisting of a 2D ferromagnetic layer and a 2D ferroelectric layer, reversible switch of the easy axis and the Curie temperature of the magnetic LaCl layer has been enabled by switching of ferroelectric polarization in In2Se3. More importantly, magnetic skyrmions in the bimerons form have been discovered in the LaCl/In2Se3 heterostructure and can be driven by an electric current. The creation and annihilation of bimerons in LaCl magnetic nanodisks were achieved by polarization switching. It thus proves to be a feasible approach to achieve purely electric control of skyrmions in 2D van der Waals heterostructures. Such nonvolatile and tunable magnetic skyrmions are promising candidates for information carriers in future data storage and logic devices operated under small electrical currents.