Nanophase-Separated Copper-Zirconia Composites for Bifunctional Electrochemical CO2 Conversion to Formic Acid.

A copper-zirconia composite having an evenly distributed lamellar texture, Cu#ZrO2, was synthesized by promoting nanophase separation of the Cu51Zr14 alloy precursor in a mixture of carbon monoxide (CO) and oxygen (O2). High-resolution electron microscopy revealed that the material consists of interchangeable Cu and t-ZrO2 phases with an average thickness of 5 nm. Cu#ZrO2 exhibited enhanced selectivity toward the generation of formic acid (HCOOH) by electrochemical reduction of carbon dioxide (CO2) in aqueous media at a Faradaic efficiency of 83.5% at -0.9 V versus the reversible hydrogen electrode. In situ Raman spectroscopy has revealed that a bifunctional interplay between the Zr4+ sites and the Cu boundary leads to amended reaction selectivity along with a large number of catalytic sites.

Visible-light-driven dry reforming of methane using a semiconductor-supported catalyst.

Dry reforming of methane (DRM) is an attractive reaction that consumes two major greenhouse gases while producing the industrially important components of syngas. In this study, various semiconductors were examined as light-harvesting support materials to promote catalytic DRM reaction under mild conditions. Among the metal-loaded catalysts, rhodium-loaded tantalum oxynitride (Rh/TaON) drove the DRM reaction even under visible light irradiation (>400 nm), and its activity exceeded the thermal catalyst limit. According to our spectroscopic analysis and the surface temperature measurement, the bandgap excitation of TaON dominantly promotes the DRM reaction in addition to its photo-thermal effect.

Mesoporous Rh Emerging from Nanophase-separated Rh-Y Alloy.

Mesoporous precious metals with abundant active sites and high surface area have been widely recognized as high-performance catalytic materials. However, the templated synthesis is complex and costly. Herein, we report a mesoporous rhodium (m-Rh) that can be readily synthesized from entangled nanofibres of Rh and Y2 O3 without templates. The entangled nanofibres, prepared from uniform Rh-Y alloys under redox atmosphere, were the key precursor in the synthesis processes. Moreover, the m-Rh efficiently catalyzed carbon dioxide reforming of methane (DRM) at a low reaction temperature of 683 K. Further, electrochemical methods of CO electro-oxidation were innovatively used to demonstrate the stability of CO and oxygen species for the DRM reaction.

Topologically immobilized catalysis centre for long-term stable carbon dioxide reforming of methane.

Methane reforming at low temperatures is of growing importance to mitigate the environmental impact of the production of synthesis gas, but it suffers from short catalyst lifetimes due to the severe deposition of carbon byproducts. Herein, we introduce a new class of topology-tailored catalyst in which tens-of-nanometer-thick fibrous networks of Ni metal and oxygen-deficient Y2O3 are entangled with each other to form a rooted structure, i.e., Ni#Y2O3. We demonstrate that the rooted Ni#Y2O3 catalyst stably promotes the carbon-dioxide reforming of methane at 723 K for over 1000 h, where the performance of traditional supported catalysts such as Ni/Y2O3 diminishes within 100 h due to the precluded mass transport by accumulated carbon byproducts. In situ TEM demonstrates that the supported Ni nanoparticles are readily detached from the support surface in the reaction atmosphere, and migrate around to result in widespread accumulation of the carbon byproducts. The long-term stable methane reforming over the rooted catalyst is ultimately attributed to the topologically immobilized Ni catalysis centre and the synergistic function of the oxygen-deficient Y2O3 matrix, which successfully inhibits the accumulation of byproducts.

Strontium Titanate Based Artificial Leaf Loaded with Reduction and Oxidation Cocatalysts for Selective CO2 Reduction Using Water as an Electron Donor.

Thin film of SrTiO3 nanorods loaded with reduction and oxidation cocatalysts drove the selective reduction of carbon dioxide (CO2) into carbon monoxide (CO), as well as caused the production of equivalent oxygen molecules through water oxidation under UV irradiation. The described film functioned as a free-standing plate without any bias potential application, similar to a natural leaf. The film was facilely fabricated by a simple hydrothermal and annealing treatment of a titanium substrate to produce the SrTiO3 nanorod film (STO film) followed by two steps of loading the reduction and oxidation cocatalysts onto the surface of the STO. As a reduction cocatalyst, a CuxO nanocluster was chosen to achieve selective reduction of CO2 into CO, whereas a cobalt- and phosphate-based cocatalyst (CoPi) facilitated oxidation on the STO surface to promote oxygen generation. For the photocatalysis test, a wireless film was simply set into an aqueous solution bubbled with CO2 in a reactor, and CO production was observed in the headspace of the reactor under UV irradiation. Compared to the bare STO film, the dual cocatalyst-loaded STO film exhibited 2.5 times higher CO generation. H2 production was very limited in our system, and the amount of molecules generated by the reduction reaction was almost twice that of the generated oxygen molecules, proving that water molecules acted as electron donors. Our artificial leaf consists of abundant and nontoxic natural elements and represents the first achievement of stoichiometric CO2 reduction using water as an electron donor by a free-standing natural leaflike plate form.