Isothermal Reduction of IrO2(110) Films by Methane Investigated Using In Situ X-ray Photoelectron Spectroscopy

Morphological and Coordination Modulations in Iridium Electrocatalyst for Robust and Stable Acidic OER Catalysis

Proton exchange membrane water splitting (PEMWS) technology has high-level current density, high operating pressure, small electrolyzer-size, integrity, flexibility, and has good adaptability to the volatility of wind power and photovoltaics, but the development of both active and high stability of the anode electrocatalyst in acidic environment is still a huge challenge, which seriously hinders the promotion and application of PEMWS. In recent years, researchers have made tremendous attempts in the development of high-quality active anode electrocatalyst, and we summarize some of the research progress made by our group in the design and synthesis of PEMWS anode electrocatalysts with different nanostructures, and makes full use of electrocatalytic activity points to increase the inherent activity of Iridium (Ir) sites, and provides optimization strategies for the long-term non-decay of catalysts under high anode potential in acidic environments. At this stage, these research advances are expected to facilitate the research and technological progress of PEMWS, and providing some research ideas and references for future research on efficient and inexpensive PEMWS anode electrocatalysts.

Operando CO Infrared Spectroscopy and On-Line Mass Spectrometry for Studying the Active Phase of IrO2 in the Catalytic CO Oxidation Reaction

We combine operando diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) with on-line mass spectrometry (MS) to study the correlation between the oxidation state of titania-supported IrO2 catalysts (IrO2@TiO2) and their catalytic activity in the prototypical CO oxidation reaction. Here, the stretching vibration of adsorbed COad serves as the probe. DRIFTS provides information on both surface and gas phase species. Partially reduced IrO2 is shown to be significantly more active than its fully oxidized counterpart, with onset and full conversion temperatures being about 50 °C lower for reduced IrO2. By operando DRIFTS, this increase in activity is traced to a partially reduced state of the catalysts, as evidenced by a broad IR band of adsorbed CO reaching from 2080 to 1800 cm−1.

Kinetics and selectivity of methane oxidation on an IrO2(110) film

Undercoordinated, bridging O-atoms (O_br) are highly active as H-acceptors in alkane dehydrogenation on IrO₂(110) surfaces but transform to HO_brgroups that are inactive toward hydrocarbons. The low C-H activity and high stability of the HO_brgroups cause the kinetics and product selectivity during CH₄oxidation on IrO₂(110) to depend sensitively on the availability of O_bratoms prior to the onset of product desorption. From temperature programmed reaction spectroscopy (TPRS) and kinetic simulations, we identified two O_br-coverage regimes that distinguish the kinetics and product formation during CH₄oxidation on IrO₂(110). Under excess O_brconditions, when the initial O_brcoverage is greater than that needed to oxidize all the CH₄to CO₂and HO_brgroups, complete CH₄oxidation is dominant and produces CO₂in a single TPRS peak between 450 and 500 K. However, under O_br-limited conditions, nearly all the initial O_bratoms are deactivated by conversion to HO_bror abstracted after only a fraction of the initially adsorbed CH₄oxidizes to CO₂and CO below 500 K. Thereafter, some of the excess CH_xgroups abstract H and desorb as CH₄above ∼500 K while the remainder oxidize to CO₂and CO at a rate that is controlled by the rate at which O_bratoms are regenerated from HO_brduring the formation of CH₄and H₂O products. We also show that chemisorbed O-atoms ('on-top O') on IrO₂(110) enhance CO₂production below 500 K by efficiently abstracting H from O_bratoms and thereby increasing the coverage of O_bratoms available to completely oxidize CH_xgroups at low temperature. Our results provide new insights for understanding factors which govern the kinetics and selectivity during CH₄oxidation on IrO₂(110) surfaces.

Synergetic effect between Pd2+ and Ir4+ species promoting direct ethane dehydrogenation into ethylene over bimetallic PdIr/AC catalysts

This work reported the efficient Pd–Ir pairs on the Pd7Ir2/AC-B catalyst achieved a TOF (C2H4) of 756.6 h−1 at 500 °C, and the direct ethane dehydrogenation (EDH) rationale and deactivation mechanism were proposed.