Mixed bimetallic oxides offer great opportunities for a systematic tuning of electrocatalytic activity and stability. Here, we demonstrate the power of this strategy using well-defined thermally prepared Ir–Ni mixed oxide thin film catalysts for the electrochemical oxygen evolution reaction (OER) under highly corrosive conditions such as in acidic proton exchange membrane (PEM) electrolyzers and photoelectrochemical cells (PEC). Variation of the Ir to Ni ratio resulted in a volcano type OER activity curve with an unprecedented 20-fold improvement in Ir mass-based activity over pure Ir oxide. In situ spectroscopic probing of metal dissolution indicated that, against common views, activity and stability are not directly anticorrelated. To uncover activity and stability controlling parameters, the Ir–Ni mixed thin oxide film catalysts were characterized by a wide array of spectroscopic, microscopic, scattering, and electrochemical techniques in conjunction with DFT theoretical computations. By means of an in...

Molecular insight in structure and activity of highly efficient, low-Ir Ir-Ni oxide catalysts for electrochemical water splitting (OER)

Easily oxidizable substances inside human diploid fibroblast cell strains were monitored amperometrically with a platinized carbon-fiber microelectrode The experiment involved positioning a microelectrode over a single biological cell, forcing the electrode tip into the cell via micromanipulator control, and measuring the transient current corresponding to the complete electrolysis of electroactive species released by the cell A second series of experiments involved puncturing a hole into the cell with a micropipet and measuring the transient current corresponding to the complete electrolysis of electroactive species emitted by the cell with an electrode positioned above the cell The selectivity of both amperometric measurements was demonstrated through the use of known hydrogen peroxide scavengers (added catalase or intracellular peroxidase + added o-dianisidine) to the media bathing the cells The abolition of the amperometric signal under these conditions suggested that hydrogen peroxide was the primary substance detected The magnitude and the time course of the transient current measured implied that the hydrogen peroxide detected was not only that initially present in the cell before its membrane was pierced but represented mostly an oxidative stress response of the cell to its injury

Monitoring an oxidative stress mechanism at a single human fibroblast

Recent Developments of Microenvironment Engineering of Single-Atom Catalysts for Oxygen Reduction toward Desired Activity and Selectivity

Heterogeneous catalysts often undergo structural transformations when they operate under thermal reaction conditions. These transformations are reflected in their evolving catalytic activity, and a fundamental understanding of the changing nature of active sites is vital for the rational design of solid materials for applications. Beyond thermal catalysis, both photocatalysis and electrocatalysis are topical because they can harness renewable energy to drive uphill reactions that afford commodity chemicals and fuels. Although structural transformations of photocatalysts and electrocatalysts have been observed in operando, the resulting implications for catalytic behaviour are not fully understood. In this Review, we summarize and compare the structural evolution of solid thermal catalysts, electrocatalysts and photocatalysts. We suggest that well-established knowledge of thermal catalysis offers a good basis to understand emerging photocatalysis and electrocatalysis research. Structures and activities of classical heterogeneous catalysts, electrocatalysts and photocatalysts can evolve over time. This Review compares such systems and emphasizes characterization of the true active sites.

Structural transformations of solid electrocatalysts and photocatalysts

https://onlinelibrary.wiley.com/doi/pdf/10.1002/aenm.202101998

Essentials of High Performance Water Electrolyzers – From Catalyst Layer Materials to Electrode Engineering

Despite highly promising characteristics of three-dimensionally (3D) nanostructured catalysts for the oxygen evolution reaction (OER) in polymer electrolyte membrane water electrolyzers (PEMWEs), universal design rules for maximizing their performance have not been explored. Here we show that woodpile (WP)-structured Ir, consisting of 3D-printed, highly-ordered Ir nanowire building blocks, improve OER mass activity markedly. The WP structure secures the electrochemically active surface area (ECSA) through enhanced utilization efficiency of the extended surface area of 3D WP catalysts. Moreover, systematic control of the 3D geometry combined with theoretical calculations and various electrochemical analyses reveals that facile transport of evolved O2 gas bubbles is an important contributor to the improved ECSA-specific activity. The 3D nanostructuring-based improvement of ECSA and ECSA-specific activity enables our well-controlled geometry to afford a 30-fold higher mass activity of the OER catalyst when used in a single-cell PEMWE than conventional nanoparticle-based catalysts.

/pdf/highly-efficient-oxygen-evolution-reaction-via-facile-bubble-oyu05kf82p.pdf

Donghoon Lim

Papers

Highly efficient oxygen evolution reaction via facile bubble transport realized by three-dimensionally stack-printed catalysts.

Bioanalytical chemistry with scanning electrochemical microscopy