Oxygen evolution reaction: a perspective on a decade of atomic scale simulations

Multiple strategies to overcome the intrinsic limitations of the oxygen evolution reaction (OER) have been proposed by numerous research groups. Despite the substantial efforts, the driving force required for water oxidation is largely making the reaction inefficient. In the present work, we collected published studies involving DFT calculations for the OER, with the purpose to understand why the progress made so far, for lowering the overpotential of the reaction, is relatively small. The data revealed that the universal scaling relationship between HO* and HOO* intermediates is still present and robust, despite the variety in methods and structures used for calculating the binding energies of the intermediates. On the other hand, the data did not show a clear trend line regarding the O* binding. Our analysis suggested that trends in doped semiconducting oxides behave very differently from those in other oxides. This points towards a computational challenge in describing doped oxides in a realistic manner. We propose a way to overcome these computational challenges, which can be applied to simulations corresponding to doped semiconductors in general

Lifting the discrepancy between experimental results and the theoretical predictions for the catalytic activity of RuO2 (110) towards Oxygen Evolution Reaction

Developing new efficient catalyst materials for the oxygen evolution reaction (OER) is essential for widespread proton exchange membrane water electrolyzer use. Both RuO2(110) and IrO2(110) have been shown to be highly active OER catalysts, however DFT predictions have been unable to explain the high activity of RuO2. We propose that this discrepancy is due to RuO2 utilizing a different reaction pathway, as compared to the conventional IrO2 pathway. This hypothesis is supported by comparisons between experimental data, DFT data and the proposed reaction model

Chitosan-co-Hyaluronic acid porous cryogels and their application in tissue engineering

In this work, the usability of chitosan-co-hyaluronic acid cryogels as a tissue-engineering scaffold was investigated. Chitosan-co-hyaluronic acid cryogels were synthesized at subzero temperature. Cryogels which were composed of various compositions of chitosan and hyaluronic acid (0, 10, 20, 30 and 50 wt% hyaluronic acid) was prepared. Morphological studies showed that the macroporous cryogels have been developed with 90-95% porosity. Particularly, the mechanical and biomaterial property of pure chitosan was improved by making copolymer with hyaluronic acid in different concentration. The MIT cell viability results demonstrated that the cryogels have no significant cytotoxicity effect on 3T3 fibroblast and SAOS-2 cells. (C) 2017 Elsevier B.V. All rights reserved

Synergistic effect of p-type and n-type dopants in semiconductors for efficient electrocatalytic water splitting

The main challenge for acidic water electrolysis is the lack of active and stable oxygen evolution catalysts based on abundant materials, which are globally scalable. Iridium oxide is the only material, which is active and stable. However, Ir is extremely rare and far from scalable. There exist both active materials and stable materials, but those that are active are not stable and vice versa. In this work, we present a strategy for making stable materials active. The stable materials are semiconductors that cannot change oxidation state at relevant reaction conditions. Based on DFT calculations, we find that by adding an n-type dopant, semiconductor surfaces can bind oxygen. However, after oxygen is adsorbed, the material is again in a state where it cannot bind or desorb oxygen. By combining n-type and p-type dopants, the reactivity can be tuned so that oxygen can be adsorbed and desorbed under reaction conditions. It turns out that the tuning can be understood from the electrostatic interactions between the dopants as well as between the dopants and the binding site. We experimentally verify that this strategy works in TiO2 by co-doping with different pairs of n- and p-type dopants. This encourages that the co-doping approach can be used to activate stable materials, without intrinsic oxygen evolution activity, to discover new catalysts for acid water electrolysis

Synergistic effect of p-type and n-type dopants in semiconductors for efficient electrocatalytic water splitting

Co-substituting a stable material, e.g. TiO2, with both n- and p-type dopants, allows tuning its reactivity to activate the material for oxygen evolution. This opens up a new design avenue for acid water electrolysis electrocatalysts