Water‐Splitting Electrocatalysis in Acid Conditions Using Ruthenate‐Iridate Pyrochlores

Abstract

The pyrochlore solid solution (Na0.33Ce0.67)2(Ir1−xRux)2O7 (0≤x≤1), containing B-site RuIV and IrIV is prepared by hydrothermal synthesis and used as a catalyst layer for electrochemical oxygen evolution from water at pH<7. The materials have atomically mixed Ru and Ir and their nanocrystalline form allows effective fabrication of electrode coatings with improved charge densities over a typical (Ru,Ir)O2 catalyst. An in situ study of the catalyst layers using XANES spectroscopy at the Ir LIII and Ru K edges shows that both Ru and Ir participate in redox chemistry at oxygen evolution conditions and that Ru is more active than Ir, being oxidized by almost one oxidation state at maximum applied potential, with no evidence for ruthenate or iridate in +6 or higher oxidation states.

Electro-oxidation of a cobalt based steel in LiOH: a non-noble metal based electro-catalyst suitable for durable water-splitting in an acidic milieu

“…In particular, the stability of non-noble-metal-based electrocatalysts towards oxidative water-splitting of acids needs to be optimized. [20][21][22][23][24][25][26][27] Therefore, the develop-ment of electrocatalysts solely based on nonprecious metals suitable for robust and efficient anodic water-splitting in the acidic regime is of the highest interest, 22 and certainly rep-resents the topic of ongoing research in many groups. Surface modified steels are known to be efficient, stable, cheap and easily accessible electrode materials ideally suited for the electrochemically driven cleavage of water into its elements.…”

An electronic approach to minimising moisture-associated skin damage in ostomy patients

“…2) which can actively measure the pH and respond accordingly. The electrochemical control of processes that involve either the production of protons (H + ) or their consumption (and hence enable pH manipulation) have been successfully demonstrated in a number of electroanalytical [29,30] and electroporation systems [31][32][33][34] but the underpinning reactions are now being extensively researched in solar conversion and hydrogen fuel cell technologies [35][36][37][38][39][40][41]. Our contention is that these processes which, in principle, can lead to changes in pH profile at the electrode, could be harnessed to control the pH at the skin surface.…”

“…A critical factor will be the large potentials required to generate the protons necessary to lower the pH. There has been a tremendous effort to improve the electrochemical performance with regard to energy systems [35][36][37][38][39][40][41][42][43] but it could be expected that there are translational opportunities through which the system proffered in Fig. 2 could benefit.…”

“…Presently, it is recognised that these reactions occur at a high rate on platinum, ruthenium and iridium-based catalysts [35][36][37][38], though their inclusion within the proposed context is clearly far from cost-effective as the conductive mesh would need to be disposable in keeping with the conventional ostomy management [7,8,47]. Such issues of cost are consonant with those relative to more economically viable energy systems and the availability of inexpensive catalytic materials that can facilitate the oxygen evolution reaction (OER) is currently a critical bottleneck [35,36]. A large number of the approaches have examined the OER in either highly alkaline or acidic systems [35][36][37][38] which would clearly be unsuitable for application within an ostomy appliance.…”

“…Such issues of cost are consonant with those relative to more economically viable energy systems and the availability of inexpensive catalytic materials that can facilitate the oxygen evolution reaction (OER) is currently a critical bottleneck [35,36]. A large number of the approaches have examined the OER in either highly alkaline or acidic systems [35][36][37][38] which would clearly be unsuitable for application within an ostomy appliance. Nevertheless, there is an increasing interest in the use of catalysts operating within mildly acidic and neutral conditions [39][40][41][42][43] which would be much more applicable in the present context.…”