Insights into Ru-Based Molecular Water Oxidation Catalysts: Electronic and Noncovalent-Interaction Effects on Their Catalytic Activities

2013 ◽  
Vol 52 (14) ◽  
pp. 7844-7852 ◽  
Author(s):  
Lele Duan ◽  
Lei Wang ◽  
A. Ken Inge ◽  
Andreas Fischer ◽  
Xiaodong Zou ◽  
...  
Keyword(s):  
Water Oxidation ◽  
Interaction Effects ◽  
Noncovalent Interaction ◽  
Molecular Water ◽  
Oxidation Catalysts ◽  
Catalytic Activities

scholarly journals Design of Molecular Water Oxidation Catalysts Stabilized by Ultrathin Inorganic Overlayers—Is Active Site Protection Necessary?

Inorganics ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 105 ◽  
Author(s):  
Laurent Sévery ◽  
Sebastian Siol ◽  
S. Tilley
Keyword(s):  
Water Oxidation ◽  
Atomic Layer ◽  
Deposition Process ◽  
Operating Conditions ◽  
Molecular Water ◽  
Side Reactions ◽  
Aqueous Environment ◽  
Oxidation Catalysts ◽  
Initial Onset ◽  
Anchoring Groups

Anchored molecular catalysts provide a good step towards bridging the gap between homogeneous and heterogeneous catalysis. However, applications in an aqueous environment pose a serious challenge to anchoring groups in terms of stability. Ultrathin overlayers embedding these catalysts on the surface using atomic layer deposition (ALD) are an elegant solution to tackle the anchoring group instability. The propensity of ALD precursors to react with water leads to the question whether molecules containing aqua ligands, such as most water oxidation complexes, can be protected without side reactions and deactivation during the deposition process. We synthesized two iridium and two ruthenium-based water oxidation catalysts, which contained an aqua ligand (Ir–OH2 and Ru–OH2) or a chloride (Ir–Cl and Ru–Cl) that served as a protecting group for the former. Using a ligand exchange reaction on the anchored and partially embedded Ru–Cl, the optimal overlayer thickness was determined to be 1.6 nm. An electrochemical test of the protected catalysts on meso-ITO showed different behaviors for the Ru and the Ir catalysts. The former showed no onset difference between protected and non-protected versions, but limited stability. Ir–Cl displayed excellent stability, whilst the unprotected catalyst Ir–OH2 showed a later initial onset. Self-regeneration of the catalytic activity of Ir–OH2 under operating conditions was observed. We propose chloride ligands as generally applicable protecting groups for catalysts that are to be stabilized on surfaces using ALD.

scholarly journals Molecular water-oxidation catalysts for photoelectrochemical cells

2009 ◽  
pp. 9374 ◽  
Author(s):  
Robin Brimblecombe ◽  
G. Charles Dismukes ◽  
Gerhard F. Swiegers ◽  
Leone Spiccia
Keyword(s):  
Water Oxidation ◽  
Photoelectrochemical Cells ◽  
Molecular Water ◽  
Oxidation Catalysts

scholarly journals Rational Design Rules for Molecular Water Oxidation Catalysts based on Scaling Relationships

2017 ◽  
Vol 23 (65) ◽  
pp. 16413-16418 ◽  
Author(s):  
Joeri Hessels ◽  
Remko J. Detz ◽  
Marc T. M. Koper ◽  
Joost N. H. Reek
Keyword(s):  
Water Oxidation ◽  
Rational Design ◽  
Molecular Water ◽  
Oxidation Catalysts ◽  
Design Rules ◽  
Scaling Relationships

Highly efficient and robust molecular water oxidation catalysts based on ruthenium complexes

2014 ◽  
Vol 50 (85) ◽  
pp. 12947-12950 ◽  
Author(s):  
Lei Wang ◽  
Lele Duan ◽  
Ying Wang ◽  
Mårten S. G. Ahlquist ◽  
Licheng Sun
Keyword(s):  
Catalytic Activity ◽  
Dicarboxylic Acid ◽  
Water Oxidation ◽  
Ruthenium Complexes ◽  
Molecular Water ◽  
Oxidation Catalysts ◽  
Turnover Number ◽  
High Turnover ◽  
Molecular Catalyst ◽  
Highly Efficient

The molecular catalyst Ru(bda)L2 (H2bda = 2,2′-bipyridine-6,6′-dicarboxylic acid, L = 6-bromophthalazine) shows excellent catalytic activity for water oxidation. By using Ce(NH4)2(NO3)6 as an oxidant, the catalyst reached a high turnover number TON = 100 000 in 3 hours.

scholarly journals On the Stability of Water Oxidation Catalysts: Challenges and Prospects

2012 ◽  
Vol 65 (6) ◽  
pp. 638 ◽  
Author(s):  
Alex Izgorodin ◽  
Orawan Winther-Jensen ◽  
Douglas R. MacFarlane
Keyword(s):  
Water Splitting ◽  
Water Oxidation ◽  
Commercial Application ◽  
Significant Progress ◽  
Oxidation Catalysts ◽  
Research Focus ◽  
Catalytic Activities ◽  
The Stability ◽  
Stability Of Water

Future requirements for water splitting technologies need highly efficient water oxidation catalysts that are sufficiently stable for operation over many years. Recent research has achieved significant progress in improving the electro-catalytic activities of these catalysts. However, there has not been a strong research focus on their long-term mechanical and chemical stability, yet this is critical for commercial application. In this paper we discuss some of the chemical and thermodynamic challenges confronting this goal, as well as some of the strategies that are available to overcome them. The challenge becomes even greater in the area of photo-active electromaterials; fortunately some of the same strategies may allow progress in this area also.

Molecular Water Oxidation Catalysts from Iron

2014 ◽  
pp. 153-162 ◽  
Author(s):  
W. Chadwick Ellis ◽  
Neal D. McDaniel ◽  
Stefan Bernhard
Keyword(s):  
Water Oxidation ◽  
Molecular Water ◽  
Oxidation Catalysts

scholarly journals Dye-sensitized photoelectrochemical water oxidation through a buried junction

2018 ◽  
Vol 115 (27) ◽  
pp. 6946-6951 ◽  
Author(s):  
Pengtao Xu ◽  
Tian Huang ◽  
Jianbin Huang ◽  
Yun Yan ◽  
Thomas E. Mallouk
Keyword(s):  
Solar Cell ◽  
Water Splitting ◽  
Water Oxidation ◽  
Molecular Water ◽  
Phosphate Solution ◽  
Oxidation Catalysts ◽  
Faradaic Efficiency ◽  
Dye Sensitized ◽  
Electrode Potentials ◽  
Oxide Electrodes

Water oxidation has long been a challenge in artificial photosynthetic devices that convert solar energy into fuels. Water-splitting dye-sensitized photoelectrochemical cells (WS-DSPECs) provide a modular approach for integrating light-harvesting molecules with water-oxidation catalysts on metal-oxide electrodes. Despite recent progress in improving the efficiency of these devices by introducing good molecular water-oxidation catalysts, WS-DSPECs have poor stability, owing to the oxidation of molecular components at very positive electrode potentials. Here we demonstrate that a solid-state dye-sensitized solar cell (ss-DSSC) can be used as a buried junction for stable photoelectrochemical water splitting. A thin protecting layer of TiO2 grown by atomic layer deposition (ALD) stabilizes the operation of the photoanode in aqueous solution, although as a solar cell there is a performance loss due to increased series resistance after the coating. With an electrodeposited iridium oxide layer, a photocurrent density of 1.43 mA cm−2 was observed in 0.1 M pH 6.7 phosphate solution at 1.23 V versus reversible hydrogen electrode, with good stability over 1 h. We measured an incident photon-to-current efficiency of 22% at 540 nm and a Faradaic efficiency of 43% for oxygen evolution. While the potential profile of the catalyst layer suggested otherwise, we confirmed the formation of a buried junction in the as-prepared photoelectrode. The buried junction design of ss-DSSs adds to our understanding of semiconductor–electrocatalyst junction behaviors in the presence of a poor semiconducting material.

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