Abstract: The aqueous reaction dynamics of the manganese(II)-functionalised Wells-Dawson polyoxometalate [Mn₄(H₂O)₂(P₂W₁₅O₅₆)₂]^16- has been determined as a function of pH using variable temperature $^{17}$O NMR, and compared with that of the well-studied monomeric manganese(II) hexa-aqua ion, [Mn(H₂O)₆]²⁺. While the rate of aquo-ligand exchange on the hexa-aqua ion remains independent of pH in the range 3.2 -- 6.0, the rate of water exchange of the polyoxometalate ion varies by a factor of fifteen, from 1.98$^.10⁷ s^-1 at pH 3.2 to 1.3^.10⁶ s^-1 at pH 6.0. This decrease in rate of exchange correlates with the deprotonation of the polyoxometalate framework.

Sharma, Rupali; Zhang, Jie;Ohlin, C. André pH-dependent solution dynamics of a manganese(II) polyoxometalate, [Mn₄(H₂O)₂(P₂W₁₅O₅₆)₂]^16-}, and [Mn(H₂O)₆]²⁺ Dalton Trans., 2015, 44, 19068-19071. Link

Abstract: A method has been developed for the efficient electrodeposition of cobalt and nickel nanostructures with the assistance of the Lindqvist ion [Nb₆O₁₉]^8-. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma optical emission spectrometry, and a range of electrochemical techniques have been used to characterize the morphology, composition, catalytic water oxidation activity and stability of the films in alkaline solution. SEM images show that films consisting of nanoparticles with diameters of ca. 30 to 40 nm are formed after 40-50 potential cycles of deposition. Nb and Co/Ni are detected in the films by EDX. ICP-MS results show an elemental ratio of 1:1 for Co:Nb and 1:3 for Ni:Nb, respectively. Raman spectra reveal the presence of both [Nb₆O₁₉]^8- and Co(OH)₂/Ni(OH)₂. The films exhibit excellent stability and efficiency for electrocatalytic water oxidation in alkaline solution. Turnover frequencies of 12.9 and 13.2 s^-1 were determined by rotating ring disk electrode voltammetry at an overpotential of 480 mV for Co and Ni films, respectively. Fourier transformed large amplitude alternating current (FTAC) voltammetry reveals an additional underlying oxidation process for Co under catalytic turnover conditions, which indicates that a CoIV species is involved in the efficient catalytic water oxidation reactions. FTAC voltammetric data also suggest that the Ni films undergoes a clear phase transformation upon aging in aqueous 1 M NaOH and the electrogenerated higher oxidation state Ni from beta-NiOOH is the more active form of the catalyst.

Liu, Yuping; Guo, Si-Xuan; Ding, Liang; Ohlin, C. André; Bond, Alan M.; Zhang, Jie Lindqvist Polyoxoniobate Ion-Assisted Electrodeposition of Cobalt and Nickel Water Oxidation Catalysts ACS Appl. Mater. Interfaces, 2015, 7(30), 16632-16644. Link

Abstract: An organic photo-electrochemical catalyst for the hydrogen evolution reaction (HER) based on the conducting polymer, poly(2,2'-bithiophene) (PBTh), is further explored. Experimental parameters such as substrate type, electrolyte, pH and thickness of the film are explored and their corresponding effects on catalytic behaviour and performance discussed. Significant findings include the four-fold increase in performance by the reduction of thickness to better facilitate charge mobility and the successful photo-catalysis of the HER at pH 11, with an onset that is 0.15 V below E0. Faradaic efficiency of the catalyst is also determined with a maximum recorded efficiency of 80% despite known losses such as crossover reactions and H2 escape from within the system. Long-term stability testing shows the successful operation of the film over a period of 10 days.

Ng, Chun H.;[1] Winther-Jensen, Orawan;[1] Ohlin, C. André;[2] Winther-Jensen, Bjorn[1] Exploration and optimisation of poly(2,2'-bithiophene) as a photo-electrocatalyst for hydrogen production J. Mat. Chem A, 2015, 3, 11358-11366 Link

1. Department of Materials Engineering, Monash University, Vic., Australia
2. School of Chemistry, Monash University, Vic., Australia

Abstract: Reversible interaction with carbon monoxide results in the onset of dynamic atropisomerism at 298 K in an otherwise static NHC-based rhodium pincer complex, [Rh(C^N^C-(CH₂)₁₂)(CO)][BAr^F4 ] (1, Ar^F= 3,5- C₆H₃(CF₃)₂). The mechanism of this process has been comprehensively interrogated by a combination of variable temperature NMR spectroscopy, IR spectroscopy, and computational modeling. In addition, a structural analogue of a high-energy symmetrical intermediate species -- invoked in the process but not directly observed spectroscopically -- has been prepared and characterised in solution and the solid-state.

Andrew, Rhiann E.;[1] Ferdani, Dominic W.;[1] Ohlin, C. André;[2] Chaplin, Adrian B.[1] Coordination Induced Atropisomerism in a NHC-based Rhodium Macrocycle Organometallics, 2015, 34(5), 913-917. Link

1. Department of Chemistry, University of Warwick, UK
2. School of Chemistry, Monash University, Vic., Australia

Abstract: A series of commercially available dyes were characterised by electrochemical, spectroscopic and computational methods. Several dyes, including Fuchsin Basic and Malachite Green were found to have properties that make them potential candidates for use in photo-electrochemical systems. The risks of combining different characterisation methods are also highlighted, namely the combination of thermodynamic reactions (electrochemical redox reactions), electronic transitions (optical spectroscopy) and the use of computational techniques to describe them.

Ng, Chun H.;[1] Ohlin, C. André;[2] Winther-Jensen, Bjørn[1] Characterisation of a series of triarylmethane dyes as light harvesters for photo-electrochemical systems Dyes and Pigments, 2015, 115, 96-101. Link

1. Department of Materials Engineering, Monash University, Vic., Australia
2. School of Chemistry, Monash University, Vic., Australia

Abstract: N/A.

Perera, Ishanie R.;[1] Daeneke, Torben;[2] Makuta, Satoshi;[5] Yu, Ze;[3] Tachibana, Yasuhiro;[5,6] Mishra, Amaresh;[7] Bäuerle, Peter;[7] Ohlin, C. André;[1] Bach, Udo;[2,3,4] Spiccia, Leone[1] Application of the Tris(acetylacetonato)iron(II)/(III) Redox Couple in p-type Dye Sensitized Solar Cells Angew. Chem. Int. Ed., 2015, 54(12), 3758-3762. Link

1. School of Chemistry, Monash University, Vic., Australia
2. CSIRO Materials Science and Engineering, CSIRO, Vic., Australia
3. Department of Materials Engineering, Monash University, Vic., Australia
4. Tech. Fellow, Melbourne Centre for Nanofabrication, Vic., Australia
5. School of Aerospace, Mechanical and Manufacturing Engineering, RMIT University, Vic., Australia
6. Japan Science and Technology Agency (JST), Saitama, Japan
7. Institute for Organic Chemistry II and Advanced Materials, University of Ulm, Germany