This project aims to produce advanced materials for a variety of important industrial applications via the controlled decomposition of designer single-source precursor molecules. The project has involved three primary goals: (1) Synthesis of new precursors: This effort is focused on new main group element (E) and transition metal (M)  cluster compounds that possess E:M ratios not already present in the literature but that would be expected to decompose to E_xM_y solid state materials with known important properties. (2) Production of thin films: The precursors reported in (1) are converted to phase pure materials. (3) Catalytic testing: We have partnered with the research group of Professor Jiming Bao at the University of Houston to test the thin film materials made in this project towards the water splitting reaction, which has tremendous application in the energy industry for the production of hydrogren as a fuel source.

A summary of significant results from these three aims follows:

Aim 1:  A number of new compounds have been prepared and characterized that fall into five broad classifications based on elemental composition, with compounds containing (1) iron and phosphorus, (2) iron, manganese and phosphorus, (3) iron and arsenic, (4) iron, manganese and arsenic, and (5) iron, manganese, phosphorus and arsenic. The latter composition is a particularly important goal because compounds containing Fe, Mn, P and As have been shown to have a very high magnetocaloric effect, which is important in the production of magnetic refrigeration devices and energy production. Twelve of these compounds have been reported in three publications chemical journals (J. Organomet. Chem. 2017, Ahead of Print; Organometallics 2016, 35, 471-483; Inorg. Chem. 2016, 55, 6679-6684). Several additional compounds have been prepared and their synthesis and characterization is being finished and will soon be published.

Aim 2: In preparing new film materials, we have targeted preparation of new phase pure materials, in particular thin films, that have not been previously reported, especially those that possess more than one type of transition metal or main group element. One study built on our production of pure Fe₃P films in the previous NSF grant by codecomposition of the Fe-P precursor with a suitable Co-P or Fe-Te precursors to prepare Fe_3-xCo_xP or Fe₃P_1-xTe_x, respectively. This work on has been published (Chem. Mater 2016, 28, 7088-71). An different approach is to build the different elements into the same precursor and this project was also successful, leading for the first time to phase pure films of FeMnP in a metastable crystalline form (Chem. - Eur. J. 2017, 23, 5565-5572). In work that is being written up for publication, we have prepared phase pure films of FeP and Fe₂P. Our current efforts are extending these studies to produce films that contain Co or Ni in addition to Fe and/or Mn. Of particular significance is our ability to produce these films on a wide variety of substrates, including semiconductors, which has led to a particularly noteworthy application as described in Aim 3. One paper has also appeared that reports the completion of a project started under the prior NSF grant in which we have shown that we can coat Fe₂P nanoparticles with a gold shell to produce photonic materials in collaboration with the research group of Professor Naomi Halas (RSC Adv. 2017, 7, 25848-25854).

Aim 3: In collaboration with the research group of Professor Jiming Bao at the University of Houston, we have examined the catalytic activity of our films towards the water splitting reaction that produces H₂ and O₂. FeMnP films have been deposited on TiO₂, the first time a metal phosphide film has been prepared on a semiconductor. This achievement has allowed us to perform the photo-electrocatalytic production of oxygen evolution reaction using sunlight (ACS Nano 2017, 11, 4051-4059). This report was featured on the Science360.gov website as a "top story". In related work, we deposited phase pure FeMnP films on nickel foam and graphene-coated nickel foam. That material has proven highly efficient at electrocatalysis for the total water splitting reaction (Nano Energy 2017, 39, 444-453). This report was also picked up by Science360.gov and the DOE website as a "University Research Highlight). These successes have been particularly gratifying. In more recent work, we have examined the water splitting catalytic activity of Fe₃P, Fe₂P an FeP thin films. Fe₃P is the most active of these and a manuscript describing this work is in preparation. Heterometallic phosphide compounds have proven particularly effective for water splitting catalysis and are being actively studied.

Last Modified: 09/01/2017
Modified by: Kenton H Whitmire