This study describes the UV solution photodeposition of several earth-abundant 3d transition metals (Co, Ni, and Cu) onto the surface of nanoparticulate TiO₂. Irradiated methanolic metal dichloride solutions with suspended Degussa P25-TiO₂ (1–2 wt % metal to TiO₂) yield visibly colored titanias, whereas the bulk TiO₂ structure is unchanged; X-ray photoelectron spectroscopy confirms that metals are present on the titania surface in either reduced metal (Cu/Cu⁺) or metal cation states (Co²⁺ and Ni²⁺), and UV–vis diffuse reflectance spectroscopy shows new visible absorbance features. The analyzed bulk metal contents (∼0.04–0.6 at. %, highest for copper) are lower than the nominal metal solution content. Mixed-metal solution photodeposition reactions roughly parallel observations for single metals, with copper deposition being most favored. These 3d metal surface-modified titanias show significant (∼5–15×) improvement in UV photocatalytic H₂ evolution versus unmodified TiO₂. H₂ evolution rates as high as 85 μmol/h (8500 μmol h^–1 g^–1) were detected for Cu-coated TiO₂ using continuous monitoring of reactor headspace gases by portable mass spectrometry. Control experiments verify the necessity of the methanol sacrificial oxidant in both metal deposition and H₂ evolution. In situ metal surface deposition is quickly followed by enhanced H₂ evolution relative to TiO₂, but at lower levels than isolated metal surface-modified titanias. The photodeposited 3d metal species on the TiO₂ surface likely act to reduce electron–hole recombination by facilitating the transfer of photoinduced TiO₂ conduction band electrons to protons in solution that are reduced to H₂. This study demonstrates a facile method to modify photoactive TiO₂ nanoparticles with inexpensive 3d transition metals to improve photocatalytic hydrogen evolution, and it shows the utility of quantitative real-time gas evolution monitoring by portable mass spectrometry.

There is increasing interest in high surface area carbon nitride materials as potential coordinatively active analogs of amorphous carbon systems. It is generally difficult to produce extended carbon structures with high nitrogen contents. This article describes a facile molecular decomposition process that produces bulk quantities of an amorphous nitrogen-rich carbon nitride material, C₃N_4+x where 0.5 < x < 0.8, in only a few seconds without the use of complex experimental apparatus. The trichloromelamine molecular precursor [(C₃N₃)(NHCl)₃] rapidly decomposes when heated externally above 185 °C or when brought into contact with a heated filament. Morphological studies show that the rapid synthesis process produces a porous, sponge-like material containing spherical nanofeatures (<300 nm). These amorphous carbon nitrides were analyzed by IR, NMR, optical, and X-ray photoelectron spectroscopy, which indicate that the carbon centers have primarily sp² hybridization, triazine (C₃N₃) rings are retained in the product, and nitrogen species bridge triazines. These C₃N_4+x materials are also luminescent in the blue region even after annealing to 400 °C. They exhibit thermal and chemical stability with no significant decomposition until 600 °C or reactivity with concentrated aqueous base.

Solvent-free and template-free synthesis of crystalline zeolites using mechanochemical pre-reactions between Na₂SiO₃ and Al₂(SO₄)₃ forming Na₂SO₄ and well-mixed aluminosilicate intermediates.

Nanocrystalline InN powders have been synthesized through metal azide decomposition in superheated toluene and refluxing hexadecane solvents near 280 °C. The metal azide intermediates were formed in situ through the metathesis reaction of InBr₃ and NaN₃. The InN products from toluene consist of ∼10 nm hexagonal (wurtzite) structured crystallites in aggregated arrangements. InN from hexadecane and lower temperature toluene reactions produced more poorly crystalline InN that appears to contain a cubic (zinc blende) component. Coordinating amine solvents led to decomposition of the nitride to indium metal. Several reactions were undertaken to produce mixed metal nitrides of the form Ga_1−zIn_zN where z is 0.5 and 0.75. The mixed metal nitride products are analytically consistent with composite versus solid-solution formation, however some metal mixing is observed. Data from X-ray diffraction, electron microscopy, thermal analysis, elemental analysis, and several spectroscopic methods are combined to form a consistent picture of the bulk and surface structures for these nanocrystalline InN materials.

Metal borides have long-standing uses due to their desirable chemical and physical properties such as high melting points, hardness, electrical conductivity, and chemical stability. Typical metal boride preparations utilize high-energy and/or slow thermal heating processes. This report details a facile, solvent-free single-step synthesis of several crystalline metal monoborides containing earth-abundant transition metals. Rapid and exothermic self-propagating solid-state metathesis (SSM) reactions between metal halides and MgB₂ form crystalline FeB, CoB, and NiB in seconds without sustained external heating and with high isolated product yields (∼80%). The metal borides are formed using a well-studied MgB₂ precursor and compared to reactions using separate Mg and B reactants, which also produce self-propagating reactions and form crystalline metal borides. These SSM reactions are sufficiently exothermic to theoretically raise reaction temperatures to the boiling point of the MgCl₂ byproduct (1412 °C). The chemically robust monoborides were examined for their ability to perform electrocatalytic water oxidation and reduction. Crystalline CoB and NiB embedded on carbon wax electrodes exhibit moderate and stable bifunctional electrocatalytic water splitting activity, while FeB only shows appreciable hydrogen evolution activity. Analysis of catalyst particles after extended electrocatalytic experiments shows that the bulk crystalline metal borides remain intact during electrochemical water-splitting reactions though surface oxygen species may impact electrocatalytic activity.