Non-crystalline polymeric solids containing high carbon and nitrogen content and (at least) local π-bonding in heptazine (C6N7) structural repeat units have been generally referred to as “carbon nitrides” with local structures described as having graphite-like interlayer or chain stacking and compositions near C3N4. Typically these are produced via slow thermal condensation of smaller molecular precursors. This presentation will compare materials from conventional C3N4 synthetic methods with materials produced via the exothermic decomposition of a reactive molecular precursor, (C3N3)(NHCl)3. In particular, while most chemical, local structural features, and optical properties are similar to reference carbon nitrides, the photocatalytic hydrogen evolution reaction (HER) activity of TCM-derived C3N4 shows differences that may reflect local defects or electron/hole recombination rates, as well as co-catalyst deposition differences. The addition of alkali salts to the TCM precursor modifies its reactivity and product porosity (after byproduct salts are removed). Comparisons of bulk chemical analysis, XPS, optical properties, as well as IR and solid-state NMR will be used to propose changes that occur with C3N4 structures and properties for salt addition reactions. The photocatalytic HER activity of several TCM-derived carbon nitrides with photodeposited co-catalysts will also be presented. Salt-mediated changes in C3N4 surface area may influence its ability to more effectively photoreduce metal co-catalysts on its surface that can impact hydrogen evolution from aqueous solution.

Comparison of structure, properties, and photocatalytic activity of polymeric carbon nitrides synthesized from a reactive trichloromelamine precursor

2019 Spring National Meeting

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