Enhanced Photocatalytic Hydrogen Evolution with TiO₂–TiN Nanoparticle Composites

Abstract

Metal nitrides have potential in energy applications because of their physical and optical properties. Nanoparticle composites of titanium nitride (TiN) and titanium dioxide (TiO2) were investigated for their photocatalytic hydrogen (H2) evolution activity via methanol reformation. Physical mixing of the nanoparticulate TiO2 and TiN was employed to prevent the oxy-nitride formation and particle aggregation observed in thermal preparations. This convenient combination of TiO2 and TiN demonstrated a substantial synergistic effect with enhanced activity (9.4 μmol/h TiO2–TiN vs 1.8 μmol/h TiO2) under combined UV/vis light. Irradiation under only UV light resulted in a similar enhancement factor compared to using combined UV/vis light, demonstrating that the enhanced activity of the composites occurs essentially for UV-driven photocatalysis. No activity/enhancement was observed with only visible light irradiation; however, minor enhancement was observed when switching between UV and UV/vis irradiation, suggesting a contribution from the TiN plasmon. We propose that the plasmonic contribution is dependent on the band gap excitation of TiO2, which reduces the degree of band bending at the TiO2/TiN interface. This promotes the migration of hot electrons from TiN away from the TiO2/TiN interface to be used for H2 evolution.

Broadband Ultrafast Dynamics of Refractory Metals: TiN and ZrN

“…[ 1–9 ] Titanium nitride (TiN), zirconium nitride (ZrN), and other plasmonic nitrides such as hafnium nitride (HfN) and tantalum nitride (TaN) are particularly attractive due to their high melting points that bolster stability at higher ambient temperatures [ 10–12 ] and/or under higher laser irradiation intensities, [ 13–16 ] in addition to their mechanical hardness [ 17,18 ] and complementary metal‐oxide‐semiconductor compatibility. [ 19–21 ] Recent work has demonstrated that TiN shows strong local heating compared to Au, [ 22–24 ] which may be exploited for photothermal therapy, [ 25,26 ] shape‐memory effects, [ 27 ] thermochromic windows, [ 28 ] photoreactions, [ 29–32 ] heat transducers or thermophotovoltaic materials, [ 22,33–37 ] or photodetection. [ 38 ] Implicit in these observations and devices are very different optical responses of metallic nitrides compared to gold—the most similar classical plasmonic material—particularly with regard to the dissipation of heat.…”

Sustainable Nanoplasmon‐Enhanced Photoredox Reactions: Synthesis, Characterization, and Applications

“…[163] Titanium Nitride (TiN): Often considered an alternative to Au, plasmonic TiN nanoparticles are often used in combination with TiO 2 to realize superior photo catalytic activities. [164,165] Naldoni et al synthesized TiO 2 nanowires and supported them alternatively with plasmonic TiN and Au nanoparticles to study their photo catalytic activity for water splitting. [164] Significantly higher photocurrent responses were noted with TiN as compared to Au and the results were attributed to the ability of TiN to absorb in the visible-NIR region, which constitutes most of the solar spectrum.…”

Progress through synergistic effects of heterojunction in nanocatalysts ‐ Review

“…TiN is an inert chemical semiconductor with a direct band gap of ~2.7 eV being sufficiently negative for water reduction to produce hydrogen. [145] The reduction and oxidation catalytic activity greatly enhance by incorporating the TiN structure into the porous graphene. Extensive efforts in combining TiN with graphene have been studied for the design the active composite photocatalysts.…”