Optimized TiO2/CuxO/C nanocomposites derived from bi-MOF NH2-MIL-125(Ti/Cu) with in situ formed p–n heterojunctions exhibited superior photocatalytic HER performance without noble metals.

No abstract

Surface-functionalized nitrogen/carbon co-doped polymorphic TiO 2 phase junction nanoparticles uniformly distributed in porous carbon matrix were synthesized by a simple one-step pyrolysis of titanium based metal-organic framework (MOF), NH 2 -MIL-125(Ti) at 700°C under water vapour atmosphere. Introducing water vapour during the pyrolysis of NH 2 -MIL-125(Ti) not only functionalizes the derived porous carbon matrix with carboxyl groups but also forms additional oxygen-rich N like interstitial/intraband states lying above the valence band of TiO 2 along with the self-doped carbon, which further narrows the energy band gaps of polymorphic TiO 2 nanoparticles that enhance photocatalytic charge transfer efficiency. Without co-catalyst, sample N-C-TiO 2 /C ArW demonstrates H 2 evolution activity of 426 mmol g cat -1 h À1 , which remarkably outperforms commercial TiO 2 (P-25) and N-C-TiO 2 /C Ar with a 5-fold and 3-fold H 2 generation, respectively. This study clearly shows that water vapour atmosphere during the pyrolysis increases the hydrophilicity of the Ti-MOF derived composites by functionalizing porous carbon matrix with carboxylic groups, as well as enhancing the electrical conductivity and charge transfer efficiency due to the formation of additional localized oxygen-rich N like interstitial/intraband states. This work also demonstrates that by optimizing the anatase-rutile phase composition of the TiO 2 polymorphs, tuning the energy band gaps by N/C co-doping and functionalizing the porous carbon matrix in the N-C-TiO 2 / C nanocomposites, the photocatalytic H 2 generation activity can be further enhanced.