Ni‐Nanocluster Modified Black TiO₂ with Dual Active Sites for Selective Photocatalytic CO₂ Reduction

Abstract

One of the key challenges in artificial photosynthesis is to design a photocatalyst that can bind and activate the CO molecule with the smallest possible activation energy and produce selective hydrocarbon products. In this contribution, a combined experimental and computational study on Ni-nanocluster loaded black TiO (Ni/TiO ) with built-in dual active sites for selective photocatalytic CO conversion is reported. The findings reveal that the synergistic effects of deliberately induced Ni nanoclusters and oxygen vacancies provide (1) energetically stable CO binding sites with the lowest activation energy (0.08 eV), (2) highly reactive sites, (3) a fast electron transfer pathway, and (4) enhanced light harvesting by lowering the bandgap. The Ni/TiO photocatalyst has demonstrated highly selective and enhanced photocatalytic activity of more than 18 times higher solar fuel production than the commercial TiO (P-25). An insight into the mechanisms of interfacial charge transfer and product formation is explored.

Photocatalytic CO2 Reduction to C2+ Products

“…In this case, experimental data shows that the product selectivity decreased, obtaining CH3CHO and CH3OH mixtures. Therefore, the observed selectivity towards CH3CHO is proposed to be a consequence of the dual CO2 adsorption giving rise to CO and O fragments on Ni and Ti(VO) sites, respectively, during the multistep reaction process 74. Again, this study illustrate the potential of performing theoretical calculations on valid models to rationalize selectivity changes.In a different approach, quantum size WO3•0.33H2O nanotubes with large surface VO sites have been reported to produce photocatalytic CO2 reduction to CH3COOH (8e -+ 8H + ) under solar light with 85 % selectivity.76 The WO3•0.33H2O nanotubes were synthetized by oleate-assisted hydrothermal synthesis.76 The oleate ions appear to be responsible for the formation of a high VO concentration, since samples prepared in the absence of oleate presented much lower VO…”

“…In similar approach, Ni-nanoclusters deposited on black TiO2 demonstrated high selectivity towards CH3CHO (10 e -+ 10 H + ) in the photocatalytic CO2 reduction. 74 As the previously commented reduction by NaBH4, TiO2 hydrogenation promotes TiO2 bandgap narrowing due to the generation of VO and Ti 3+ defetcts. 75…”

Polydopamine and Barbituric Acid Co‐Modified Carbon Nitride Nanospheres for Highly Active and Selective Photocatalytic CO2 Reduction

“…Since Inoue and Fujishima first reported photocatalytic reduction of CO 2 into valuable organic compounds (HCOOH, CH 3 OH, HCHO, and CH 4 ) in the presence of semiconductor photocatalyst in aqueous solution, there has been great interest in investigating stable and efficient semiconducting oxide photocatalysts with appropriate redox potential for photochemical reduction of CO 2 , . Various oxide semiconductors, such as TiO 2, , ZnO,, SnO 2 , Bi 2 WO 6 , ZrO 2 , Ga 2 O 3 , InTaO 4 and Zn 2 GeO 4 , have been developed and applied in photocatalytic reduction of CO 2 and exhibited reasonable photocatalytic performance. However, these photocatalysts either only work under UV‐light or consist of scare metal which limit their large‐scale applications.…”

Defective TiO2 for photocatalytic CO2 conversion to fuels and chemicals

“…Hydrogenation using H 2 atmosphere was also beneficial to reduce metal ions into metals along with the generation of oxygen vacancies and Ti 3+ in TiO 2 . Billo et al 53 introduced dual active sites, Ni nanocluster and the oxygen vacancies for the enhanced CO 2 conversion. For this, Ni nanocluster supported oxygen-deficient black TiO 2 was synthesized via the one-pot hydrothermal process, followed by hydrogenation under pure H 2 gas flow at 300 °C for 3 h. The sample before and after hydrogenation was referred to as Ni/TiO 2 and Ni/TiO 2 [V O ], respectively.…”