Progress, Challenge, and Perspective of Bimetallic TiO₂-Based Photocatalysts

Table 1

Recent publications of TiO₂ photocatalysts modified bimetallic nanoparticles used in reduction processes.

Bimetallic NPs	Range particle size [nm]	Irradiation source	Degradation effect and comments	Reference
Au-Pd alloy	n.m.; 32 nm-anatase	450 W high-pressure mercury lamp	The amount of H2O2 obtained on Au-Pd/TiO2 film (44.0 𝜇M) in 60 min was about 3 times higher than on pristine TiO2 (15.2 𝜇M).	[61]
Au-Pd alloy	Au—5; Pd—7; Au/Pd—3 to 5	400 W Xe arc lamp	Pd yielded more than Au in photoreforming, especially at low loadings	[57]
Au-Pd random alloy Au-Pd core (shell) structure	4 to 5	300 W Xe arc lamp	Studying photochemical evolution of H2 from ethanol occurred only from illuminated catalyst. The core/shell structure performed better under Vis, while alloy structure (after calcination) performed better under UV	[32]
Au-Pd alloy Au-Pd-core (shell)	Bimodal size distribution 1 to 8 (Au) and 40 to 70 (Au-Pd)	n.d.	Two types of catalysts were synthesized and investigated. The active catalysts contained relatively large alloy particles with Au core surrounded by a Pd-rich shell. The photocatalytic activity was not studied	[60]
Au/Pt clusters	32	n.d.	Oxygen vacancies produced by electron irradiation stimulated the growth of Au crystals, while the nucleation behavior of Pt was less affected	[76]
Au-Pt structure not identified	<2 nm	Medium pressure Hg lamp with a cut-off filter at 𝜆>400 nm	Synergetic effect of Au-Pt/TiO2 NPs under simulated sunlight compared to monometallic Pt-TiO2 and Au-TiO2 was reported. Higher activity of Au0.5-Pt0.5/TiO2 results from interaction between Au and Pt which can induce a decrease in metal-hydrogen bond strength and improve the electron trapping ability of NPs	[58]
Pd-Cu alloy	n.m.	125 W high-pressure mercury lamp	The role of Pd was to split H2 into absorbed Pd–H atoms, which can reduce nitrite to other nitric species, but also reduce the adjacent copper oxides into metal copper. The highest activity was achieved by using Pd-Cu/TiO2 (Pd : Cu = 2 : 1, 3 wt.%) catalyst	[37]
Cu-Ni/TiO2	20 to 40	500 W halogen lamp	The addition of a small amount of Ni onto Cu/TiO2 (10 wt.%, Cu : Ni mass composition of 9 : 1) enhanced the performance of photocatalyst from producing 5.0 cm^3 to 6.1 cm^3 of hydrogen	[65]
Ni-Cu/TiO2	20 to 30	125 W high-pressure mercury lamp	Cu-Ni/TiO2 nanoparticles revealed about 1.2 times and 2.6 times higher photoactivity than bimetallic photocatalysts Pt-Cu/TiO2 and Pd-Cu/TiO2 obtained using the same preparation procedure	[37]
Pt-Ru/TiO2	50 to 100	n.d.	Among the prepared TiO2 supported bimetallic (Pt-Pd/TiO2 and Pt-Ru/TiO2 and Pt-Au/TiO2) nanocatalysts Pt-Ru/TiO2 showed the best overall conversion and selectivity towards geraniol and nerol	[77]
Pt-Ru clusters	Pt—2.3; Ru—2.2; Pt/Ru—2.0	500 W high-pressure mercury lamp	The present platinum/ruthenium systems were much more active than gold/platinum bimetallic clusters in the reaction of hydrogen generation	[29]