Bimetallic CuCo nanoparticles optimized hydrogen generation active centers thereby significantly enhancing TiO2 photocatalytic activity

Bimetallic nanostructures are currently a hot pot material among many hydrogen generation co-catalysts. In this study, CuCo bimetallic nanostructures were formed by introducing Co into Cu as the co-catalyst for TiO2. Characterization results from XRD, XPS, and TEM indicated the successful preparation of the high-crystallinity, impurity-free CuCo/TiO2 photocatalyst, with CuCo bimetallic nanoparticles uniformly dispersed on TiO2. After the addition of Co, density functional theory (DFT) calculations showed that the free energy of H adsorption on the Cu site was optimized from 0.27 eV to −0.56 eV, which was beneficial for hydrogen production from TiO2. Electrochemical characterization, photoluminescence (PL) spectroscopy, infrared (IR) thermography, and finite difference in time domain (FDTD) results showed that the bimetallic CuCo acted as the co-catalyst, which increased the temperature of the reaction system, facilitated the separation of light-generated electron-hole pairs, and accelerated the charge transfer, thus promoting the photocatalytic hydrogen generation. The findings of the photocatalytic performance demonstrate that the photocatalyst exhibits the H2 generation rate of 1933.8 μmol/g/h, which is approximately 9 times greater than that of pure TiO2 (213.4 μmol/g/h), when the bimetallic CuCo is loaded in the molar ratio of 5:5 and at the loading amount of 2 wt%. Additionally, the photocatalyst demonstrated excellent catalytic stability, reaching 87.1% of the initial after 16 h of cycling tests. It is foreseen that further study and optimization of various metal couplings may enable the larger widespread application of bimetals as co-catalysts for hydrogen generation.