Preparation And Photoelectric Chemical Performance Of Molecular Catalyst Modified BiVO₄ Photoanode

The water is oxidized by the solar energy to produce the clean chemical fuel -hydrogen, is widely considered to be an effective way. to reduce the environmental problems caused by fossil fuel combustion and meet the world's growing energy demand. In the artificial photosynthesis system, the water decomposition reaction is a key step in providing protons and electrons,which is a bottleneck restricting solar energy conversion. The main limiting factors affecting the efficiency of solar fuel synthesis include: i) light absorption, ii) charge separation and transport, iii) surface chemical reaction. Therefore, the molecular catalyst can improve the electron charge separation or can act as a hole receptor is an effective means to solve these problems.In this paper,cobalt-cadmium oxide oxidized molecular catalyst with vinyl groups were synthesized from cobalt metal with low cost. The molecular water oxidation catalyst Co4O₄?O2CMe?4?4-vinylpy?4 was electrochemically polymerized on FTO and BiVO₄ films. Remarkable electrochemical current densities of ca.4 mA/cm² of poly-1/FTO were achieved under 1.2 V vs Ag/AgCl. After a long period of electrolysis, the current density is still nearly 2 mA/cm²,showing stability significantly improved with respect to that of the homogeneous system. Faraday efficiency of poly-1/FTO can reach 84.8%. High photocurrent densities of ca.2 mA/cm² for poly-1/BiVO₄ photoanodes were achieved under under an applied potential of 0.62 V vs Ag/AgCl in the three electrode PEC system with Pt as counter electrode, operated in pH 7 phosphate buffer solution ?light intensity 100 mW/cm²?,and the current density was 8 times higher than that of BiVO₄ photoanodes. Faraday efficiency is also increased from 31.4 % to 59.8 %, confirming that the catalyst is indeed excusively used for O2 evolution. The incident photon-electron conversion efficiency ?IPCE? is increased from 5 % to 23 %, and the hole injection efficiency of the photoanodes is increased from 20 % to 80 %. The charge separation efficiency of poly-1/BiVO₄:BiVO₄ is close to 90% at 1.23 V vs RHE.BiVO₄ semiconductor materials were prepared by modified method,and the prepared nano-porous BiVO₄ photoanodes were modified by AuNPs. The plasma effect of AuNPs was used to enhance the photoresponsiveness of the composite electrode. The results show that the photocurrent of the photocatalytic decomposition of AuNPs/BiVO₄ composite electrode is obviously improved compared with that of BiVO₄ without modified, which indicates that the plasma effect of gold can contribute to the charge transfer of BiVO₄ electrode, and the photocatalytic activity of AuNPs/BiVO₄ electrode is better than that of BiVO₄.In this paper, a mercapto group-modified ruthenium-based molecular catalyst was prepared and the AuNPs/BiVO₄ electrode was modified with the catalyst by chemical adsorption between gold nanoparticles and mercapto groups. The photocatalytic oxidation of Rul/AuNPs/BiVO₄ was studied in the presence of 0.62 V vs Ag/AgCl bias. Under the condition of 100mW/cm² illumination, there was no obvious current drop in the test time, and a relatively constant constant current was obtained. The current density was nearly 2 mA/cm²,the value is 4 times higher than that of BiVv4 and 1.5 times higherthan that of AuNPs/BiVO₄.