Electron Transfer of the Metal/Semiconductor System in Photocatalysis

Abstract

Probing into the relationship between charge carrier dynamics and photocatalytic reactions is central to the understanding and therefore the design of photocatalysts. We have studied the charge carrier lifetime of Pt/C3N4 and compared it to that of C3N4 alone using femtosecond pump–probe transient absorption spectroscopy in the 500–900 nm signal range. Parallel photocatalytic reactions were also conducted to link the extracted lifetime to the corresponding rates of hydrogen production from water. The presence of Pt (with a mean particle size of ca. 2.5 nm) on C3N4 decreased the lifetime of excited electrons in the conduction band (CB). This has occurred in pure water as well as in the presence of the organic sacrificial agent used. These results suggest that Pt particles on this n-type semiconductor act as electron trap centers (either by pumping away CB electrons or by creating trap centers at the interface). The corresponding increase in reaction rates can be linked to this electron transfer.

Photocatalytic Hydrogen Evolution under Ambient Conditions on Polymeric Carbon Nitride/Donor‐π‐Acceptor Organic Molecule Heterostructures

“…In general, the PCN/TBT/Pt complex displays a significantly lower PL signal, faster PL decay rate and enhanced electron transfer efficiency than that of PCN/Pt, indicating highly efficient charge transfer between PCN/TBT and Pt. [ 38–44 ]…”

“…In general, the PCN/TBT/Pt complex displays a significantly lower PL signal, faster PL decay rate and enhanced electron transfer efficiency than that of PCN/Pt, indicating highly efficient charge transfer between PCN/TBT and Pt. [38][39][40][41][42][43][44] To further characterize charge transfer efficiencies, transient photocurrent response and electrochemical impedance spectra (EIS) of the as-prepared electrodes were measured. All PCN/OMs electrodes exhibit higher photocurrent densities than that of PCN ( Figure S30a, Supporting Information).…”

Electron Accumulation Induces Efficiency Bottleneck for Hydrogen Production in Carbon Nitride Photocatalysts

“…Similar electron absorption in the UV-Vis region has also been previously assigned for the melonbased CN x with amine terminations. 12,26,41 Comparison of the decay kinetics in PIA I and PIA II region shows that the decay kinetics in the PIA II region are significantly faster than the PIA I region (Figure 2c). Detailed kinetic analysis indicates that the PIA II is contributed from the superposition of the above-mentioned electron signals and a faster decay component, with a half-life ~ 4 ps at 73 µJ/cm 2 (See Note S2 and Figure S8).…”

Photo-catalytic hydrogen production over Au/g-C3N4: effect of gold particle dispersion and morphology

“…While we do not know this number, a 10 nm length is within the expected numbers for wide band gap semiconductors. 76 It appears that while one needs Au particles to trap electrons, too many of them results in a competition with each other which may then decrease their collective performance. It is worth noting that similar observations have been made by others [77][78][79] and a few interpretations were given; in addition to competition for electrons, increasing of surface defects at the interface of the metal and support, and increasing light scattering were also invoked as possible reasons for the nonlinear behavior.…”