Enhanced oxidation power in photoelectrocatalysis based on a micrometer-localized positive potential in a terrace hetero p–n junction

Abstract

Generally, p-n junction-based solar energy conversion has the disadvantage of a loss in potential gain in comparison with the photon energy. In this study, we found a more positive potential for a lateral domain interface of p-n junction than for a conventional p-n junction. A terrace bilayer (TB) p-n junction of phthalocyanine (H 2 Pc) and 3,4,9,10perylenetetracarboxylic-bis-benzimidazole (PTCBI) was studied using scanning Kelvin probe microscopy (SKPM), and its electronic properties were analyzed using the contact potential difference (V CPD) data. The analysis of V CPD in the single layer region and the bilayer region (BLR) indicated a vacuum level shift through the electron transfer from PTCBI into indium tin oxide (ITO), from H 2 Pc into ITO and from H 2 Pc into PTCBI. Furthermore, the comparison of these V CPD data indicated a micrometer-localized positive potential in the boundary region (BDR) of the terrace bilayer structure of ptype on n-type. The gain difference of the V CPD reached +0.1 V in comparison with the BLR. The phenomena can be explained as a lateral dipole at the p-n junction. Similar phenomena were observed in TB-H 2 Pc/C 60 /ITO and TB-H 2 Pc/ PTCBI/Au. The gain was extracted as oxidation power in photoelectrochemistry; i.e., at −0.2 V vs. Ag/AgCl a greater anodic current was observed for a patterned terrace bilayer electrode. Additionally, as a photocatalyst film (i.e., a H 2 Pc (dot)/PTCBI/PTFE membrane filter), the p-n dot terrace structure showed a higher quantum efficiency (5.1%) than that of the bilayer (3.2%) for the decomposition of acetic acid. The present design and method were utilized to obtain an efficient photocatalyst, especially through the mitigation of potential loss from the photon energy to redox powers without changing the molecular component.

Tunable Photo‐Electrochemistry of Patterned TiO2/BDD Heterojunctions

“…Both contributions effectively increase the separation and transportation of the photoexcited charge carriers (Figure 6C). [ 56,57 ] As a result of such a lateral polarization, the photocurrent enhancement of a patterned TiO 2 /BDD composite film (or heterojunction) is more remarkable than that of a TiO 2 film that is coated on a BDD film (or a conventional heterojunction), even when the same bias potential is applied (Figure 3C). To summarize, such a patterned TiO 2 /BDD composite film (or heterojunction) combines the features of a BDD UMEA, a TiO 2 /BDD p–n junction and fast charge separation in a lateral direction, resulting in the significant enhancement of its PEC performance.…”

π-Extended Poly(benzimidazoanthradiisoquinolinedione) Ladder-type Conjugated Polymer

“…From the cyclic voltammogram (CV) (Figure d), the onset of the first reduction of Cl 4 –PTCBI occurred at −0.07 V (vs Fc/Fc + , HOMO = −4.8 eV), corresponding to an extremely low LUMO value of −4.73 eV. This is not surprising since the LUMO value of unchlorinated PTCBI was reported to be as low as −4.3 to −4.5 eV . The onset of the first reduction for Cl4-BAL occurred at +0.03 V (vs Fc/Fc + ), corresponding to an even lower LUMO value of −4.83 eV.…”

Recent Developments in the Use of Heterogeneous Semiconductor Photocatalyst Based Materials for a Visible-Light-Induced Water-Splitting System—A Brief Review

“…The utilization of longer wavelength reaching to near-infrared is also attractive to utilize the sunlight [48,199]. Very recently, lateral charge separation to the substrate direction was discovered for step shape electrode using Kelvin probe force microscopy [200]. It is noteworthy that phthalocyanine has another role as a catalyst.…”