Lee Joo-Won, Cho Ki-Hyun, Yoon Joon-Soo, Sung Yun-Mo
Department of Materials Science & Engineering, Korea University, Anam-ro 145, Seongbuk-gu, Seoul 02841, Republic of Korea.
Nanoscale. 2020 Apr 21;12(15):8525-8535. doi: 10.1039/d0nr00477d. Epub 2020 Apr 3.
We, for the first time, report the development of infrared (IR)-driven photoelectrochemical (PEC) cells using up-conversion glass-ceramics as substrates, which is different from the previous strategies of decorating photocatalysts with up-conversion (UC) rare earth-doped fluoride nanoparticles to utilize IR light. Our approach is more efficient since the use of UC glass-ceramics as substrates of photocatalysts could overcome the chemical instability of fluoride nanoparticles, the blockage of incident light, and the limited exposure of photocatalysts to liquid electrolytes. Oxyfluoride glass-ceramics bearing (Yb,Er)-doped YF and (Yb,Tm)-doped YF nanocrystals turned out to generate UC green and ultraviolet/blue emissions, respectively, under 980 nm illumination. High-density ZnO nanorods were grown on the up-conversion glass-ceramic substrates by the hydrothermal method and they were subsequently overcoated with CdSe nanocrystals to obtain CdSe/ZnO heterostructures by the chemical bath deposition method. CdSe nanoparticles were excited by both the UC UV emission from Tm and the visible emission from Er and Tm, while ZnO nanorods were excited mostly by the UC UV emission from Tm. Because of the difference in the UC emissions from Er and Tm, two distinct carrier transportations, sensitization and type-II cascade, occurred in the identical CdSe/ZnO heterostructures. Eventually, CdSe/ZnO fabricated on the glass-ceramics bearing (Yb,Tm)-doped YF showed increased photocurrent density compared to that fabricated on the glass-ceramics bearing (Yb,Er)-doped YF due to the charge separation activated by the type-II cascade structure.
我们首次报道了以红外（IR）驱动的光化学电池（PEC）的发展，该电池以上转换微晶玻璃为基底，这与之前用掺杂稀土的上转换（UC）氟化物纳米颗粒修饰光催化剂以利用红外光的策略不同。我们的方法更高效，因为使用上转换微晶玻璃作为光催化剂的基底可以克服氟化物纳米颗粒的化学不稳定性、入射光的阻挡以及光催化剂与液体电解质接触受限的问题。含（Yb,Er）掺杂YF和（Yb,Tm）掺杂YF纳米晶体的氟氧化物微晶玻璃在980nm光照下分别产生上转换绿色和紫外/蓝色发射。通过水热法在这些上转换微晶玻璃基底上生长高密度的ZnO纳米棒，随后通过化学浴沉积法在其上包覆CdSe纳米晶体以获得CdSe/ZnO异质结构。CdSe纳米颗粒可被Tm产生的上转换紫外发射以及Er和Tm产生的可见光发射激发，而ZnO纳米棒主要被Tm产生的上转换紫外发射激发。由于Er和Tm产生的上转换发射不同，在相同的CdSe/ZnO异质结构中发生了两种不同的载流子传输，即敏化和II型级联。最终，与在含（Yb,Er）掺杂YF的微晶玻璃上制备的CdSe/ZnO相比，在含（Yb,Tm）掺杂YF的微晶玻璃上制备的CdSe/ZnO由于II型级联结构激活的电荷分离而表现出更高的光电流密度。
