Using waste CO2 to produce essential amino acids for humans: An efficient photoelectrochemical route

L-Phenylalanine (L-Phe), an essential amino acid for humans, is widely
used as building blocks. Currently, L-Phe is obtained via biosynthetic
methods including microbial and enzymatic processes, but their tightly
complex feedback regulation and lengthy reaction steps lead to a low
practical yield of L-Phe. Here, we have designed a hierarchical Si-based
photocathode for L-Phe synthesis by photoelectrochemical coupling of waste
CO2 and nitrophenyl ethane, achieving a high yield rate of 37.5
μg·h-1·cm-2 and a remarkable faradaic efficiency of 21.2% at low applied
potential under 1 sun illumination. The hierarchical structure with
CuO-TiO2-C mixtures dispersed in amorphous TiO2 layer/n+p-Si creates an
internal built-in electric field and forms plentiful conducting channels
to efficiently realize the injection of electrons into Cu and Ti sites.
These Cu and Ti sites adsorb and activate the CO2 and nitrophenyl ethane,
respectively, cooperatively facilitating the L-Phe synthesis. This work
introduces an environmentally friendly, and highly efficient approach for
converting solar energy into valuable amino acid products.