Aqueous Photoelectrochemical CO2 Reduction to CO and Methanol over a Silicon Photocathode Functionalized with a Cobalt Phthalocyanine Molecular Catalyst

Abstract
We report a precious-metal-free molecular catalyst-based photocathode that is active for aqueous CO₂ reduction to CO and methanol. The photoelectrode is composed of cobalt phthalocyanine molecules anchored on graphene oxide which is integrated via a (3-aminopropyl)triethoxysilane linker to p-type silicon protected by a thin film of titanium dioxide. The photocathode reduces CO₂ to CO with high selectivity at potentials as mild as 0 V versus the reversible hydrogen electrode (vs RHE). Methanol production is observed at an onset potential of −0.36 V vs RHE, and reaches a peak turnover frequency of 0.18 s⁻¹. To date, this is the only molecular catalyst-based photoelectrode that is active for the six-electron reduction of CO₂ to methanol. This work puts forth a strategy for interfacing molecular catalysts to p-type semiconductors and demonstrates state-of-the-art performance for photoelectrochemical CO₂ reduction to CO and methanol.

Citation
Shang, B., Rooney, C. L., Gallagher, D. J., Wang, B. T., Krayev, A., Shema, H., Leitner, O., Harmon, N. J., Xiao, L., Sheehan, C., Bottum, S. R., Gross, E., Cahoon, J. F., Mallouk, T. E., & Wang, H. (2022). Aqueous photoelectrochemical co 2 reduction to CO and methanol over a silicon photocathode functionalized with a cobalt phthalocyanine molecular catalyst. Angewandte Chemie, 135(4). https://doi.org/10.1002/ange.202215213