Photoelectrochemical Reaction in an Electric Cell with a Porous Carbon Anode

A photoelectrochemical cell utilizing porous carbon derived from Binchotan charcoal as the anode is demonstrated. Visible pulse laser irradiation of the Binchotan charcoal anode induces the ablation of carbon cations into NaNO3 aqueous solution. Electrons remaining in the anode reduce the potential of the anode with respect to a platinum cathode. As the electrodes are short-circuited, photogenerated electrons are transported from the anode to the cathode as a diffusion current. The photoinduced charge density at the anode exhibits superlinear and linear excitation laser power density dependences at low and high laser power densities, respectively. This difference in excitation power dependence is caused by the valences of the carbon cations generated by absorbing two-photon energy. The revealed reaction mechanism for electron generation at the Binchotan charcoal anode in the photoelectrochemical cell suggests that the sacrificial reagent for the anode can be not only Binchotan charcoal but also any material capable of being ionized by laser ablation. In particular, porous materials that easily ablates cations are a promising sacrificial reagent for the anode of the photoelectrochemical cell.