Photoelectrochemical tandem cell with bipolar dye-sensitized electrodes for vectorial electron transfer for water splitting

Direct water electrolysis was achieved with a novel monolithic photoelectrochemical cell. Bipolar WO ₃/Pt and dye-sensitized TiO ₂/Pt semiconductor panels, capable of vectorial electron transfer, have been used for water splitting to yield hydrogen and oxygen; light is the only energy input. The hydrogen production efficiency of this tandem cell, based on the short-circuit current, was ∼1.9% and the maximum hydrogen production efficiency was ∼2.5% when 0.2 V positive bias was applied. When a concentrated LiCl aqueous solution was used as an electrolyte, valuable chlorine was obtained instead of oxygen. The maximum yielding efficiency of hydrogen and chlorine was ∼1.8%.