Surface electric field driven directional charge separation on Ta3N5 cuboids Chock enhancing photocatalytic solar energy conversion

Enhancing the separation and transfer of photogenerated carriers is critical factor for increasing the light to chemical energy conversion efficiencies. Here, we exposed {001} and {010} facets on [100] oriented Ta3N5 cuboid, creating 18.6 times enhancement in photocatalytic reduction of CO2 to CH4 and a 0.42 V-RHE (reference to reversible hydrogen electrode) photocurrent onset potential for photoelectrochemical water splitting. The pronounced photocatalytic performance is mainly attributed to that surface electric field from large surface band bending of the {001} with high work function drives electrons and holes to {010} and {001}, respectively, achieving a spatial charge separation. Differing to a main effect in charge separation and transfer for the traditional junction electric field region at buried heterjunction or homojunction interface, a surface electric field region is a place where charges separate and transfer efficiently and also the place for the catalytic reactions to occur.