Electron acceleration and capture device for preserving excess kinetic energy to drive electrochemical reduction reactions

A photocathode for producing hydrogen gas and hydrogen containing compounds from reactants within a liquid and supporting electrolytes which reduces the overpotential required to drive the reactions, the semiconductor photocathode comprising:

• an electrical contact that collects carriers;
• a semiconducting region having a first total polarization vector P1, and being operatively associated with the contact;
• a light absorption region adapted to create electron-hole pairs, the light absorption region being adjacent to the semiconducting region, forming a first interface with the semiconducting region, and having a second total polarization vector P2 greater than or equal to P1;
• an electron acceleration region adjacent to the light absorption region, the electron acceleration region having an electron acceleration region bandgap, the electron acceleration region forming a second interface with the light absorption region, the electron acceleration region having a third total polarization vector P3 greater than the second total polarization vector P2 such that a negative polarization charge is formed at the second interface which creates an electric field that is adapted to accelerate electrons within the electron acceleration region away from the second interface;
• and
• an energy capture region having a fourth total polarization vector P4 adjacent to the electron acceleration region, the energy capture region forming a third interface with the electron acceleration region and having an energy capture region bandgap that is larger than the electron acceleration region bandgap such that the potential energy of the conduction band of the energy capture region is larger than the potential energy of the conduction band of the electron acceleration region, the interface charge at the third interface and the space charge in the energy capture region configured to form a junction between the liquid and the energy capture region that depletes the energy capture region of majority carriers such that the resulting electric field in the energy capture region directs electrons in the energy capture region toward the liquid;
• whereby the photocathode is configured such that kinetic energy gained by the electrons in the electron acceleration region is captured as potential energy in the energy capture region so as to facilitate chemical reduction reactions.