Photoelectrochemical production of hydrogen from wastewater

A system comprising:

• a reaction chamber that contains an electrolyte solution, wherein the electrolyte solution comprises an aqueous fluid having wastewater at least partially dissolved therein;
• a photocathode at least partially immersed in the electrolyte solution, wherein the photocathode is capable of generating electron-electron hole pairs upon exposure to light, and wherein the photocathode comprises a silicon-based heterojunction;
• and
• a photocatalyst at least partially immersed in the electrolyte solution, wherein the photocatalyst is electrically connected to the photocathode, wherein the photocatalyst comprises a semiconductor, and wherein the photocatalyst is capable of generating electron-electron hole pairs upon exposure to light.

A method of fabricating a silicon-based heterojunction, the method comprising:

• etching, by electrodeless chemical process, micro-pyramid arrays in both sides of an n-type silicon wafer;
• forming a p+ emitter layer onto a face of the n-type silicon wafer by thermal diffusion;
• forming an n+ back surface field layer onto an opposing face of the n-type silicon wafer by thermal diffusion;
• depositing, on top of the p+ emitter layer, an Al2O3 layer by atomic layer deposition;
• depositing, on top of the Al2O3 layer, an Si3N4 layer by plasma-enhancer chemical vapor deposition;
• etching the Al2O3 layer and the Si3N4 layers with a patterned mask;
• and
• depositing a silver (Ag) layer on top of the Si3N4 layer.