Photo-electrolytic catalyst systems and method for hydrogen production from water

Abstract

A photo-electrolytic catalyst system which comprises two materials: (a) a semiconductor material with a non-zero energy gap Eg which, in response to an incident radiation having an energy greater than Eg, generates electron-hole pairs as charge carriers; and (b) a facilitating material in electronic contact with the semiconductor material to facilitate separation of the radiation-generated electrons from the holes to reduce the probability of charge carrier recombinations The catalyst makes use of both majority and minority charge carriers to promote photo-electrolysis reactions for producing hydrogen directly from water or an aqueous electrolyte at higher rates and improved efficiencies.

Description

FIELD OF THE INVENTION This invention provides a photo-electrolytic catalyst system for water splitting to produce hydrogen and oxygen gases. This invention also provides a method of using an improved semiconductor-based photo-electrolytic catalyst to promote solar energy conversion of water or aqueous electrolyte into hydrogen. BACKGROUND OF THE INVENTION A fuel cell converts chemical energy into electrical energy and some thermal energy by means of a chemical reaction between hydrogen-containing fuel and oxygen. As compared to other energy sources, fuel cells provide advantages that include low pollution, high efficiency, high energy density and simple fuel recharge. Fuel cells can be used in electrochemical engines, portable power supplies for various microelectronic and communication devices, standby power supply facilities, power generating systems, etc. Further, fuel cells utilize renewable resources and provide an alternative to burning fossil fuels to generate power. For ...

AI Technical Summary

Benefits of technology

This invention provides simple (non-complicated) but effective photo-electrolytic catalyst systems which comprise two materials: (a) a semiconductor material with a non-zero energy gap Eg which, in response to an incident radiation having an energy greater than Eg, generates electron-hole pairs as charge carriers; and (b) a facilitating material in electronic contact with the semiconductor material to facilitate separation of the radiation-generated electrons from the holes to reduce the probability of charge carrier recombinations. The catalysts make use of both majority and minority charge carriers to promote photo-electrolysis reactions for producing hydrogen at higher rates and improved efficiencies.

The semiconductor material and / or the facilitating material preferably has at least one dimension being smaller than one micron (1 μm) and, further preferably, smaller than or equal to 100 nm. Either or both materials are preferably porous. These two features (small dimensions and high porosity levels) more readily facilitate the separation of the photon-generated electrons and holes and provide larger material-water interface areas where redox reactions occur, leading to more efficient and faster hydrogen production.

Problems solved by technology

This complicated device includes a multiplicity of stacked photoelectric or photovoltaic elements between a substrate and an electrode, a counter-electrode, and an unbiased external circuit.

The above inventions have one or several of the following drawbacks: (1) complicated junctions or multiple-layer structures, (2) insufficient photolytic or photo-electrolytic efficiency, (3) slow hydrogen production rate, (4) involving non-water liquid ingredients (e.g., EDTA, acid, strong base, or other potentially hazardous chemicals), and (5) photo-catalysts with unknown operating mechanisms (hence, the resulting efficiency, yield, and rate can only be improved by trial-and-error and cannot be readily or effectively optimized).

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