Photochemical transformation using engineered metal-free hexagonal boron nitride

Abstract

The inventive concepts disclosed relate to the production of green and blue hydrogen from hydrocarbons using visible light (from a laser, lamp or sun) and defect-engineered boron-rich photocatalysts. We demonstrate that the environment of the B atoms in the lattice can be tuned to favor the dehydrogenation of desired hydrocarbons on reaction sites under visible light. In addition to the hydrogen produced in gas form, carbon atoms are captured by the catalyst and form structures of potential higher value for future applications. Further study of the dark carbonaceous product revealed a graphitic aspect of the material. These findings highlight a new functionality of 2D materials for visible light-assisted capture and conversion of hydrocarbons, with great potential for green hydrogen production ― i.e, hydrogen produced from renewable energy and without the release of CO or CO2.

1 . A method for of making carbon structures, the method comprising the steps of: (i) forming a reaction mixture by contacting a heterogeneous catalyst with a hydrocarbon or carbon source in a chamber, and (ii) focusing an excitation laser on the reaction mixture under conditions that result in formation a carbon structure. 
     
     
         2 . The method of  claim 1  wherein, the heterogeneous catalyst at least partially comprises hexagonal boron nitride. 
     
     
         3 . The method of  claim 2 , wherein the hexagonal boron nitride has at least one catalytically active defect on a surface thereof. 
     
     
         4 . The method of  claim 3 , wherein the catalytically active defect is selected from the group consisting of Stone-Wales defects, B/N defects, boron substituted nitrogen, nitrogen substituted for boron, carbon substituted for nitrogen, carbon substituted for boron, boron vacancy, nitrogen vacancy, and combinations thereof. 
     
     
         5 . The method of  claim 1 , wherein the heterogeneous catalyst at least partially comprises a boron-rich solid such as boron produced through the chemical etching of metal borides. 
     
     
         6 . The method of  claim 1 , wherein the heterogeneous catalyst is substantially free of metals. 
     
     
         7 . The method of  claim 1 , wherein the hydrocarbon or carbon source is selected from a group comprising of methane, ethane, propene, allene, propyne, cyclohexene, other higher molecular weight hydrocarbons, CO 2 , CO, or air. 
     
     
         8 . The method of of  claim 1 , wherein the chamber is pressurized up to 276 kPA. 
     
     
         9 . The method of  claim 1 , wherein the light source comprises an excitation laser, a UV LED, a high intensity discharge lamp, or a solar source. 
     
     
         10 . The method of  claim 9 , wherein the light source is an excitation laser. 
     
     
         11 . The method of  claim 10 , wherein the excitation laser has a wavelength from 380 nm to 750 nm. 
     
     
         12 . The method of  claim 11 , wherein the wavelength is 532 nm. 
     
     
         13 . The method of any of  claim 12 , wherein the excitation laser has a power from 4 mW to 500 mW. 
     
     
         14 . The method of  claim 13 , wherein the excitation laser has a power of 25 mW. 
     
     
         15 . The method of  claim 1 , wherein the excitation laser has an objective of 4x to 50x. 
     
     
         16 . The method of  claim 1 , wherein the heterogeneous catalyst is exposed to the excitation laser for a period consisting of seconds to hours. 
     
     
         17 . The method of  claim 1 , wherein the chamber has a temperature of 24° C. to 80° C. 
     
     
         18 . The method of  claim 17 , wherein the chamber has a temperature of 24° C. 
     
     
         19 . The method of  claim 1 , wherein the carbon structures are primarily composed of graphitic carbon. 
     
     
         20 . The method of  claim 1 , wherein the heterogeneous catalyst at least partially comprises boron-rich solids consisting of low dimensionality non-equilibrium carbon. 
     
     
         21 . The method of  claim 20 , wherein the boron has at least one catalytically active defect on a surface thereof.