Life cycle net energy assessment of sustainable H-2 production and hydrogenation of chemicals in a coupled photoelectrochemical device

Green hydrogen has been identified as a critical enabler in the global transition to sustainable energy and decarbonized society, but it is still not economically competitive compared to fossil-fuel-based hydrogen. To overcome this limitation, we propose to couple photoelectrochemical (PEC) water splitting with the hydrogenation of chemicals. Here, we evaluate the potential of co-producing hydrogen and methyl succinic acid (MSA) by coupling the hydrogenation of itaconic acid (IA) inside a PEC water splitting device. A negative net energy balance is predicted to be achieved when the device generates only hydrogen, but energy breakeven can already be achieved when a small ratio (similar to 2%) of the generated hydrogen is used in situ for IA-to-MSA conversion. Moreover, the simulated coupled device produces MSA with much lower cumulative energy demand than conventional hydrogenation. Overall, the coupled hydrogenation concept offers an attractive approach to increase the viability of PEC water splitting while at the same time decarbonizing valuable chemical production. Integrating green hydrogen production with the generation of valuable chemicals has the potential to increase the competitiveness of the system. Here, the authors quantitatively evaluate the energetic benefit of coupling hydrogen production with the hydrogenation of feedstocks in a photoelectrochemical device.

Automated summary

Researchers propose coupling photoelectrochemical water splitting with the hydrogenation of chemicals to co-produce hydrogen and methyl succinic acid. They found that using 2% of the generated hydrogen for the conversion of itaconic acid to methyl succinic acid can achieve energy breakeven. This coupled reaction not only increases the viability of photoelectrochemical water splitting but also reduces the carbon emissions from chemical production.