Researchers from the Pacific Northwest National Laboratory (PNNL), alongside collaborators from Oregon State University (OSU), have tested a catalyst which converts wastewater and seawater into hydrogen.
The molybdenum-phosphide (MoP) catalyst was tested with wastewater in a small reactor called a microbial electrolysis cell (MEC). In comparison to related studies, the MoP catalyst produced hydrogen fast times faster than other non-platinum catalysts.
“If you can produce hydrogen from seawater, the resource pool is pretty much unlimited,” said Yugan Shao, Material Scientist at PNNL and catalyst research leader.
Expanding on the MoP catalyst research, PNNL researchers then investigated the catalyst for use in MECs. The team began with the MoP combination due to its affinity for activating, or separating, water molecules.
The catalyst is tuneable meaning the amount of each mineral can be adjusted. According to the team’s hypothesis, the tuning would optimise the amount of hydrogen produced in a single reaction.
Under the microscope, the researchers discovered that the catalyst assembled into a mixture of two distinct crystal phases – MoP and MoP2.
The atomic structure for each phase differentiated which led to different reactions. Whilst MoP2 released hydrogen atoms from the water molecules, MoP converted the hydrogen atoms into hydrogen gas molecules. The two active sites boosted the overall reaction.
“We did not expect simultaneous formation of the two crystal phases. The two phases work way better than the single phase,” said Shao.
The PNNL and OSU will soon collaborate with researchers from Texas A&M University on a new project which builds on their research for hydrogen production with MEC.