This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Generating hydrogen without releasing carbon dioxide sounds simple: pass electricity through water, split water molecules and generate green hydrogen. The hard part is the electrocatalyst.
The best ones rely on platinum, ruthenium and iridium, which are scarce and expensive. We wanted to know whether a small amount of iron and nickel oxides, anchored on carbon nanofibers grown by chemical vapor deposition the right way on the right scaffold, could do the job instead. Our results are published in ACS Applied Nano Materials.
Most hydrogen today comes from fossil fuels. Coal gasification and steam reforming of natural gas supply about 96% of the market. Producing 1 kilogram (2.2 pounds) of gray hydrogen releases about 10 kilograms (22 pounds) of carbon dioxide, and blue hydrogen releases about 6 kg (13 pounds).
Green hydrogen, made by splitting water, avoids these emissions. Water splitting has two half-reactions: the oxygen evolution reaction at the anode and the hydrogen evolution reaction at the cathode. Both need an electrocatalyst to run at practical voltages.
Our scaffold is Ti₃C₂Tₓ MXene, a two-dimensional material that conducts electricity efficiently. MXene sheets tend to oxidize and restack, which raises resistance. We tackled this by growing carbon nanofibers directly on the sheets.
We mixed the MXene with an iron or nickel precursor, dried it and heated it under nitrogen to 400°C (752°F). We then raised the temperature to 720°C (1,328°F) and fed acetylene as a carbon source for two hours, performing chemical vapor deposition to grow carbon nanofibers. The metal oxide particles sit at the tip of each growing fiber, a process called tip growth.
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