Seawater is one of the most abundant resources on Earth and promises both hydrogen ̵
University of Houston researchers have achieved a major breakthrough with a new oxygen evolution reaction catalyst that, in combination with a hydrogen evolution reaction catalyst, achieves current densities that meet industry requirements while requiring a relatively low voltage to start seawater electrolysis.  Researchers say that the device, which consists of cheap non-noble metal nitrides, avoids many of the barriers that previous attempts to produce cheap hydrogen or safe drinking water from seawater have limited. The work is described in Nature Communications .
Zhifeng Ren, director of the Texas Center for Superconductivity at UH and a corresponding author of the publication, said a major obstacle was the lack of a catalyst that effectively splits seawater to produce hydrogen without removing ions from it Sodium, chlorine, calcium and other components of seawater that can deposit on the catalyst and make it inactive. Chlorine ions are particularly problematic, in part because only a slightly higher voltage is required for the release of chlorine than for the release of hydrogen.
The researchers tested the seawater catalysts from Galveston Bay off the Texas coast. Ren, MD Anderson chairman, professor of physics at UH, said it would also work with wastewater and provide another source of hydrogen from water that would be unusable without costly treatment.
"Most people use clean fresh water to produce hydrogen by splitting water," he said. "However, the availability of clean fresh water is limited."
To address these challenges, researchers developed and synthesized a three-dimensional core-shell catalyst for oxygen evolution using transition metal nitride with nanoparticles from a nickel-iron atom. Nitride compound and nickel molybdenum nitride nanorods on porous nickel foam.
First author Luo Yu, a postdoctoral fellow at UH, who also works at Central China Normal University, said the new catalyst for the oxygen evolution reaction was paired with a previously described nickel-molybdenum-nitride nanorod hydrogen evolution reaction catalyst.
The catalysts were integrated into a two-electrode alkaline electrolyzer, which can be operated with waste heat via a thermoelectric device or with an AA battery.
Required cell voltages to produce a current density of 100 milliamps per square centimeter (a measure of the current density or mA cm-2) in the range of 1.564 V to 1.581 V.
The voltage According to Yu, this is important because while a voltage of at least 1.23 V is required to produce hydrogen, at a voltage of 1.73 V, chlorine is generated at two levels.
Researchers report novel hybrid catalysts for the splitting of water
Luo Yu et al. Non-noble metal nitride based electrocatalysts for alkaline seawater high performance electrolysis, Nature Communications (2019). DOI: 10.1038 / s41467-019-13092-7
New catalyst efficiently generates hydrogen from seawater (2019, 11 November)
retrieved on November 11, 2019
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