Energy-efficient electrolytic H₂ production and high-value added H₂-acid-base co-electrosynthesis modes enabled by a Ni₂P catalyst in a diaphragm cell

Reducing the energy consumption and increasing the additional value of water electrolysis to produce H₂ is currently a hot research topic. In this work, we introduce two kinds of promising water electrolysis modes in a diaphragm electrolytic cell for H₂ production. When considering the energy consumption, a urea-assisted amphoteric water splitting system was built. This system just needs an ultralow voltage of 0.88 V to attain the current density of 10 mA cm⁻² with high durability, which leads to a large decrease of energy consumption of 48.55% compared to alkaline water splitting system by the introduction of electrochemical neutralization energy and thermodynamically-favorable urea oxidation reaction. When considering the additional value, a H₂-acid-base co-electrosynthesis system was proposed inspired by the chlor-alkali and electrochemical seawater desalination processes. In this system, only K₂SO₄ electrolytes are needed, and acid-base chemicals and H₂ could be generated at a voltage of 2.32 V (10 mA cm⁻²).