Hydrogen energy has been widely used as a renewable energy source to realize zero CO₂ emissions. Among the hydrogen production method, water electrolysis is attracting attention as an eco-friendly production method that complements the intermittent properties of renewable energy. There are two main water electrolysis technologies include anion exchange membrane water electrolysis (AEMWE) and proton exchange membrane water electrolysis (PEMWE). Between them, PEMWE has advantages such as high current density, low gas permeability, high gas purity, and high stability compared to AEMWE. Despite these advantages, there is a drawback in those noble-metal-based commercial catalysts used in PEMWE are expensive and rare. Therefore, there is a need for research on a transition metal-based catalyst that is abundant, cost-effective, and durable. To replace noble-metal Pt used as the cathode, various efforts have been made to control the hydrogen binding energy of transition metals similar to that of Pt. As one of the strategies for modifying the electronic structure, many efforts are being conducted to synthesize non-metal transition metal compounds such as chalcogenides, carbides, nitrides, phosphide, and borides.

In the present study, we demonstrated the nickel-based ternary catalysts that have a synergy effect of different electron transfer phenomena of transition metal phosphide (TMP) and transition metal boride (TMB). The TMPB ternary catalyst fabricated through electrodeposition could adjust the B/P ratio by controlling deposition potential/time at room temperature and ambient pressure. Catalytic activity for HER was tested by half-cell based on geometric current, specific activity connected with the results from the analysis on material properties. And then, single-cell was tested by using an optimized TMPB catalyst in the cathode. Previous, there were reports about ternary catalysts improved HER performance by modifying electron structure, but the single-cell operation has not been confirmed for practical application.