Self-Co-Electrolysis for Co-Production of Phosphate and Hydrogen in Neutral Phosphate Buffer Electrolyte

The spontaneous reaction between Zn and H₂ O is of critical importance and could plausibly be used to produce H₂ gas, especially under neutral conditions. However, this reaction has long been overlooked owing to its sluggish kinetics and Zn consumption. Herein, a unique self-co-electrolysis system (SCES) is reported, which uses a Zn anode, a CoP-based catalytic cathode, and a neutral phosphate buffer solution (PBS) as the electrolyte. In this SCES, Zn is not only a sacrificial anode but also an important precursor of high-value-added NaZnPO₄ . Additionally, the composition and phase structure of NaZnPO₄ can be well regulated. In this study, a high-performance N,Cu-CoP/carbon cloth (CC) catalyst is synthesized to catalyze the cathodic hydrogen evolution reaction (HER) at an especially low overpotential of 64.7 mV at 10 mA cm^{- 2} . H₂ gas (13.7 mL cm^{- 2} h^{- 1} ) and NaZnPO₄ (3.73 mg cm^{- 2} h^{- 1} ) are obtained at the cathode and anode, respectively, in the N,Cu-CoP/CC||Zn SCES spontaneously. Moreover, the SCES has a favorable open-circuit voltage (OCV) of 0.79 V and a maximum power density of 1.83 mW cm^{- 2} . Density functional theory (DFT) calculations are performed to elucidate the electronic structure and HER catalytic mechanism of the N and Cu co-doped CoP catalysts.