Fig. 3: Matching verification of the chemical reduction reaction and electrochemical oxidation reaction.

A Schematic diagram of the in situ UV‒vis monitoring system. B In situ UV‒vis spectra obtained during AQDS hydrogenation. C Schematic showing the potential monitoring system for hydrogenation reduction. D OCV curve of the AQDS hydrogenation reduction process. The electrolyte was 100 mL of 0.1 M AQDS in phosphate buffer. The catalyst loading volume was 50 mL. The H₂ flow rate was 30 mL min⁻¹. The temperature was 50 °C. The electrolyte was injected with Ar during the tests. E The Q/QH₂ ratio during the hydrogenation process was calculated with the Nernst equation. The dots are reaction data, and the line reflects a linear fit to the data. F Schematic of the full-cell electrolysis system. G, H Constant voltage electrolysis test of the full cell under different pump flow rates. The initial electrolyte was fully oxidized to 0.1 M AQDS in phosphate buffer and 1 M KHCO₃. Hydrogen gas was introduced for hydrogenation reduction at 20 min.