Regulating Ni site in NiV LDH for efficient electrocatalytic production of formate and hydrogen by glycerol electrolysis

Energy-saving glycerol electrolysis with lower potential than water spitting endows a promising way for the concurrent production of value-added formate and high-purity hydrogen. However, there is still lack of efficient electrocatalysts at both anode and cathode for glycerol electrolysis. Herein, we report the activation of Ni site in NiV layered double hydroxide (LDH) by electrochemical and N2/H2 plasma regulations for boosting the activity of glycerol oxidation reaction (GOR) and hydrogen evolution reaction (HER), respectively. Specifically, boosted GOR performance with a low overpotential (1.23 V at 10 mA·cm−2) and a high Faradic efficiency (94%) is demonstrated by electrochemically regulated NiV LDH (E-NiV LDH) with elevated valence state of Ni site. In situ Raman spectrum reveals the generation of Ni(III) species by electrochemical regulation, and the highly active Ni(III) can be regenerated with the process of electrochemical oxidation. Additionally, the possible reaction pathway is speculated based on the in situ Fourier transform infrared spectroscopy (FTIR) and high-performance liquid chromatography results. The plasma-regulated NiV LDH (P-NiV LDH) with lower valence state of Ni site exhibits outstanding HER activity, displaying a low overpotential of 45 mV to deliver 10 mA·cm−2. When employing E-NiV LDH and P-NiV LDH as anode and cathode electrocatalyst, respectively, the assembled electrolyzer merely needs 1.25 V to achieve 10 mA·cm−2 for simultaneous production of formate and hydrogen, demonstrating remarkable 320 mV of lower potential than water electrolysis.Graphic abstract