Recent Advances in Hydrogen Production from Hybrid Water Electrolysis through Alternative Oxidation Reactions

Abstract

Water splitting driven by green electricity from renewable energy input to produce H2 has been widely considered as a promising strategy to realize the goals for future clean energy. However, in conventional overall water electrolysis, the sluggish kinetics and high onset potential of anode OER limit the cathode HER rate, which lowers the overall energy conversion efficiency. Over the past decade, an innovative concept involving hybrid water electrolysis by replacing OER with thermodynamically more favorable oxidation reactions coupling with the cathodic hydrogen evolution reaction has been devised to alleviate the limitations associated with the anodic OER. In this review, we summarize the recent progress concerning electrochemical hydrogen production by coupling the oxidation of molecules incorporating hydroxyl, aldehyde, and amino functional groups, with special emphasis on alternative reactions involving CO and sulfide. Finally, the remaining challenges and future perspectives are also discussed. We hope this review will accelerate the development of novel strategies for practicable H2 production from hybrid water electrolysis.

Metal–organic frameworks (MOFs) for hybrid water electrolysis: structure–property–performance correlation

“…Nevertheless, the process involves a four-electron transfer mechanism transitioning hydrazine to N 2 through consecutive dehydrogenation stages. 46,47 Hence, expediting both the dehydrogenation and N 2 desorption steps holds significant importance. Therefore, a series of MOFs have been employed to accelerate the dehydrogenation step of HzOR offering excellent performance.…”

“…Integrating AORs with the HER in a hybrid electrolyzer shows promise for reducing the overall voltage needed to produce H 2 efficiently. 45,46 This approach enables the simultaneous production of value-added compounds at the anode, which find applications in chemical, polymer, and pharmaceutical industries. 45,46 Despite progress, catalytic activity and cell designs still need advancement to meet real-world demands.…”

“…45,46 This approach enables the simultaneous production of value-added compounds at the anode, which find applications in chemical, polymer, and pharmaceutical industries. 45,46 Despite progress, catalytic activity and cell designs still need advancement to meet real-world demands. 38 Numerous transition-metal-derived electrocatalysts, including hydroxides, layered double hydroxides, phosphides, oxides, chalcogenides, borides, carbides, nitrides, and alloys, have been investigated in the literature for various oxidation reactions.…”

“…38 Numerous transition-metal-derived electrocatalysts, including hydroxides, layered double hydroxides, phosphides, oxides, chalcogenides, borides, carbides, nitrides, and alloys, have been investigated in the literature for various oxidation reactions. 44,46 These reactions encompass hydrazine oxidation reaction (HzOR), urea oxidation reaction (UOR), iodine oxidation reaction (IOR), glucose oxidation reaction (GOR), alcohol oxidation reaction (AlOR), amine oxidation reaction (AmOR), and biomass oxidation reaction (BOR). 45–48 Through these oxidation reactions, high-value added compounds are generated at the positive electrode concurrently with the production of hydrogen through cathodic reduction.…”

“…44,46 These reactions encompass hydrazine oxidation reaction (HzOR), urea oxidation reaction (UOR), iodine oxidation reaction (IOR), glucose oxidation reaction (GOR), alcohol oxidation reaction (AlOR), amine oxidation reaction (AmOR), and biomass oxidation reaction (BOR). 45–48 Through these oxidation reactions, high-value added compounds are generated at the positive electrode concurrently with the production of hydrogen through cathodic reduction. 47,48…”