Electrochemical Flocculation Integrated Hydrogen Evolution Reaction of Fe@N‐Doped Carbon Nanotubes on Iron Foam for Ultralow Voltage Electrolysis in Neutral Media

Abstract

Hydrogen (H2) production is a key step in solving the energy crisis in the future. Electrocatalytic water splitting suffers from sluggish anodic oxygen evolution reaction (OER) kinetics leading to low energy conversion efficiency. Herein, a strategy is presented that integrates anodic electrochemical flocculation with cathodic hydrogen production from water splitting in 0.5 m Na2SO4. Iron encapsulated in a nitrogen‐doped carbon nanotubes array on iron foam (Fe@N‐CNT/IF) is employed as an electrode for the hydrogen evolution reaction (HER), and the Fe@N‐CNT/IF possesses superior HER activity requiring an overpotential of 525 mV to achieve 10 mA cm−2, which is close to that of 20 wt% Pt/C. Benefiting from the lower oxidation potential of iron (E°Fe/Fe2+, 0.44 V) than that of OER (E0OH‐/O2, 1.23 V), the cell voltage for integrated electrochemical flocculation and H2 production is significantly reduced by 1.31 V relative to overall water splitting to achieve 20 mA cm−2. More important, the production of electrochemical flocculation can be applied to water purification, because of the excellent adsorption capacity. Finally, metal–carbon electrocatalysts are prepared again by pyrolysis of flocculation adsorbents containing toxic heavy metals and organics. This result provides a new direction for designing a heterogeneous electrolysis system for energy conversion and environmental treatment applications.

Recent Achievements in Polymer Bio-Based Flocculants for Water Treatment

“…Advanced nanomaterials are proposed for electrochemical flocculation (electrocoagulation) which is applied not only for water purification but also for water splitting for hydrogen production [ 228 , 229 ]. This electrochemical purification process consists in the destabilizing suspended, emulsified, or dissolved contaminants in an aqueous medium by an electric current.…”

“…This electrochemical purification process consists in the destabilizing suspended, emulsified, or dissolved contaminants in an aqueous medium by an electric current. An example of such material designed for electrode is iron encapsulated in nitrogen-doped carbon nanotubes, described in detail by Yu and coworkers [ 228 ].…”

Synthesis of N-rGO-MWCNT/CuCrO2 Catalyst for the Bifunctional Application of Hydrogen Evolution Reaction and Electrochemical Detection of Bisphenol-A

“…Increasing the energy crisis, environmental pollution, climate change, and energy shortages by excessive fossil fuel consumption, so the need to seek clean, cheap, safe and viable renewable energy resources has become very important [1]. Hydrogen (H 2 ) has received considerable attention recently as a next-generation energy carrier.…”

“…Furthermore, H 2 is a prospective fuel, it is produced as a by-product of the reaction of carbon dioxide with water. At present, the predominant method for H 2 production is the non-renewable steam reforming process, which increases fossil fuel usage and carbon dioxide emission [1,5]. Among the other H 2 production methods, water splitting technology is the most favorable, environmental-friendly, and efficient for H 2 generation [6,7].…”

Cu(OH)2 Nanorods/Ni(OH)2 Nanosheets as Highly Efficient Catalyst for Hydrogen Evolution Reaction

“…In the process of H 2 evolution, catalysts play an important role in increasing H 2 production efficiency and reducing energy consumption. [10,11] Bearing this fact in mind, much efforts have been made to develop high efficient catalysts. So far, some precious metal catalysts, for instance RuO 2 , Pt/C, and Ir/C, offer a satisfactory catalytic performance for hydrogen evolution reaction (HER).…”