Self-powered H2 production with bifunctional hydrazine as sole consumable

Abstract

Splitting hydrazine into H2 and N2 by electro-catalyzing hydrogen evolution and hydrazine oxidation reactions is promising for replacing fossil energy with H2. However, current hydrazine splitting is achieved using external powers to drive the two reactions, which is inapplicable to outdoor use. Here, Fe-doped CoS2 nanosheets are developed as a bifunctional electrocatalyst for the two reactions, by which direct hydrazine fuel cells and overall-hydrazine-splitting units are realized and integrated to form a self-powered H2 production system. Without external powers, this system employs hydrazine bifunctionally as the fuel of direct hydrazine fuel cell and the splitting target, namely a sole consumable, and exhibits an H2 evolution rate of 9.95 mmol h−1, a 98% Faradaic efficiency and a 20-h stability, all comparable to the best reported for self-powered water splitting. These performances are due to that Fe doping decreases the free-energy changes of H adsorption and adsorbed NH2NH2 dehydrogenation on CoS2.

Manipulating dehydrogenation kinetics through dual-doping Co3N electrode enables highly efficient hydrazine oxidation assisting self-powered H2 production

“…23) and can reach a maximum power density of 46.3 mW cm −2 at a cell voltage of 0.429 V (Fig. 7b), which is comparable with the recently reported values under similar working conditions 15,45,46 , which is also summarized in Supplementary Table 5. As a proof-of-concept, the self-powered H 2 production system is demonstrated by powering the OHzS electrolyzer using the DHzFC with typical images shown in Fig.…”

“…Excitingly, the PW-Co 3 N NWA/NF also exhibits Pt-like activity for HER with a low overpotential of 41 mV at 10 mA cm −2 and a small Tafel slope of 40 mV dec −1 , as well as excellent durability in 1.0 M KOH electrolyte. The potential of PW-Co 3 N NWA/NF for H 2 production is further evaluated as both anode and cathode catalyst for overall hydrazine splitting (OHzS), where an ultrasmall operation voltage of 28 mV is needed to achieve current density of 10 mA cm −2 , and only 277 mV is required to reach 200 mA cm −2 , indicating the remarkable results compared with previous literatures 15,16 . Density functional theory (DFT) calculations indicate that the P/W doping can not only largely decrease the free-energy changes of the dehydrogenation of adsorbed NH 2 NH 2 (denoted as *NH 2 NH 2 ), but also make the free energy of adsorbed H (ΔG H* ) more thermoneutral compared to pristine Co 3 N. Furthermore, the proof-of-concept self-powered H 2 production system is demonstrated by integrating a direct hydrazine fuel cell (DHzFC) with an OHzS device using PW-Co 3 N NWA/NF as the bifunctional catalyst and hydrazine as the sole liquid fuel, with a decent H 2 evolution rate of 1.25 mmol h −1 at room temperature.…”

“…Recently, it has been demonstrated to possibly overcome this obstacle by replacing anodic OER with thermodynamically more favorable electrocatalytic oxidation of small molecules, including tetrahydroisoquinoline 9 , benzyl alcohol 10 , urea [11][12][13][14] and hydrazine [15][16][17] , which can hugely decease the cell voltage for H 2 production. Among these, hydrazine oxidation reaction (HzOR, N 2 H 4 + 4OH − →N 2 + 4H 2 O + 4e − ) possesses unique feature of tremendously lower theoretical potential of −0.33 V (vs. RHE) compared to that of OER (1.23 V vs. RHE) 18 .…”

Recent Advances in Electrochemical Hydrogen Production from Water Assisted by Alternative Oxidation Reactions

“…In another recent breakthrough achieved by Ding and co‐workers, Fe‐doped CoS 2 nanosheets were developed as a bifunctional electrocatalyst for both the HER and HzOR . As depicted in Figure a–c, the Fe‐doped CoS 2 nanosheets featured an ultrathin thickness of 1.22±0.03 nm.…”

Creating Competitive Active Sites on CNTs Walls by N‐Doping and Sublayer Co4N Encapsulating for Efficient Hydrogen Evolution Reaction

“…It is imperative to develop a low‐cost hydrogen evolution reaction (HER) catalyst . Transition metals alloys and transition metals compounds, such as metal alloys, metal phosphide, metal nitride, metal carbide, and metal sulfide/fluoride with defect have shown their outstanding HER catalysis activity. Carbon materials such as heteroatom‐doped graphene, C 3 N 4 @N doped graphene and metal‐free covalent organic polymer (COPs) also showed excellent catalytic ability for hydrogen evolution reaction with easily prepared process.…”