Integration of Green Hydrogen Production and Storage via Electrocatalysis

Abstract

Hydrogen economy, which proposes employing hydrogen to replace or supplement the current fossil-fuel-based energy economy system, is widely accepted as the future energy scheme for the sustainable and green development of human society. While the hydrogen economy has shown tremendous potential, the associated challenges with hydrogen production and storage remain significant barriers to wide applications. In light of this consideration, the integration of green hydrogen production and storage through electrocatalysis for direct production of chemical hydrogen storage media has emerged as a potential solution to these challenges. Specifically, through electrocatalysis, CO₂ and H₂O can be converted into methanol or formic acid, while N₂ or NO _x along with H₂O can be transformed into ammonia, streamlining the hydrogen economy scheme. In this Perspective, we provide an overview of recent developments in this technology. Additionally, we briefly discuss the general properties and corresponding production strategies via the electrolysis of these chemical hydrogen storage media. Finally, we conclude by offering insights into future perspectives in this field, anticipating that the successful advancement of such technology will propel the development of the hydrogen economy toward practical implementation.

Figure 1

Schematic illustration of (a) traditional hydrogen production and storage and (b) integration hydrogen production and storage routes.

Figure 2

General properties of methanol for hydrogen storage.

Figure 3

(a) Linear sweep voltammetry curves over different catalysts in a CO₂-saturated or N₂-saturated BMImBF₄/H₂O (molar ratio of 1:3) electrolyte with the scan rate of 10 mV s^–1. (b) Product selectivity and current density for optimized Ag,S comodified Cu₂O/Cu at different applied potential. Reprinted with permission from ref (28). Copyright 2022, Springer Nature. (c,d) Schematic illustration of the Cu catalytic sites of the common Cu catalysts (e.g., Cu and Cu₂O) (c) and Cu sites on Cu₂NCN (d). Typical Cu catalytic sites own a relatively strong Cu–O bond (bond dissociation enthalpy, ΔH_Cu–O > 450 kJ mol^–1) compared with the O–C bond (ΔH_O–C of OCH₃ < 380 kJ mol–1), causing the cleavage of the O–C bond to release *CH₃ and form CH₄. ΔH_Cu–O value can be tuned to be lower than ΔH_O–C value on Cu₂NCN to enhance formation of CH₃OH. Reprinted with permission from ref (29). Copyright 2023, Springer Nature.

Figure 4

General properties of formic acid for hydrogen storage.

Figure 5

(a) Linear sweep voltammetry curves of defective Bi in CO₂-saturated or N₂-saturated 0.5 M KHCO₃ electrolyte. (b) Product selectivity for defective Bi at different applied potential. Reprinted with permission from ref (37). Copyright 2019, Springer Nature.

Figure 6

(a) Formate Faradaic efficiency over different catalysts under various current density in flow cell. (b) Schematic illustration of the ECO₂RR in the MEA containing solid-state electrolytes to produce pure HCOOH solution. (c) Long-term stability test and the corresponding formate Faradaic efficiency at 200 mA cm^–2 in MEA containing solid-state electrolytes. Reprinted with permission from ref (40). Copyright 2024, John Wiley and Sons.

Figure 7

General properties of ammonia for hydrogen storage.

Figure 8

(a) Ammonia production rate (R_NH3) and ammonia FE of EN₂RR using optimized Fe and Co single-atoms anchored bacterial cellulose. (b) Chronoamperometric curves of Fe and Co single-atoms anchored bacterial cellulose obtained from three replicated stability tests at −0.30 V versus RHE. Reprinted with permission from ref (43). Copyright 2023, Springer Nature.

Figure 9

(a,b) NH₃ FE and current with the different voltage (a) and ammonia production rate as a function of current (b) of ENORR using Cu₆Sn₅ catalyst in a MEA electrolyzer. Reprinted with permission from ref (47). Copyright 2023, Springer Nature. (c,d) NH₃ yield rate (c) and NH₃ FE of ENO_xRR using Cu incorporated PTCDA at different applied voltage. Reprinted with permission from ref (48). Copyright 2020, Springer Nature.