Separating hydrogen and oxygen evolution in alkaline water electrolysis using nickel hydroxide

Abstract

Low-cost alkaline water electrolysis has been considered a sustainable approach to producing hydrogen using renewable energy inputs, but preventing hydrogen/oxygen mixing and efficiently using the instable renewable energy are challenging. Here, using nickel hydroxide as a redox mediator, we decouple the hydrogen and oxygen production in alkaline water electrolysis, which overcomes the gas-mixing issue and may increase the use of renewable energy. In this architecture, the hydrogen production occurs at the cathode by water reduction, and the anodic Ni(OH)2 is simultaneously oxidized into NiOOH. The subsequent oxygen production involves a cathodic NiOOH reduction (NiOOH→Ni(OH)2) and an anodic OH− oxidization. Alternatively, the NiOOH formed during hydrogen production can be coupled with a zinc anode to form a NiOOH-Zn battery, and its discharge product (that is, Ni(OH)2) can be used to produce hydrogen again. This architecture brings a potential solution to facilitate renewables-to-hydrogen conversion.

Tuning of CO2 Reduction Selectivity on Metal Electrocatalysts

“…Although water is one of the most abundant materials for anodes, gaseous O 2 generated at anode is earth‐abundant and requires a large amount of energy consumption because of the sluggish kinetics of water oxidation . In light of previous research on water splitting systems without the assistance of ion‐exchange membranes and with lower cost of electricity, the design of devices for CO 2 electroreduction with low cost and energy consumption may be realized and rewarding in the near future. (iii)Electroreduction of CO 2 in air. Although natural green plants only possess a low solar‐to‐fuel efficiency, they realize CO 2 fixation in air with only ≈400 ppm gaseous CO 2 , whereas almost all artificial photosynthesis or electrochemical CO 2 reduction devices have to be operated in 100% CO 2 condition, especially those systems based on inorganic electrocatalysts .…”

An Insight on the Electrocatalytic Mechanistic Study of Pristine Ni MOF (BTC) in Alkaline Medium for Enhanced OER and UOR

“…[1,2] Water electrolysis (WE) has been considered as a promising way to produce high pure H 2 than compared to earlier hydrocarbon and steam reformation process. [2,[4][5][6][7][8][9][10][11] In water electrolysis, anodic 4e À transfer oxygen evolution reaction (OER) is the limiting factor than compared to cathodic 2e À transfer hydrogen evolution reaction (HER). [2,[4][5][6][7][8][9][10][11] In water electrolysis, anodic 4e À transfer oxygen evolution reaction (OER) is the limiting factor than compared to cathodic 2e À transfer hydrogen evolution reaction (HER).…”

Hierarchical Hollow Nanoprisms Based on Ultrathin Ni‐Fe Layered Double Hydroxide Nanosheets with Enhanced Electrocatalytic Activity towards Oxygen Evolution

“…[7,8] Many research efforts have been devoted to developing cost-effective electrocatalysts to replace the state-of-the-art precious-metal-based catalysts. [9][10][11][12][13][14][15][16][17][18][19] Among various promising alternatives,oxides/hydroxides containing first-row transition metals (e.g., Mn, Fe,C o, and Ni)h ave attracted tremendous interest owing to their earth abundance and remarkable OER performance. [12][13][14][15][16][17][18][19] In particular,N i-Fel ayered double hydroxides (LDHs) have been reported as apromising class of most effective OER catalysts in alkaline environments (pH [13][14].…”

“…[9][10][11][12][13][14][15][16][17][18][19] Among various promising alternatives,oxides/hydroxides containing first-row transition metals (e.g., Mn, Fe,C o, and Ni)h ave attracted tremendous interest owing to their earth abundance and remarkable OER performance. [12][13][14][15][16][17][18][19] In particular,N i-Fel ayered double hydroxides (LDHs) have been reported as apromising class of most effective OER catalysts in alkaline environments (pH [13][14]. [20][21][22][23][24][25][26][27] Although thorough investigations are still needed to identify the active sites,t he synergistic interactions between Ni and Fe can indeed dramatically enhance the catalytic activity compared with the individual Ni and Fe components.…”