15August2020

Nano-Micro Letters

Arrayed Cobalt Phosphide Electrocatalyst Achieves Low Energy Consumption and Persistent H2 Liberation from Anodic Chemical Conversion

Kai Zhang1, 4, Gong Zhang2, Qinghua Ji2, Jiuhui Qu2, 3, Huijuan Liu1, 2, *

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Nano-Micro Lett. (2020) 12: 154

First Online: 22 July 2020 (Article)

DOI:10.1007/s40820-020-00486-2

*Corresponding author. E-mail: hjliu@rcees.ac.cn or hjliu@tsinghua.edu.cn (Huijuan Liu)

 

Abstract

 


Toc

Electrochemical reduction of water to hydrogen (H2) offers a promising strategy for production of clean energy, but the design and optimization of electrochemical apparatus presents challenges in terms of H2 recovery and energy consumption. Using cobalt phosphide nanoarrays (Co2P/CoP NAs) as a charge mediator, we effectively separated the H2 and O2 evolution of alkaline water electrolysis in time, thereby achieving a membrane-free pathway for H2 purification. The hierarchical array structure and synergistic optimization of the electronic configuration of metallic Co2P and metalloid CoP make the Co2P/CoP NAs high-efficiency bifunctional electrocatalysts for both charge storage and hydrogen evolution. Theoretical investigations revealed that the introduction of Co2P into CoP leads to a moderate hydrogen adsorption free energy and low water dissociation barrier, which are beneficial for boosting HER activity. Meanwhile, Co2P/CoP NAs with high capacitance could maintain a cathodic H2 evolution time of 1500 s at 10 mA cm-2 driven by a low average voltage of 1.38 V. Alternatively, the energy stored in the mediator could be exhausted via coupling with the anodic oxidation of ammonia, whereby only 0.21 V was required to hold the current for 1188 s. This membrane-free architecture demonstrates the potential for developing hydrogen purification technology at low cost.

 

Keywords

Electrocatalysis, Cobalt phosphide, Hydrogen purification, Ammonia oxidation reaction, Membrane-free architecture

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