Abstract
The study of hydrogen evolution reaction and oxygen evolution reaction electrocatalysts for water electrolysis is a developing field in which noble metal-based materials are commonly used. However, the associated high cost and low abundance of noble metals limit their practical application. Non-noble metal catalysts, aside from being inexpensive, highly abundant and environmental friendly, can possess high electrical conductivity, good structural tunability and comparable electrocatalytic performances to state-of-the-art noble metals, particularly in alkaline media, making them desirable candidates to reduce or replace noble metals as promising electrocatalysts for water electrolysis. This article will review and provide an overview of the fundamental knowledge related to water electrolysis with a focus on the development and progress of non-noble metal-based electrocatalysts in alkaline, polymer exchange membrane and solid oxide electrolysis. A critical analysis of the various catalysts currently available is also provided with discussions on current challenges and future perspectives. In addition, to facilitate future research and development, several possible research directions to overcome these challenges are provided in this article.Graphical
Highlights
Energy is a necessity for the economic and social development of the world, and currently, ~ 65% of the global energy demand is fulfilled by non-renewable fossil fuels [1,2,3]
Based on the discussions above for solid oxide electrolysis cell (SOEC) oxygen electrodes, electrode materials can be classified into three main categories: (1) noble metals such as Pt or Ag that can be used as oxygen electrode in SOECs but are very expensive and difficult to apply commercially; (2) ceramic electrodes such as SFM, Linear sweep voltammetry (LSV), LSCM and LSM that possess good ionic and electrical conductivities but are catalytically slow and unstable; and (3) composite electrodes such as Ni–YSZ, NI–SDC, LSC–YSZ and LSM–YSZ that possess enhanced catalytic activities and thermal expansions matching with electrolytes [221,222,223,224,225,226,227,228,229,230]
The SOEC is the reverse of the solid oxide fuel cell (SOFC); the anode/ cathode of SOFCs can be used as the cathode/anode for
Summary
Energy is a necessity for the economic and social development of the world, and currently, ~ 65% of the global energy demand is fulfilled by non-renewable fossil fuels [1,2,3].
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