Acid‐durable, high‐performance cobalt phosphide catalysts for hydrogen evolution in proton exchange membrane water electrolysis. (8th June 2021)

• Record Type: Journal Article
• Authors: Yoon, Young; Kim, Hoyoung; Kim, Soo‐Kil; Kim, Jae Jeong
• Is Part Of: International journal of energy research. Volume 45:Number 11(2021)
• Page Start: 16842
• Page End: 16855
• Publication Date: 2021-06-08
• Subjects: cobalt phosphide -- hydrogen economy -- hydrogen evolution reaction -- non‐platinum group‐metal catalyst -- proton exchange membrane water electrolyzers; Power resources -- Periodicals; Power (Mechanics) -- Periodicals; Power resources -- Research -- Periodicals; 621.042
• DOI: 10.1002/er.6936
• Languages: English
• ISSNs: 0363-907X

Abstract

Summary: The cost of platinum group metal (PGM) catalysts is one of the major obstacles in commercializing proton exchange membrane water electrolyzers (PEMWEs). The non‐PGM substituents are often more financially beneficial but low in activity and durability in the acidic environment. In this study, cobalt phosphide catalysts, which are promising non‐PGM alternatives for the hydrogen evolution reaction (HER) and have enhanced durability and single‐cell performance, were fabricated directly on carbon paper using the pulse electrodeposition method. As the dissolution potential (reported as ‐ x vs saturated calomel electrode) of the pulse electrodeposition shifted in the positive direction, the P/Co ratio of the Co‐P‐ x catalysts increased because of severe Co dissolution. Among the catalysts, Co‐P‐0.6, Co‐P‐0.5, and Co‐P‐0.4 (where the number indicates the negative dissolution potential) were rapidly degraded in acid, whereas Co‐P‐0.3, Co‐P‐0.2, and Co‐P‐0.1 showed high stability because of the relative amounts of CoP and Co2 P phases. The acid‐dissolved Co‐P‐0.3 catalyst showed the best half‐cell performance (an overpotential of 143.85 mV at 10 mA/cm 2 ) and durability, and the P‐Co and Co δ+ surface states are critical for its performance. Single‐cell tests using the Co‐P‐0.3 cathode revealed its remarkable performance of 1.89 A/cm 2 at 2.0 Vcell, indicating its promise as a non‐PGM cathode material for PEMWEs. Abstract : To overcome the intrinsic problems of low activity and durability of nonprecious hydrogen evolution reaction (HER) catalysts in proton exchange membrane water electrolyzers (PEMWEs), cobalt phosphide (Co‐P) catalysts with various compositions are pulse‐electrodeposited directly on porous transport layer of carbon paper. It is confirmed that the relative amount of CoP/Co2 P phases, as well as the surface states of P‐Co and Co δ+, are critical for the performance. As a result, the acid‐treated Co94 P6 (Co‐P‐0.3) shows the best performance (143.85 mV at 10 mA/cm 2 ) and cycling durability for the hydrogen evolution reaction in a half‐cell level. When used as a cathode catalyst in PEMWE single‐cell, Co‐P‐0.3 enables superior performance of 1.89 A/cm 2 at 2.0 Vcell indicating its promise as a nonprecious cathode material for PEMWEs.