Acid‐durable, high‐performance cobalt phosphide catalysts for hydrogen evolution in proton exchange membrane water electrolysis

Abstract

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 Co 2 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 V cell , indicating its promise as a non-PGM cathode material for PEMWEs.

Ternary Ni‐Mo‐P catalysts for enhanced activity and durability in proton exchange membrane water electrolysis

“…The difference in their electronegativities contributes to the peak shift and electron transfer. In our previous work, 57 the P‐metal state was reported to be more important than the P‐O state for both the HER activity and stability of metal phosphide catalysts. The activities of NiP and NiMoP can be explained by the competing effects between the electron‐withdrawing by P from the metal and the relative amounts of the P‐metal state.…”

A brief introduction of electrode fabrication for proton exchange membrane water electrolyzers

“…On top of that, electrodeposition is also capable to control the size and distribution of the catalyst on the conductive support by adjusting the operating parameters. Yoon et al reported an acid-durable cobalt phosphide (Co-P) catalyst synthesized via pulse electrodeposition on CP, where the P content was controlled by adjusting the applied dissolution potential [128]. The acid durability of the best-performing Co-P catalyst (Co-P-0.3, synthesized using dissolution potential of −0.3 V SCE ) was evaluated in 0.5 M H 2 SO 4 through an accelerated degradation test (ADT) comprising 500 cyclic voltammetry (CV) cycles.…”

Recent advances in solution assisted synthesis of transition metal chalcogenides for photo-electrocatalytic hydrogen evolution

“…266,267 Cobalt phosphide (Co x P) is a cost-effective and efficient cocatalyst alternative to noble metals. [268][269][270][271] For example, Wang et al reported a CoP-modified CdS heterostructure catalyst. Compared to pure CdS, the CdS/CoP composite shows improved hydrogen evolution activity.…”