The modulation of the electronic structure is the effective
access
to achieve highly active electrocatalysts for the hydrogen evolution
reaction (HER). Transition-metal phosphide-based heterostructures
are very promising in enhancing HER performance but the facile fabrication
and an in-depth study of the catalytic mechanisms still remain a challenge.
In this work, the catalytically inactive n-type CeO
x
is successfully combined with p-type CoP to form the CoP/CeO
x
heterojunction. The crystalline–amorphous
CoP/CeO
x
heterojunction is fabricated
by the phosphorization of predesigned Co(OH)2/CeO
x
via the as-developed reduction–hydrolysis
strategy. The p–n CoP/CeO
x
heterojunction
with a strong built-in potential of 1.38 V enables the regulation
of the electronic structure of active CoP within the space–charge
region to enhance its intrinsic activity and facilitate the electron
transfer. The functional CeO
x
entity and
the negatively charged CoP can promote the water dissociation and
optimize H adsorption, synergistically boosting the electrocatalytic
HER output. As expected, the heterostructured CoP/CeO
x
-20:1 with the optimal ratio of Co/Ce shows significantly
improved HER activity and favorable kinetics (overpotential of 118
mV at a current density of 10 mA cm–2 and Tafel
slope of 77.26 mV dec–1). The present study may
provide new insight into the integration of crystalline and amorphous
entities into the p–n heterojunction as a highly efficient
electrocatalyst for energy storage and conversion.
An amorphous NiCoFeCrMo-based high-entropy hydroxide possesses the maximum content of high-valence Ni3+ species, boosting the oxygen evolution electrocatalytic performance.
Accomplishing a green hydrogen economy in reality through water spitting ultimately relies upon earth-abundant efficient electrocatalysts that can simultaneously accelerate the oxygen and hydrogen evolution reactions (OER and HER). The perspective of electronic structure modulation via interface engineering is of great significance to optimize electrocatalytic output but remains a tremendous challenge. Herein, an efficient tactic has been explored to prepare nanosheet-assembly tumbleweed-like CoFeCe-containing precursors with time-/energy-saving and easy-operating features. Subsequently, the final metal phosphide materials containing multiple interfaces, denoted CoP/FeP/CeO x , have been synthesized via the phosphorization process. Through the optimization of the Co/Fe ratio and the content of the rare-earth Ce element, the electrocatalytic activity has been regulated. As a result, bifunctional Co3Fe/Ce0.025 reaches the top of the volcano for both OER and HER simultaneously, with the smallest overpotentials of 285 mV (OER) and 178 mV (HER) at 10 mA cm −2 current density in an alkaline environment. Multicomponent heterostructure interface engineering would lead to more exposed active sites, feasible charge transport, and strong interfacial electronic interaction. More importantly, the appropriate Co/Fe ratio and Ce content can synergistically tailor the d-band center with a downshift to enhance the per-site intrinsic activity. This work would provide valuable insights to regulate the electronic structure of superior electrocatalysts toward water splitting by constructing rare-earth compounds containing multiple heterointerfaces.
The oxygen evolution reaction (OER) is kinetically sluggish due to the limitation of the four-electron transfer pathway, so it is imperative to explore advanced catalysts with a superior structure and catalytic output under facile synthetic conditions. In the present work, an easily accessible strategy was proposed to implement the plant-polyphenol-involved coordination assembly on Co(OH)2 nanosheets. A TA-Fe (TA = tannic acid) coordination assembly growing on Co(OH)2 resulted in the heterostructure of Co(OH)2@TA-Fe as an electrocatalyst for OER. It could significantly decrease the overpotential to 297 mV at a current density of 10 mA cm−2. The heterostructure Co(OH)2@TA-Fe also possessed favorable reaction kinetics with a low Tafel slope of 64.8 mV dec−1 and facilitated a charge-transfer ability. The enhanced electrocatalytic performance was further unraveled to be related to the confined growth of the coordination assembly on Co(OH)2 to expose more active sites, the modulated surface properties and their synergistic effect. This study demonstrated a simple and feasible strategy to utilize inexpensive biomass-derived substances as novel modifiers to enhance the performance of energy-conversion electrocatalysis.
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