Fluorine-Induced Dual Defects in Cobalt Phosphide Nanosheets Enhance Hydrogen Evolution Reaction Activity

Abstract

Introduction of defects in a controllable way is important to modulate the electronic structure of catalysts towards enhancement of electrocatalytic activity. Herein, we report that fluorine incorporation into cobalt phosphide alloy has a unique effect -it creates both F-anion doping and P vacancy, which results in nearly 15-fold enhancement in catalytic activity for hydrogen evolution reaction (HER) in neutral solution. The existence of dual defects in CoP is confirmed by extended X-ray absorption fine structure (EXAFS) curve fitting results and density functional theory calculation. We show that the dual-defect feature is beneficial to increasing the Page 2 of 27 ACS Paragon Plus Environment ACS Materials Letters 3 active site exposure, tuning the surface wettability and optimizing the electronic configuration of CoP for HER. Our fluorine-based modulation protocol may be applicable to other metal alloy electrocatalysts towards more efficient energy conversion reactions. TOC GRAPHICSAmong the various new and sustainable energy systems, electrolysis of water is considered as a promising technology to generate hydrogen which is regarded as a potential alternative to fossil fuels. [1][2][3]

Dynamics and control of active sites in hierarchically nanostructured cobalt phosphide/chalcogenide-based electrocatalysts for water splitting

“…The rising absorption edge position of Co–P NBs is lower than that of Co(OH) 2 but higher than that of Co foil, suggesting that the average valence state of Co centers in Co–P NBs is slightly lower than +2. 12,23,59,66 To further explore the local electronic structure of the as-prepared catalysts, the XANES spectrum of Co–P NBs was calculated using ab initio finite difference methods using the model structure defined in the PDF card No. 29-0497 (S. G. Pnma ) as shown in Fig.…”

“…2a presents ex situ Co K-edge X-ray absorption near-edge structure (XANES) spectra of Co-P NBs, Co@CoFe-P NBs, Co@CoFe-O NBs, and the references Co foil, Co(OH) 2 , Co-FeOOH, Co 3 O 4 , and CoOOH. The rising absorption edge position of Co-PNBs is lower than that of Co(OH) 2 but higher than that of Co foil, suggesting that the average valence state of Co centers in Co-P NBs is slightly lower than +2 12,23,59,66. To further explore the local electronic structure of the as-prepared catalysts, the XANES spectrum of Co-P NBs was calculated using ab initio finite difference methods using the model structure defined in the PDF card No.…”

“…[15][16][17][18][19] Ex situ investigations suggest that the structural reconstruction associated with oxygen incorporation in TMCs and TMPs is responsible for their high OER performance. [20][21][22][23][24][25] This reconstruction can proceed via two different routes. Either the as-prepared bulk compounds are fully oxidized into transition metal oxides or (oxy)hydroxides, 19,[26][27][28][29] or their surfaces can reconstruct into core-shell structures with TMCs and TMPs remaining as core materials.…”

Nanostructured Metal Phosphide Based Catalysts for Electrochemical Water Splitting: A Review

“…This nanostructured material with dual effects of doping and creating P-vacancies exhibited the best catalytic performance with the requirement of a small overpotential 108 mV at 10 mA cm −2 . [118] Chen et al demonstrated the role of anion for enhancing the HER activity in NiP 1.92 Se 0.08 catalyst through Fourier-transformed-extended X-ray absorption fine structure (FT-EXAFS) studies. The catalyst exhibited HER overpotential of 81 mV to drive the current density of 10 mA cm −2 .…”

Superaerophobic/superhydrophilic surfaces as advanced electrocatalysts for the hydrogen evolution reaction: a comprehensive review

“…117 As a result of their excellent chemical stability and electrical conductivity, transition metal phosphides (TMPs) have gained further consideration in HER research than transition metal oxides or suldes. [118][119][120] As a result, they are referred to as "quasi-platinum (Pt) catalysts". 121,122 Many methods have been used to make TMPs, including hydrothermal reactions, solvothermal reactions, electrodeposition methods, gamma-ray irradiation methods, and chemical vapor deposition (CVD).…”