High-entropy Phosphide Bifunctional Catalyst: Preparation and Performance of Efficient Water Splitting

doi:10.15541/jim20240074

Abstract

Abstract:

In the process of electrolyzing water to produce hydrogen, the sluggish electrocatalytic kinetics of the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) limit the energy conversion efficiency. High-entropy materials have been considered as potential catalysts due to their unique structural features and excellent performance, which could potentially replace traditional metal oxides and precious metals for energy conversion and water electrolysis. Due to the incompatibility between different metals and non-metals, there have been few reports on the synthesis of high-entropy compounds, especially high-entropy metal phosphides. In this study, a series of carbon-based high-entropy alloy phosphide nanoparticles were synthesized using citric acid as complexing agent and ammonium dihydrogen phosphate as phosphorus source via a low-temperature Sol-Gel method with different elemental metals. In 1 mol·L^-1 KOH solution, FeCoNiMoCeP/C exhibited good water electrolysis performance at a current density of 10 mA·cm^-2, with overpotentials of 119 and 240 mV for the HER and OER, respectively. Similarly, in overall water splitting studies, FeCoNiMoCeP/C also showed excellent catalytic activity. When operating at a current density of 10 mA·cm^-2, FeCoNiMoCeP/C required only 1.53 V as the combined anode and cathode voltage for electrolyzing water. This is due to the synergistic effects among the atoms of high-entropy phosphide catalysts which provide more reaction sites to increase reaction activity and selectivity. This study is expected to expand the potential applications of high-entropy alloys in the field of electrocatalysis.

Key words: high-entropy metal phosphide, bifunctional catalyst, overall water splitting, synergistic effect

CLC Number:

TQ116

ZHANG Wenyu, GUO Ruihua, YUE Quanxin, HUANG Yarong, ZHANG Guofang, GUAN Lili. High-entropy Phosphide Bifunctional Catalyst: Preparation and Performance of Efficient Water Splitting[J]. Journal of Inorganic Materials, 2024, 39(11): 1265-1274.

Figures/Tables 13

Fig. 1 (a) XRD patterns and (b-f) Raman spectra of different catalysts

Fig. 2 SEM images of FeCoNiMoCeP/C at different magnifications

Fig. 3 TEM and high-resolution TEM (HRTEM) images of FeCoNiMoCeP/C (a) TEM image; (b) HRTEM image and selected-area electron diffraction (SAED) image (inset) of the square region in (a); (c) HRTEM image of the circular region in (b); (d) Fast Fourier transform (FFT) and (e) inverse fast Fourier transform (IFFT) images of the square region in (c)

Fig. 4 High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images and corresponding EDS elemental mappings of different samples (a) FeP/C; (b) FeCoP/C; (c) FeCoNiP/C; (d) FeCoNiMoP/C; (e) FeCoNiMoCeP/C

Fig. 5 XPS spectra of FeCoNiMoCeP/C (a) Surve; (b) Fe2p; (c) Co2p; (d) Ni2p; (e) Mo3d; (f) Ce3d; (g) P2p

Fig. 6 OER and HER performance of different catalysts (a) OER LSV curves; (b) OER Tafel plots; (c) HER LSV curves; (d) HER Tafel plots. Colorful figures are available on website

Fig. 7 (a) Double-layer capacitance (Cdl) curves, (b) SECSA-normalized OER LSV curves, and (c) SECSA-normalized HER LSV curves for different catalysts; (d) Current-time (I-t) curve of FeCoNiMoCeP/C catalyst Inset in (d): LSV curves of FeCoNiMoCeP/C before and after 72 h stability test at 1.5 V. Colorful figures are available on website

Fig. 8 Performance analysis of FeCoNiMoCeP/C || FeCoNiMoCeP/C for overall water splitting (a) LSV curves of FeCoNiMoCeP/C || FeCoNiMoCeP/C and Pt/C || RuO2 with inset showing photograph of overall water splitting equipment with two electrodes; (b) I-t curve of FeCoNiMoCeP/C || FeCoNiMoCeP/C

Fig. S1 Atomic percentages of metal elements Fe, Co, Ni, Mo, and Ce in FeCoNiMoCeP/C catalyst measured by ICP-OES

Fig. S2 XPS spectra of different catalysts (a) Fe2p; (b) Co2p; (c) Ni2p; (d) Mo2p

Fig. S3 CV curves at different scan rates (a) FeCoNiMoCeP/C; (b) FeCoNiMoP/C; (c) FeCoNiP/C; (d) FeCoP/C; (e) FeP/C

Fig. S4 Structure morphology and EDS elemental mappings of FeCoNiMoCeP/C after stability test for 72 h (a) SEM image; (b) HRTEM image; (c) Crystallographic planes and interplanar spacing marked by dashed boxes in (b); (d) IFFT pattern corresponding to the selected area marked by the dashed array in (c); (e) Elemental mappings

Table S1 OER, HER, and overall water splitting performance of the FeCoNiMoCeP/C and catalysts in literature at 10 mA·cm-2

Sample	Electrolyte solvent	η_{10 OER}/ mV	η_{10 HER}/ mV	OER Tafel slope/ (mV·dec^-1)	HER Tafel slope/ (mV·dec^-1)	η_{10 overall water splitting}/V	Stability/h	Ref.
FeCoNiMoCeP/C	1.0 mol·L^-1 KOH	240	119	63.4	82.7	1.53	72	This work
NiCoFeMnCrP	1.0 mol·L^-1 KOH	270	220	52.5	94.5	1.55	24	[13]
FeNiCoMnCu@CNT	1.0 mol·L^-1 KOH+Sea water	380	290	130.0	171.0	1.60	40	[35]
CoNiCuMnAl@C 2 h	1.0 mol·L^-1 KOH+Sea water	290	-	66.8	-	1.54	30	[36]
CoCrFeNiMo	1.0 mol·L^-1 KOH	270	157	62.5	46.7	1.86	22	[37]
CoZnCdCuMnS@CF	1.0 mol·L^-1 KOH	220	173	69.8	98.5	1.63	70	[38]
La-HEO@NiFeOOH(1 : 3)	1.0 mol·L^-1 KOH	262	-	38.0	-	1.57	30	[39]

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