Ambient hydrogenation of solid aromatics enabled by a high entropy alloy nanocatalyst

Hydrogenation is a versatile chemical process with significant applications in various industries, including food production, petrochemical refining, pharmaceuticals, and hydrogen carriers/safety. Traditional hydrogenation of aromatics, hindered by the stable π-conjugated phenyl ring structures, typically requires high temperatures and pressures, making ambient hydrogenation a grand challenge. Herein, we introduce a PdPtRuCuNi high entropy alloy (HEA) nanocatalyst, achieving an exceptional 100% hydrogenation of carbon-carbon unsaturated bonds, including alkynyl and phenyl groups, in solid 1,4-bis(phenylethynyl)benzene (DEB) at 25 °C under ≤1 bar H2 and solventless condition. This results in a threefold higher hydrogen uptake for DEB-contained composites compared to conventional Pd catalysts, which can only hydrogenate the alkynyl groups with a ~ 27% conversion of DEB. Our experimental results, complemented by theoretical calculations, reveal that PdPtRu alloy is highly active and crucial in enabling the hydrogenation of phenyl groups, while all five elements work synergistically to regulate the reaction rate. Remarkably, this newly developed catalyst also achieves nearly 100% reactivity for ambient hydrogenation of a broad range of aromatics, suggesting its universal effectiveness. Our research uncovers a novel material platform and catalyst design principle for efficient and general hydrogenation. The multi-element synergy in HEA also promises unique catalytic behaviors beyond hydrogenation applications.

The maximum hydrogen uptake capacities.c 1 H NMR spectra of DEB before and after hydrogenation.d The transformation of the DEB molecule from the original structure to the final hydrogenated products catalyzed by PdPtRu-contained catalysts.
Supplementary Figure.3 XPS full spectra of PdPtRuCuNi/CNFs.Supplementary Fig. 4 The characterization of X-ray near-side absorption.a-c The X-ray absorption near edge structure (XANES) spectra of PdPtRuCuNi/CNFs and monometal.a The Pt L3-edge.b The Cu K-edge.c The Ni K-edge.d-f Fourier transform EXAFS spectra of PdPtRuCuNi/CNFs and monometal.d Pt. e Cu. f Ni.

4 Supplementary Fig. 5 . 7 . 8
The morphology of Pd/CNFs-DEB composites before and after hydrogenation.a, c The digital images.b, d SEM images.Supplementary Fig. 6 The morphology and element distribution of PdPtRuCuNi/CNFs-DEB composites before and after hydrogenation.a, d The digital images.b, e SEM images.c, f Element mapping of Pd, Pt, Ru, Cu, Ni, C and O.The Pd/CNFs-DEB composite (Supplementary Figure 5) is the loose powder before and after hydrogenation, while the PdPtRuCuNi/CNFs-DEB changes from loose powder to melt after hydrogenation.The catalytic hydrogenation by different catalysts including PdPtRuCuNi/CNFs, Pd/CNFs, the commercial Pd/C, and Pt/C.a The hydrogen uptake curves with time.b 13 C and c 1 H NMR of DEB before and after hydrogenation.d The conversion of C-C unsaturated bonds (alkynyl and phenyl groups) in the hydrogenated DEB molecules.The hydrogenation of PdPtRuCuNi/CNFs-DEB at different temperatures.a Absorption and desorption curves with pressure (absorption: 0-1 bar, desorption 1-0 bar).b The final amount of hydrogen uptake.c 13 C and d 1 H NMR of DEB before and after hydrogenation.e The conversion of C-C unsaturated bonds (alkynyl and phenyl groups) in the hydrogenated DEB molecules.13 The TEM characterization of PdPtRuCu/CNFs. a TEM morphology.b HRTEM image.c Selective electron diffraction pattern.d EDS mapping.The EDS mapping indicates that the Pd, Pt, Ru, and Cu elements distribute uniformly on the nanoparticles.Supplementary Fig. 14 The TEM characterization of PdPtRuNi/CNFs. a TEM morphology.b HRTEM image.c Selective electron diffraction pattern.d EDS mapping.The EDS mapping indicates that the Pd, Pt, Ru, and Ni elements distribute uniformly on the nanoparticles.
The hydrogen uptake curves (dot line) and reaction rates (slopes) of DEB with time.b

. 21 Supplementary Fig. 22 a
The XRD patterns of PdPtRu/CNFs catalyst.The PdPtRu catalyst is a single-phase alloy.H 1 , and b 13 C NMR spectra of DEB before and after hydrogenation.c The conversion of C-C unsaturated bonds (alkynyl and phenyl groups) in the hydrogenated DEB molecules.

20 Supplementary Fig. 27 23 .
absorption of H2 molecules on the surface of PdPtRuCuNi HEA (111) calculated on 192 hollow-and 288 bridge-sites (480 sites in all).a The absorption energy.b The H-H bond distance activated by PdPtRuCuNi HEAs.c The distribution of final H heights to the surface of PdPtRuCuNi HEA(111).d,e The relationship of final H-H distance and H height with absorption energy.The spatial variation of ∆ −  on the six different slabs of PdPtRuCuNi HEA (111).The circles represent the hollow sites, and hexagons represent the bridge sites.The surface atomic arrangements see Supplementary Fig. Every slab has 32 hollow sites and 48 bridge sites for H2, the color of sites is darker, indicating the stronger adsorption.Every slab has the sites favorable for hydrogen absorption.

Supplementary Fig. 29 23 .Supplementary Fig. 30 a
The spatial variation of ∆Eads-PhA on the six different slabs of PdPtRuCuNi HEA (111).The surface atomic arrangements see Supplementary Fig. Every slab has 32 hollow sites to absorb the PhA molecules, the color of sites became darker, indicating the adsorption of PhA more stonger.Every slab has the sites favorable for PhA absorption.The increased C-C bond distance of alkynyl and phenyl groups activated by Pd (line) and PdPtRuCuNi HEA (histogram) catalysts.b The height of alkynyl and phenyl groups to the surface of Pd (111) and PdPtRuCuNi HEA (111) after activated.

Supplementary Fig. 32 a
13 C and b 1 H NMR spectra of toluene before and after hydrogenation by PdPtRuCuNi HEA/CNFs, c 1 H NMR spectra of toluene catalyzed by the same PdPtRuCuNi HEAs with four times continuously, d The stable catalytic activity of PdPtRuCuNi HEAs for toluene.Reaction condition: 40 mg PdPtRuCuNi HEA/CNFs, 3 mL toluene, 25 ℃, 10 bar H2, 10 h.

b 1 H
NMR spectra of diphenylacetylene before and after hydrogenation.e The conversion at different hydrogen pressure.c 13 C and d 1 H NMR spectra of diphenylacetylene before and after hydrogenation.f The conversion at different amount of catalyst.

Pd Pt Ru Cu (111) 2.15 Å 50 nm 100 nm 10 nm a b c 5 nm -1 d Pd Ni Pt Ru a b c 100 nm 10 nm 5 nm -1 (111) 2.17 Å d 50 nm Supplementary Fig. 15 The XPS results of PtRuCuNi/CNFs. a Survey
Cu 2p high-resolution spectra.The Pd, Pt, Ru and Cu exist mainly in their zero-valence states.Ni 2p high-resolution spectra.The Pd, Pt, Ru exist mainly in their zero-valence states, the zero-valence state and oxidation state coexist for Ni.
Supplementary Fig. 16 The XPS results of PdRuCuNi/CNFs. a Survey spectra.b Pd 3d, c Ru 3p, d Cu 2p, and e Ni 2p high-resolution spectra.The Pd, Ru, Cu exist mainly in their zero-valence states, the zerovalence state and oxidation state coexist for Ni.Supplementary Fig. 17 The XPS results of PdPtCuNi/CNFs. a Survey spectra.b Pd 3d, c Pt 4f, d Cu 2p, and e Ni 2p high-resolution spectra.The Pd, Pt, Cu exist mainly in their zero-valence states, the zerovalence state and oxidation state coexist for Ni. 13 Supplementary Fig. 18 The XPS results of PdPtRuCu/CNFs. a Survey spectra.b Pd 3d, c Pt 4f, d Ru 3p, and e Supplementary Fig. 19 The XPS results of PdPtRuNi/CNFs. a Survey spectra.b Pd 3d, c Pt 4f, d Ru 3p, and e