Sustainable production of hydrogen with high purity from methanol and water at low temperatures

Abstract

Carbon neutrality initiative has stimulated the development of the sustainable methodologies for hydrogen generation and safe storage. Aqueous-phase reforming methanol and H₂O (APRM) has attracted the particular interests for their high gravimetric density and easy availability. Thus, to efficiently release hydrogen and significantly suppress CO generation at low temperatures without any additives is the sustainable pursuit of APRM. Herein, we demonstrate that the dual-active sites of Pt single-atoms and frustrated Lewis pairs (FLPs) on porous nanorods of CeO₂ enable the efficient additive-free H₂ generation with a low CO (0.027%) through APRM at 120 °C. Mechanism investigations illustrate that the Pt single-atoms and Lewis acidic sites cooperatively promote the activation of methanol. With the help of a spontaneous water dissociation on FLPs, Pt single-atoms exhibit a significantly improved reforming of *CO to promote H₂ production and suppress CO generation. This finding provides a promising path towards the flexible hydrogen utilizations.

Fig. 1. Catalyst design.

a Scheme of H₂O activation on classic Lewis acid-base sites and FLPs. b Energy barrier and c adsorption configuration of H₂O activation on various actives sites. d The designed dual-active sites of single-atom Pt and FLPs. Note: The dark bule, red, and yellow balls respective the Pt, O, and Ce atoms, respectively. The abbreviation of FLP is the frustrated Lewis pairs.

Fig. 2. Characterizations of the Pt₁/PN-CeO₂ catalyst.

a HAADF-STEM image and b EDS mapping. c XANES spectra of Pt-foil, PtO₂, and Pt₁/PN-CeO₂. d The k³-weighted Fourier-transformed spectra derived from the EXAFS spectra of the Pt₁/PN-CeO₂ catalysts and PtO₂.

Fig. 3. Catalytic performance.

a H₂ generation from methanol and H₂O catalyzed by various Pt catalysts. The error is derived from three parallel experiments. Reaction conditions: catalysts (50 mg), CH₃OH (40 mL), H₂O (18 mL), n(CH₃OH):n(H₂O) = 1:1, and N₂ (0.4 MPa). b Summary of the H₂ generation catalyzed by Pt₁/PN-CeO₂ in the absence of additives compared with various reported homogeneous catalysts with or without additives at low temperature. c Cycling of Pt₁/PN-CeO₂ for H₂ generation from methanol and H₂O. The reaction time of each cycle was 1 and 3 h at 160 and 120 °C, respectively. Reaction conditions: Pt₁/PN-CeO₂ (50 mg), CH₃OH (40 mL), H₂O (18 mL), n(CH₃OH):n(H₂O) = 1:1, and N₂ (0.4 MPa).

Fig. 4. The influence of dual-active sites on the H₂ generation performance.

a Plots of TOF with surface Ce³⁺ fraction. The error is derived from three parallel experiments. b Plots of number of surface atoms per mole of Pt with Pt particle size of truncated cuboctahedron. c Plots of the normalized TOF values with Pt particle size. d The influence of Pt size and surface Ce³⁺ fraction on the selectivity of CO.

Fig. 5. Kinetic analysis of dual-active sites for H₂ generation from methanol and H₂O.

a Ratios of H₂ generation rate from CH₃OH/H₂O to CH₃OH/D₂O. b Ratios of H₂ generation rate from CH₃OH/H₂O to CD₃OD/H₂O. c H₂ generation rates at various reaction temperatures catalyzed by Pt₁/PN-CeO₂, Pt/PN-CeO₂, and Pt/NR-CeO₂. The error is derived from three parallel experiments. d E_a of various Pt catalysts for H₂ generation from methanol and H₂O.

Fig. 6. Proposed reaction process.

Catalytic pathway for H₂ generation from methanol and H₂O catalyzed by the Pt₁-FLP dual-active sites constructed on Pt₁/PN-CeO₂.