The global energy and environmental crisis necessitates sustainable hydrogen (H₂) generation and storage technologies. Hydrogen's high calorific value makes it a clean energy resource, but its flammability, explosiveness, and high liquefaction pressure pose significant challenges for transportation and storage. Liquid organic hydrogen carriers offer a solution, with methanol (CH₃OH) being a promising candidate due to its sustainability, low cost, ready availability (from biomass or CO₂ hydrogenation), high gravimetric H₂ density (18.8 wt%), and safe handling. While homogeneous catalytic systems can achieve H₂ release below 100 °C, they often require strong bases (e.g., KOH, NaOH). Heterogeneous catalysts offer an environmentally friendlier approach but typically require high temperatures (≥250 °C) and produce H₂ with high CO impurities. This research aims to develop a high-efficiency catalyst for low-temperature H₂ generation from APRM with minimal CO production, moving closer to a methanol economy.

Existing methods for hydrogen production from methanol and water often face limitations. Homogeneous metal catalysts, while effective at low temperatures, typically necessitate the use of strong bases, which compromises sustainability and economic viability. Heterogeneous catalysts, such as those based on Pt, Ru, and Pd, have been explored as additive-free alternatives but suffer from the need for high reaction temperatures (above 250°C) and low hydrogen purity due to significant CO formation. Recent advancements have lowered operating temperatures to 150°C using atomically dispersed Pt on α-MoC, but further reductions while maintaining efficiency remain a challenge. The pursuit of efficient, low-temperature, additive-free catalysts with high H₂ selectivity is crucial for practical hydrogen production.

This study designed a catalyst consisting of dual-active sites: Pt single-atoms and frustrated Lewis pairs (FLPs) on porous ceria nanorods (Pt₁/PN-CeO₂). Density Functional Theory (DFT) calculations guided the catalyst design, predicting that Pt single-atoms effectively activate CH₃OH while FLPs, formed by adjacent Ce³⁺ (Lewis acid) and lattice oxygen (Lewis base) sites on CeO₂, efficiently activate H₂O. DFT calculations confirmed the synergistic effect of the dual-active sites in promoting both CH₃OH and H₂O activation and reducing the energy barrier for CO reforming. The Pt₁/PN-CeO₂ catalyst was synthesized via a two-step hydrothermal process to create porous CeO₂ nanorods, followed by photo-assisted deposition of Pt single-atoms. Catalyst characterization employed techniques such as TEM, HAADF-STEM, EDS mapping, XANES, EXAFS, DRIFTS, and XPS to confirm the successful synthesis of the dual-active site catalyst. Catalytic performance was evaluated in a closed system under N₂ (0.4 MPa) at various temperatures, measuring H₂ generation rates and CO selectivity. Control experiments using Pt nanoparticles supported on different oxides (Al₂O₃, TiO₂, C) and CeO₂ with varying degrees of porosity and surface defects were conducted to assess the contribution of the dual-active sites. Isotopic labeling experiments (H/D exchange) were used to investigate the reaction mechanism. Further DFT calculations explored the activation of CH₃OH on different catalytic models to understand the role of the dual-active sites.

The Pt₁/PN-CeO₂ catalyst demonstrated superior performance compared to other catalysts tested. At 120 °C, it achieved a turnover frequency (TOF) of 33 h⁻¹, comparable to or exceeding many homogeneous and heterogeneous catalysts, even those using additives. CO selectivity was remarkably low (<0.03%). At 135 °C, the H₂ generation rate reached 199 molH₂ molPt⁻¹ h⁻¹, significantly higher than the rates observed with Pt nanoparticles on other supports. The catalyst displayed good stability, maintaining high activity and low CO selectivity over multiple reaction cycles at both 120 and 165 °C. Control experiments confirmed the synergistic contribution of both Pt single-atoms and FLP sites to catalytic activity. The TOF increased linearly with increasing surface Ce³⁺ fraction (indicating FLP density). Isotopic labeling experiments revealed that the dual-active sites kinetically favor both CH₃OH and H₂O activation. DFT calculations showed that the energy barrier for CH₃OH decomposition was significantly lower on the Pt₁/CeO₂(110)-FLP model compared to Pt(111) or Pt₁/CeO₂(110), highlighting the synergistic effect of the dual sites. The interfacial Pt atoms in nanoparticles, rather than corner, edge, (100), or (111) atoms, were identified as the primary active sites.

The findings directly address the research question by demonstrating the effectiveness of the dual-active site catalyst in achieving high-purity H₂ generation from APRM at low temperatures without additives. The significantly enhanced catalytic activity and suppressed CO formation are attributed to the synergistic cooperation between Pt single-atoms and FLPs. Pt single-atoms facilitate CH₃OH activation, while FLPs promote H₂O dissociation and CO reforming, resulting in a low-energy pathway for H₂ production. The results contribute to the field by providing a novel and sustainable approach to H₂ generation, overcoming the limitations of existing methods. The high activity at low temperatures and the remarkable CO suppression represent significant advancements toward practical H₂ production from methanol.

This study successfully developed a highly efficient dual-active site catalyst (Pt₁/PN-CeO₂) for low-temperature H₂ generation from methanol and water. The catalyst's superior performance is attributed to the synergistic effect of Pt single-atoms and FLPs, enabling efficient activation of both reactants and effectively suppressing CO formation. Future research could focus on further optimization of the catalyst structure and exploring its applicability in various H₂ production systems. Scaling up the synthesis process for industrial applications is also a key next step.

While the catalyst showed excellent performance, the study was conducted under specific conditions. The long-term stability under continuous operation at industrial scales remains to be fully investigated. Further research is needed to optimize the catalyst for different methanol concentrations and explore the potential for deactivation due to poisoning or sintering of the Pt atoms. The current CO concentration (270 ppm) may still require further purification for certain applications.