Maximizing Metal-Support Interactions in Pt/Co3O4 Nanocages to Simultaneously Boost Hydrogen Production Activity and Durability

Construction of Ultrafine PtIr Clusters Supported on Co3O4 Nanoflowers for Enhanced Overall Water Splitting

Green hydrogen production through electrochemical overall water splitting has suffered from sluggish oxygen evolution reaction (OER) kinetics, inferior conversion efficiency, and high cost. Herein, ultrafine PtIr clusters are synthesized via an electrodeposition method and decorated on the Co3O4 nanoflowers assembled by nanowires (PtIr-Co3O4). The encouraging performances in electrochemical OER and hydrogen evolution reaction (HER) are achieved over the PtIr-Co3O4 catalyst, with the overpotentials as low as 410 and 237 mV at 100 mA cm-2, respectively, outperforming the commercial IrO2 and Pt/C catalysts. Due to the ultralow loading of PtIr clusters, the PtIr-Co3O4 catalyst exhibits 1270 A gIr -1 for OER at the overpotential of 400 mV. Our detailed analyses also show that the strong interactions between the ultrafine PtIr clusters and the Co3O4 nanoflowers enable the PtIr-Co3O4 catalyst to afford 10 mA cm-2 for the overall water splitting at the potential of 1.57 V, accompanied by high durability for 100 h.

Atomic-Level Tailoring of the Electronic Metal-Support Interaction Between Pt-Co3O4 Interfaces for High Hydrogen Evolution Performance

Atomic-level modulation of the metal-oxide interface is considered an effective approach to optimize the electronic structure and catalytic activity of metal catalysts but remains highly challenging. Here, we employ the atomic layer deposition (ALD) technique together with a heteroatom doping strategy to effectively tailor the electronic metal-support interaction (EMSI) at the metal-oxide interface on the atomic level, thereby achieving high hydrogen evolution performance and Pt utilization. Theoretical calculations reveal that the doping of N atoms in Co3O4 significantly adjusts the EMSI between Pt-Co3O4 interfaces and, consequently, alters the d-band center of Pt and optimizes the adsorption/desorption of reaction intermediates. This work sheds light on the atomic-level regulation and mechanistic understanding of the EMSI in metal-oxide, while providing guidance for the development of advanced EMSI electrocatalysts for various future energy applications.

Rare-Earth-Modified Metal-Organic Frameworks and Derivatives for Photo/Electrocatalysis

Metal-organic frameworks (MOFs) and their derivatives have attracted much attention in the field of photo/electrocatalysis owing to their ultrahigh porosity, tunable properties, and superior coordination ability. Regulating the valence electronic structure and coordination environment of MOFs is an effective way to enhance their intrinsic catalytic performance. Rare earth (RE) elements with 4f orbital occupancy provide an opportunity to evoke electron rearrangement, accelerate charged carrier transport, and synergize the surface adsorption of catalysts. Therefore, the integration of RE with MOFs makes it possible to optimize their electronic structure and coordination environment, resulting in enhanced catalytic performance. In this review, progress in current research on the use of RE-modified MOFs and their derivatives for photo/electrocatalysis is summarized and discussed. First, the theoretical advantages of RE in MOF modification are introduced, with a focus on the roles of 4f orbital occupancy and RE ion organic coordination ligands. Then, the application of RE-modified MOFs and their derivatives in photo/electrocatalysis is systematically discussed. Finally, research challenges, future opportunities, and prospects for RE-MOFs are also discussed.

Cobalt-Promoted Noble-Metal Catalysts for Efficient Hydrogen Generation from Ammonia Borane Hydrolysis

Ammonia borane (AB) has been regarded as a promising material for chemical hydrogen storage. However, the development of efficient, cost-effective, and stable catalysts for H₂ generation from AB hydrolysis remains a bottleneck for realizing its practical application. Herein, a step-by-step reduction strategy has been developed to synthesize a series of bimetallic species with small sizes and high dispersions onto various metal oxide supports. Superior to other non-noble metal species, the introduction of Co species can remarkably and universally promote the catalytic activity of various noble metals (e.g., Pt, Rh, Ru, and Pd) in AB hydrolysis reactions. The optimized Pt_0.1%Co_3%/TiO₂ catalyst exhibits a superhigh H₂ generation rate from AB hydrolysis, showing a turnover frequency (TOF) value of 2250 mol_H2 mol_Pt^-1 min^-1 at 298 K. Such a TOF value is about 10 and 15 times higher than that of the monometal Pt/TiO₂ and commercial Pt/C catalysts, respectively. The density functional theory (DFT) calculation reveals that the synergy between Pt and CoO species can remarkably promote the chemisorption and dissociation of water molecules, accelerating the H₂ evolution from AB hydrolysis. Significantly, the representative Pt_0.25%Co_3%/TiO₂ catalyst exhibits excellent stability, achieving a record-high turnover number of up to 215,236 at room temperature. The excellent catalytic performance, superior stability, and low cost of the designed catalysts create new prospects for their practical application in chemical hydrogen storage.

Modulating the Acidic Properties of Mesoporous Mox-Ni0.8Cu0.2O Nanowires for Enhanced Catalytic Performance toward the Methanolysis of Ammonia Borane for Hydrogen Production

Rational construction of inexpensive, highly efficient, and stable catalysts for ammonia borane (AB) methanolysis is in high demand but still remains a great challenge. In this work, we have successfully fabricated uniform Mo_x-Ni_0.8Cu_0.2O nanowires using a simple hydrothermal method followed by a post-calcination treatment and flexibly modulated the acidity of their surface by changing the amount of Mo introduced into Ni_0.8Cu_0.2O. The Mo_0.1-Ni_0.8Cu_0.2O catalyst displayed strong catalytic activity toward AB methanolysis with an ultrahigh turnover frequency of 46.9 mol_H2 mol_cat.^-1 min^-1, which is even higher than some noble metal catalysts. In this work, an equation regarding the relationship between the quantity of moderated acid sites of catalysts and its corresponding activity toward AB methanolysis was first determined. A plausible mechanism for AB methanolysis catalyzed by Mo_x-Ni_0.8Cu_0.2O was proposed, and the benefits of the introduction of MoO₃ to Ni_0.8Cu_0.2O for enhancing the catalytic performance were also discussed. These findings can form a basis for the rational construction of inexpensive catalysts with robust performance toward AB methanolysis for hydrogen production.

Nanoengineering of Catalysts for Enhanced Hydrogen Production

Hydrogen (H2) has emerged as a sustainable energy carrier capable of replacing/complementing the global carbon-based energy matrix. Although studies in this area have often focused on the fundamental understanding of catalytic processes and the demonstration of their activities towards different strategies, much effort is still needed to develop high-performance technologies and advanced materials to accomplish widespread utilization. The main goal of this review is to discuss the recent contributions in the H2 production field by employing nanomaterials with well-defined and controllable physicochemical features. Nanoengineering approaches at the sub-nano or atomic scale are especially interesting, as they allow us to unravel how activity varies as a function of these parameters (shape, size, composition, structure, electronic, and support interaction) and obtain insights into structure–performance relationships in the field of H2 production, allowing not only the optimization of performances but also enabling the rational design of nanocatalysts with desired activities and selectivity for H2 production. Herein, we start with a brief description of preparing such materials, emphasizing the importance of accomplishing the physicochemical control of nanostructures. The review finally culminates in the leading technologies for H2 production, identifying the promising applications of controlled nanomaterials.

Metal-Support Synergistic Catalysis in Pt/MoO3-x Nanorods toward Ammonia Borane Hydrolysis with Efficient Hydrogen Generation

Ammonia borane (NH₃BH₃, AB) serves as a promising material for chemical storage of hydrogen owing to its high hydrogen density and superior stability, in which the development of highly efficient heterogeneous catalysts toward AB hydrolysis plays a crucial role. Herein, we report Pt atomic clusters supported on MoO_3-x nanorods using a two-step process: MoO_3-x nanorods were synthesized at various calcination temperatures, followed by a further deposition-precipitation approach to obtain Pt/MoO_3-x catalysts (denoted as Pt/MoO_3-x-T, T = 300, 400, 500, and 600 °C). The optimized Pt/MoO_3-x-500 catalyst exhibits a prominent catalytic performance toward hydrolytic dehydrogenation of AB for H₂ generation, with a turnover frequency value of 2268.6 min^-1, which stands at the top level among the reported catalysts. Moreover, the catalyst shows a remarkable stability with 90% activity remaining after five cycles. A combination investigation including HR-TEM, ac-HAADF-STEM, XPS, in situ CO-IR, XANES, and Bader charge analysis verifies the formation of Pt²⁺-O_v-Mo⁵⁺ (O_v represents oxygen vacancy), whose concentration is dependent on the strength of the metal-support interaction. Studies on the structure-property correlation based on an isotopic kinetic experiment, in situ FT-IR, and DFT calculations further reveal that the Mo⁵⁺-O_v sites accelerate the dissociation of H₂O molecules (rate-determining step), while the adjacent Pt²⁺ species facilitates the cleavage of the B-H bond in the AB molecule to produce H₂. This work provides a fundamental and systematic understanding on the metal-support synergistic catalysis toward robust H₂ production, which is constructive for hydrogen storage and energy catalysis.