Single cluster catalysts (SCCs), which exhibit remarkable catalytic performance due to their high metal loading and synergy effect between metal atoms, have attracted great attention in research. Herein, by means of density functional theory calculations, the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) performances of precious metal (Pt, Pd, Rh, and Ir) trimetallic single-cluster electrocatalyst (U_xV_yW_z-NG) are investigated. The calculation results show that Pt, Pd, and Ir have significant effect on ORR, OER, and HER, respectively, and all the calculated U_xV_yW_z-NG structures are thermodynamically stable due to the negative formation energies and binding energies. The Pt₃-NG, Pd₃-NG, and Ir₃-NG show the lowest ORR, OER, and HER overpotentials of 0.63, 0.77, and −0.02 V, respectively, among all combinations of U_xV_yW_z-NG. These overpotentials are lower than that of precious metal single atom catalysts (SACs), which indicate better activities of precious trimetallic SCCs than those of SACs. The electronic structure reveals that the O-2p orbital shows strong hybridization strength with Pt-3d orbitals in the system of OH adsorbed Pt₃-NG and thus facilitates the electrocatalytic reactions. The results are helpful for the rational design of high-performance triatomic catalysts.

Porous membrane separation is a competitive hydrogen purification technology due to the advantages of environmental friendliness, energy-saving, simple operation, and low cost. Benefiting from the booming development of materials science and chemical science, great progress has been made in H₂ separation with porous membranes. This review focuses on the latest advances in the design and fabrication of H₂ separation inorganic microporous membranes, with emphasis on the synthetic strategies to achieve structural integrity, continuity and stability. This review starts with a brief introduction to the membrane separation mechanisms, followed by an elaboration on the synthetic challenges and corresponding solutions of various high-performance inorganic microporous membranes based on zeolites, silica, carbon, and metal-organic frameworks (MOFs). At last, by highlighting the prospects of ultrathin two-dimensional (2D) porous membranes, we wish to shed some light on the further development of new materials and membranes for highly efficient hydrogen separation.

Non-precious metal catalysts (NPMCs) are promising low-cost alternatives of Pt/C for oxygen reduction reaction (ORR), which however suffer from serious stability challenge in the devices of proton-exchange-membrane fuel cells (PEMFC). Different from the traditional strategies of increasing the degree of graphitization of carbon substrates and using less Fenton-reactive metals, we prove here that proper regulation of coordination anions is also an effective way to improve the stability of NPMC. N/P co-coordinated Fe-Co dual-atomic-sites are constructed on ZIF-8 derived carbon support using a molecular precursor of C₃₄H₂₈Cl₂CoFeP₂ and a “precursor-preselected” method. A composition of FeCoN₅P₁ is infered for the dual-atom active site by microscopy and spectroscopy analysis. By comparing with N-coordinated references, we investigate the effect of P-coodination on the ORR catalysis of Fe-Co dual-atom catalysts in PEMFC. The metals in FeCoN₅P₁ have the lower formation energy than those in the solo N-coordinated active sites of FeCoN₆ and FeN₄, and exhibits a much better fuel cell stability. This anion approach provides a new way to improve the stability of dual-atom catalysts.

Carbon-supported transition metal single atoms are promising oxygen reduction reaction (ORR) electrocatalyst. Since there are many types of carbon supports and transition metals, the accurate prediction of the components with high activity through theoretical calculations can greatly save experimental time and costs. In this work, the ORR catalytic properties of 180 types single-atom catalysts (SACs) composed of the eight representative carbon-based substrates (graphdiyne, C₂N, C₃N₄, phthalocyanine, C-coordination graphene, N-coordination graphene, covalent organic frameworks and metal-organic frameworks) and 3d, 4d, and 5d transition metal elements are investigated by density functional theory (DFT). The adsorption free energy of OH* is proved a universal descriptor capable of accurately prediction of the ORR catalytic activity. It is found that the oxygen reduction reaction overpotentials of all the researched SACs follow one volcano shape very well with the adsorption free energy of OH*. Phthalocyanine, N-coordination graphene and metal-organic frameworks stand out as the promising supports for single metal atom due to the relatively lower overpotentials. Notably, the Co-doped metal-organic frameworks, Ir-doped phthalocyanine, Co-doped N-coordination graphene, Co-doped graphdiyne and Rh-doped phthalocyanine show extremely low overpotentials comparable to that of Pt (111). The study provides a guideline for design and selection of carbon-supported SACs toward oxygen reduction reaction.

Due to the high specific surface area, abundant nitrogen and micropores, ZIF-8 is a commonly used precursor for preparing high performance Fe-N-C catalysts. However, the Zn element is inevitably remained in the prepared Fe-N-C catalyst. Whether the residual Zn element affects the catalytic activity and active site center of the Fe-N-C catalyst caused widespread curiosity, but has not been studied yet. Herein, we built several Fe, Zn, and N co-doped graphene models to investigate the effect of Zn atoms on the electrocatalytic performance of Fe-N-C catalysts by using density functional theory method. The calculation results show that all the calculated Fe-Zn-N_x structures are thermodynamically stable due to the negative formation energies and relative stabilities. The active sites around Fe and Zn atoms in the structure of Fe-Zn-N₆(III) show the lowest oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) overpotentials of 0.38 and 0.43 V, respectively. The bridge site of Fe-Zn in Fe-Zn-N₅ shows the lowest η^HER of −0.26 V. A few structures with a better activity than that of FeN₄ or ZnN₄ are attributed to the synergistic effects between Fe and Zn atoms. The calculated ORR reaction pathways on Fe-Zn-N₆(III) show that H₂O is the final product and the ORR mechanism on the catalyst would be a four-electron process, and the existence of Zn element in the Fe-N-C catalysts plays a key role in reducing the ORR activation energy barrier. The results are helpful for the deep understand of high-performance Fe-N-C catalysts.

Catalysts play a critical role in improving the hydrogen storage kinetics in Mg/MgH₂ system. Exploring highly efficient catalysts and catalyst design principles are hot topics but challenging. The catalytic activity of metallic elements on dehydrogenation kinetics generally follows a sequence of Ti > Nb > Ni > V > Co > Mo. Herein, we report a highly efficient alloy catalyst composed of low-active elements of Mo and Ni (i.e. MoNi alloy) for MgH₂ particles. MoNi alloy nanoparticles show excellent catalytic effect, even outperforming most advanced Ti-based catalysts. The synergy between Mo and Ni elements can promote the break of Mg-H bonds and the dissociation of hydrogen molecules, thus significantly improves the kinetics of Mg/MgH₂ system. The MoNi-catalyzed Mg/MgH₂ system can absorb and release 6.7 wt.% hydrogen within 60 s and 10 min at 300 ^oC, respectively, and exhibits excellent cycling stability and low-temperature hydrogen storage performance. This study provides a strategy for designing efficient catalysts for hydrogen storage materials using the synergy of metal elements.

Design and synthesis of highly efficient and cost-effective bifunctional catalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) remain a big challenge. Herein, a quaternary amorphous nanocompound Ni-Fe-P-B has been synthesized by a facile, scalable co-reduction method. The Ni-Fe-P-B exhibits high electrocatalytic activity and outstanding durability for both HER and OER, delivering a current density of 10 mA·cm^-2 at overpotentials of 220 and 269 mV, respectively. When loaded on carbon fiber paper (CFP) as a bifunctional catalyst, the Ni-Fe-P-B@CFP electrode requires a low cell voltage of 1.58 V to obtain 10 mA·cm^-2 for overall water splitting with negligible recession over 60 h. The excellent catalytic performances of Ni-Fe-P-B mainly benefit from the metal-metalloid combined composition modulation and the unique amorphous structure. This work provides new insights into the design of robust bifunctional catalysts for water splitting, and may promote the development of multicomponent amorphous catalysts.