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Abstract The serious problem of carbon monoxide (CO) poisoning on the surface of Pt-based catalysts has long constrained the commercialization of proton exchange membrane fuel cells (PEMFCs). Regeneration of Pt sites by maintaining CO scavenging ability through precise construction of the surface and interface structure of the catalyst is the key to obtaining high-performance CO-resistant catalysts. Here, we used molybdenum carbide (MoCx) as the support for Pt and introduced Ru single atoms (SA-Ru) at the Pt-MoCx interface to jointly decrease the CO adsorption strength on Pt. More importantly, the MoCx and SA-Ru are immune to CO poisoning, which continuously assists in the oxidation of adsorbed CO by generating oxygen species from water dissociation. These two effects combine to confer this anode catalyst (SA-Ru@Pt/MoCx) remarkable CO tolerance and the ability to operate stably in fuel cell with high CO concentration (power output 85.5 mW cm−2@20,000 ppm CO + H2 – O2), making it possible to directly use the cheap reformed hydrogen as the fuel for PEMFCs.

Abstract Ruthenium dioxide is presently the most active catalyst for the oxygen evolution reaction (OER) in acidic media but suffers from severe Ru dissolution resulting from the high covalency of Ru-O bonds triggering lattice oxygen oxidation. Here, we report an interstitial silicon-doping strategy to stabilize the highly active Ru sites of RuO2 while suppressing lattice oxygen oxidation. The representative Si-RuO2−0.1 catalyst exhibits high activity and stability in acid with a negligible degradation rate of ~52 μV h−1 in an 800 h test and an overpotential of 226 mV at 10 mA cm−2. Differential electrochemical mass spectrometry (DEMS) results demonstrate that the lattice oxygen oxidation pathway of the Si-RuO2−0.1 was suppressed by ∼95% compared to that of commercial RuO2, which is highly responsible for the extraordinary stability. This work supplied a unique mentality to guide future developments on Ru-based oxide catalysts’ stability in an acidic environment.

Bimetallic Pt-skin catalyst is a class of near-surface alloy (NSA) that owns a high degree of control over composition. Herein, density functional theory (DFT) is used to calculate the energetics of oxygen reduction reaction (ORR) on Pt-skin over Ir, Pd and Au substrates. A Brønsted-Evans-Polanyi (BEP) relationship can be determined for the oxygen molecule dissociation. The binding energy of both atomic oxygen and hydroxyl radical is found to correlate well with the d band center of Pt-skin atoms. Their catalytic activities show the volcano relationship as the positions of each substrate in the periodic table. The effect of surface strain, band structure and charge transfer on the d band center is well studied, and it can be found that the surface strain effect plays a dominant role for all Pt-skin catalysts. Ir substrate makes the d band center of Pt-skin go far away from the Fermi level, while Au substrate makes it move towards the Fermi level. Being different from both Ir and Au, Pd substrate makes the d band center of Pt-skin comparable with the monometallic Pt.

The Chinese iron pan can function as a nonstick pan even without a polytetrafluoroethylene (PTFE) coating after a “Kitchen God blessing” seasoning process. We simulate this process and disclose the science behind the “Kitchen God blessing,” finding that through repeated oil-coating and heating, the reversible insertion and extraction of oxygen atoms split the surface of the iron pan, gradually producing Fe3O4 nanoballs. These balls give the iron pan a conditional hydrophobicity property, meaning the pan would be hydrophilic when the ingredients contain much water and hydrophobic when they contain less water. The former enables heat to be transferred rapidly through the nanoballs while the latter slows down the heat transference and prevents the pan from sticking. This discovery provides an approach of generating nanoballs on the surface of the metal and also discloses the secret of the fantastic taste produced by cooking with a Chinese iron pan.

Even though various nickel–nitrogen–carbon (Ni-N-C) combinations are prospective low-cost catalysts for the CO2 electroreduction reaction (CO2RR), which is one avenue for attaining carbon neutrality, the detailed role of different N species has hardly been investigated. Here, we report a hollow porous N-doped carbon nanofiber with NiNX-pyridinic N active species (denoted as h-Ni-N-C) developed using a facile electrospinning and SiO2 space-confined pyrolysis strategy. The NiNX-pyridinic N species are facilely generated during the pyrolysis process, giving rise to enhanced activity and selectivity for the CO2RR. The optimized h-Ni-N-C exhibits a high CO Faradaic efficiency of 91.3% and a large current density of −15.1 ​mA ​cm−2 ​at −0.75 ​V versus reversible hydrogen electrode in an H-cell. Density functional theory (DFT) results show that NiN4-pyridinic N species demonstrate a lower free energy for the catalyst's rate-determining step than isolated NiN4 and pyridinic N species, without affecting the desorption of CO∗ intermediate.

The most promising energy storage devices are lithium-sulfur batteries (LSBs), which offer a high theoretical energy density that is five times greater than that of lithium-ion batteries. However, there are still significant barriers to the commercialization of LSBs, and mesoporous carbon-based materials (MCBMs) have attracted much attention in solving LSBs’ problems, due to their large specific surface area (SSA), high electrical conductivity, and other unique advantages. The synthesis of MCBMs and their applications in the anodes, cathodes, separators, and “two-in-one” hosts of LSBs are reviewed in this study. Most interestingly, we establish a systematic correlation between the structural characteristics of MCBMs and their electrochemical properties, offering recommendations for improving performance by altering the characteristics. Finally, the challenges and opportunities of LSBs under current policies are also clarified. This review provides ideas for the design of cathodes, anodes, and separators for LSBs, which could have a positive impact on the performance enhancement and commercialization of LSBs. The commercialization of high energy density secondary batteries is of great importance for the achievement of carbon neutrality and to meet the world’s expanding energy demand.

In the context of the current serious problems related to energy demand and climate change, substantial progress has been made in developing a sustainable energy system. Electrochemical hydrogen–water conversion is an ideal energy system that can produce fuels via sustainable, fossil-free pathways. However, the energy conversion efficiency of two functioning technologies in this energy system—namely, water electrolysis and the fuel cell—still has great scope for improvement. This review analyzes the energy dissipation of water electrolysis and the fuel cell in the hydrogen–water energy system and discusses the key barriers in the hydrogen- and oxygen-involving reactions that occur on the catalyst surface. By means of the scaling relations between reactive intermediates and their apparent catalytic performance, this article summarizes the frameworks of the catalytic activity trends, providing insights into the design of highly active electrocatalysts for the involved reactions. A series of structural engineering methodologies (including nanoarchitecture, facet engineering, polymorph engineering, amorphization, defect engineering, element doping, interface engineering, and alloying) and their applications based on catalytic performance are then introduced, with an emphasis on the rational guidance from previous theoretical and experimental studies. The key scientific problems in the electrochemical hydrogen–water conversion system are outlined, and future directions are proposed for developing advanced catalysts for technologies with high energy-conversion efficiency.

A high-performance anion exchange membrane (AEM) is critical for the development of alkaline fuel cell. In this work, AEMs with an interpenetrating polymer network (IPN) are synthesized. An electron microscope clearly reveals a highly efficient “ion channel” network, which is constructed with a small amount of cation exchange groups. This specially designed ion channel leads to extraordinary hydroxide conductivity (e.g., 257.8 mS cm-1 at 80 °C) of IPN AEMs at moderate ion exchange capacity (IEC=1.75 mmol g−1), as well as excellent long-term alkaline stability at harsh condition which showed that 81% of original conductivity can be retained after a long time for 1248 hours. Moreover, a remarkable peak power density of 1.20 W cm-2 (0.1 MPa backpressure) with nonprecious metal (FeNx-CNTs) as oxygen reduction reaction (ORR) catalyst in a fuel cell test was achieved. This work offers a general strategy to prepare high-performance AEMs based on IPN structure design.

Abstract Ag–AgX(X = Cl, Br)@TiO2 nanoparticle-aggregated spheres with different mass ratio of R = TiO2/Ag(X) from 35:1 to 5:1 were synthesized by a facile sol–gel technique with post-photoreduction. The photocatalytic activities of both Ag–AgCl@TiO2 and Ag–AgBr@TiO2 under visible light are effectively improved by ~3 times relative to TiO2 NPAS under the simulated sunlight for the decomposition of methyl orange (MO). Ag–AgBr@TiO2 showed 30% improvement and less stable in photocatalytic activity than that of AgCl@TiO2. The role of Ag and AgX nanoparticles on the surface of Ag–AgX(X = Cl, Br)@TiO2 was discussed. Ag on these samples not only can efficiently harvest visible light especially for AgCl, but also efficiently separate excited electrons and holes via the fast electron transfer from AgX(X = Cl, Br) to metal Ag nanoparticles and then to TiO2-aggregated spheres on the surface of heterostructure. On the basis of their efficient and stable photocatalytic activities under visible-light irradiation, these photocatalysts could be widely used for degradation of organic pollutants in aqueous solution.

At present, despite the great advances in polymer electrolyte membrane fuel cell (PEMFC) technology over the past two decades through intensive research and development activities, their large-scale commercialization is still hampered by their higher materials cost and lower reliability and durability. In this review, water management is given special consideration. Water management is of vital importance to achieve maximum performance and durability from PEMFCs. On the one hand, to maintain good proton conductivity, the relative humidity of inlet gases is typically held at a large value to ensure that the membrane remains fully hydrated. On the other hand, the pores of the catalyst layer (CL) and the gas diffusion layer (GDL) are frequently flooded by excessive liquid water, resulting in a higher mass transport resistance. Thus, a subtle equilibrium has to be maintained between membrane drying and liquid water flooding to prevent fuel cell degradation and guarantee a high performance level, which is the essential problem of water management. This paper presents a comprehensive review of the state-of-the-art studies of water management, including the experimental methods and modeling and simulation for the characterization of water management and the water management strategies. As one important aspect of water management, water flooding has been extensively studied during the last two decades. Herein, the causes, detection, effects on cell performance and mitigation strategies of water flooding are overviewed in detail. In the end of the paper the emphasis is given to: (i) the delicate equilibrium of membrane drying vs. water flooding in water management; (ii) determining which phenomenon is principally responsible for the deterioration of the PEMFC performance, the flooding of the porous electrode or the gas channels in the bipolar plate, and (iii) what measures should be taken to prevent water flooding from happening in PEMFCs.