The microstructures of the ionomer–catalyst interfaces in the catalyst layers are important for the fuel cell performance because they determine the distribution of the active triple-phase boundaries. Here, we investigate the ionomer–catalyst interactions in hydroxide exchange membrane fuel cells (HEMFCs) using poly(aryl piperidinium) and compare them with proton exchange membrane fuel cells (PEMFCs). It is found that different catalyst layer microstructures are between the two types of fuel cell. The ionomer/carbon (I/C) ratio does not have a remarkable impact on the HEMFC performance, while it has a strong impact on the PEMFC performance, indicating the weaker interaction between the HEMFC ionomer and catalyst. Molecular dynamics simulations demonstrate that the HEMFC ionomer tends to distribute on the carbon support, unlike the PEMFC ionomer, which heavily covers the Pt nanoparticles. These results suggest that the poisoning effect of the ionomer on the catalyst is much weaker in HEMFCs, and the improved ionomer/catalyst interaction is beneficial for the HEMFC performances.

The sluggish reaction kinetics of alkaline hydrogen oxidation reaction (HOR) is one of the key challenges for anion exchange membrane fuel cells (AEMFCs). To achieve robust alkaline HOR with minimized cost, we developed a single atom-cluster multiscale structure with isolated Pt single atoms anchored on Ru nanoclusters supported on nitrogen-doped carbon nanosheets (Pt1-Ru/NC). The well-defined structure not only provides multiple sites with varied affinity with the intermediates but also enables simultaneous modulation of different sites via interfacial interaction. In addition to weakening Ru–H bond strength, the isolated Pt sites are heavily involved in hydrogen adsorption and synergistically accelerate the Volmer step with the help of Ru sites. Furthermore, this catalyst configuration inhibits the excessive occupancy of oxygen-containing species on Ru sites and facilitates the HOR at elevated potentials. The Pt1-Ru/NC catalyst exhibits superior alkaline HOR performance with extremely high activity and excellent CO-tolerance. An AEMFC with a 0.1 mg·cm_PGM⁻² loading of Pt1-Ru/NC anode catalyst achieves a peak powder density of 1172 mW·cm⁻², which is 2.17 and 1.55 times higher than that of Pt/C and PtRu/C, respectively. This work provides a new catalyst concept to address the sluggish kinetics of electrocatalytic reactions containing multiple intermediates and elemental steps.

The ordered membrane electrode assembly (MEA) has gained much attention because of its potential in improving mass transfer. Here, a comprehensive study was conducted on the influence of the patterned microporous layer (MPL) on the proton exchange membrane fuel cell performances. When patterned MPL is employed, grooves are generated between the catalyst layer and the gas diffusion layer. It is found that the grooves do not increase the contact resistance, and it is beneficial for water retention. When the MEA works under low humidity scenarios, the MEA with patterned MPL illustrated higher performance, due to the reduced inner resistance caused by improved water retention, leading to increased ionic conductivity. However, when the humidity is higher than 80% or working under high current density, the generated water accumulated in the grooves and hindered the oxygen mass transport, leading to a reduced MEA performance.

Electrochemical coupling hydrogen evolution with biomass reforming reaction (named electrochemical hydrogen and chemical cogeneration (EHCC)), which realizes green hydrogen production and chemical upgrading simultaneously, is a promising method to build a carbon-neutral society. Herein, we analyze the EHCC process by considering the market assessment. The ethanol to acetic acid and hydrogen approach is the most feasible for large-scale hydrogen production. We develop AuCu nanocatalysts, which can selectively oxidize ethanol to acetic acid (> 97%) with high long-term activity. The isotopic and in-situ infrared experiments reveal that the promoted water dissociation step by alloying contributes to the enhanced activity of the partial oxidation reaction path. A flow-cell electrolyzer equipped with the AuCu anodic catalyst achieves the steady production of hydrogen and acetic acid simultaneously in both high selectivity (> 90%), demonstrating the potential scalable application for green hydrogen production with low energy consumption and high profitability.

Ag is a potential low-cost oxygen reduction reaction (ORR) catalyst in alkaline condition, which is important for the zinc-air batteries. Here, we report that an Ag based single atom catalyst with heteroatom coordination. Ag₁-h-NPClSC, has been synthesized and shown much improved performance towards ORR by manipulating the coordination environment of the Ag center. It shows a high half wave potential (0.896 V) and a high turnover frequency (TOF) (5.9 s⁻¹) at 0.85 V, which are higher than the previously reported Ag based catalysts and commercial Pt/C. A zinc-air battery with high peak power density of 270 mW·cm⁻² is fabricated by using the Ag₁-h-NPClSC as air electrode. The high performance is attributed to (1) the hollow structure providing good mass transfer; (2) the single atom metal center structure providing high utility of the Ag; (3) heteroatom coordination environment providing the adjusted binding to the ORR intermediates. Density functional theory (DFT) calculations show that the energy barrier for the formation of OOH*, which is considered as the rate determine step for ORR on Ag nanoparticles, is lowered on Ag₁-h-NPClSC, thus improving the ORR activity. This work demonstrates that the well manipulated Ag based single atom catalysts are promising in electrocatalysis.

Electrochemical upgrading of biomass ethanol to value-added chemicals is promising for sustainable society. Here, we synthesize defective Ni₃S₂ nanowires (NWs), which show high activity towards electrochemical oxidation of ethanol to acetate. The Ni₃S₂ NWs are formed by the oriented attachment mechanism, and rich defects are introduced during the growth. A low onset potential of 1.31 V and high mass activity of 8,716 mA·mg_Ni⁻¹ at 1.5 V are achieved using the synthesized Ni₃S₂ NWs toward the ethanol electro-oxidation, which are better than the Ni(OH)₂ NWs and the Ni₃S₂ nanoparticles (NPs). And the selectivity for the acetate generation is ca. 99%. The high activity of Ni₃S₂ NWs is attributed to the easier oxidation of Ni(II) to the catalytically active Ni(III) species with the promotion from S component and rich defects. These results demonstrate that the defective NWs can be synthesized by the oriented attachment method and the defective Ni₃S₂ NWs structure as the efficient non-noble metal electrocatalysts for oxidative upgrading of ethanol.

Catalytic hydrogenation is an important process in the chemical industry. Traditional catalysts require the effective cleavage of hydrogen molecules on the metal-catalyst surface, which is difficult to achieve with non-noble metal catalysts. In this work, we report a new hydrogenation method based on water/proton reduction, which is completely different from the catalytic cleavage of hydrogen molecules. Active hydrogen species and photo-generated electrons can be directly applied to the hydrogenation process with Cu_1.94S-Zn_0.23Cd_0.77S semiconductor heterojunction nanorods. Nitrobenzene, with a variety of substituent groups, can be efficiently reduced to the corresponding aniline without the addition of hydrogen gas. This is a novel and direct pathway for hydrogenation using non-noble metal catalysts.

High performance methanol oxidation reaction (MOR) catalysts are critical to the performance of attractive, direct methanol fuel cells. Here, we use surface controlled PtNi alloy nanoparticles as model catalysts to study the MOR mechanism and give further guidance to the design of new high performance MOR catalysts. The enhanced MOR activity of PtNi alloy was mainly attributed to the enhanced OH adsorption owing to surface Ni sites. This suggests that the MOR undergoes the Langmuir–Hinshelwood mechanism, whereby adsorbed CO is removed with the assistance of adsorbed OH. Within the PtNi catalyst, Pt provides methanol adsorption sites (in which methanol is converted to adsorbed CO) and Ni provides OH adsorption sites. The optimized Pt–Ni ratio for MOR was found to be 1:1. This suggests that bifunctional catalysts with both CO and OH adsorption sites can lead to highly active MOR catalysts.