Ni-based catalysts, as non-noble metal alternatives, are widely regarded for their potential in ammonia decomposition for hydrogen production. However, their performance at low temperatures is suboptimal, necessitating the addition of promoters and a clear understanding of their mechanisms to enhance catalytic activity. In this study, we have successfully improved the low-temperature ammonia decomposition performance of Ni/CeO 2 by incorporating alkaline earth metals and conducted a comprehensive analysis of the underlying structural and electronic effects. The findings reveal that alkaline earth metals can enhance the basicity of the catalyst and increase electron density around the active metal sites, thereby facilitating the rate-determining step of recombination and desorption of N atom. Moreover, the presence of alkaline earth metals disrupts hydrogen adsorption stability on the catalysts, effectively mitigating the impact of hydrogen inhibition. Based on systematic kinetic experiments, a kinetic model was developed that accurately captures the hydrogen inhibition effect for Ni/CeO 2 catalysts. The insights into the promotional mechanisms of alkaline earth metals offer theoretical guidance for the development of highly active and cost-effective catalysts for ammonia decomposition.
Electrochemical CO 2 reduction (CO 2 RR) in acidic media circumvents carbonate crossover and salt precipitation inherent to alkaline and neutral systems, but suffers from low selectivity due to the dominance of hydrogen evolution. While alkali cations suppress proton activity, they inevitably lead to catastrophic (bi)carbonate deposition and electrode flooding. Here, we decouple CO 2 RR from alkali cations by constructing a micro-alkaline catalytic environment using a proton-blocking hydrophobic membrane with tethered cations. We designed a series of quaternized copolymers from dimethylaminoethyl methacrylate and lauryl methacrylate (qDMA-n), where the “cation–hydrophobicity balance” was precisely tuned to optimize the balance between Donnan exclusion and water management. Integrated into a zero-gap membrane electrode assembly electrolyzer, the optimized membrane enabled CO 2 RR on Ag catalysts with a CO faradaic efficiency of 96.9 % and a single-pass conversion efficiency of 92.4 % at 200 mA cm⁻ 2 in pure 0.05 M H 2 SO 4 , maintaining stable operation for over 100 h. Finite element simulations, rotating disk electrode tests and in-situ Raman spectra revealed that the balance between cationic and hydrophobic domains plays a key role in forming a stable micro-alkaline interface despite bulk acidity, leading to effective HER suppression. This work provides a practical and generalizable interface design principle for efficient CO 2 electrolysis in strong acids, offering new opportunities for durable, high-efficiency CO 2 electrolyzers without alkali cations.
Song Yun,Musgrave Charles B.,Su Jianjun,Huang Libei,Guo Weihua,Liu Yong,Li Geng,Xin Yinger,Zhang Qiang,Feng Xing,Liao Can,Liu Shunjie,Kwok Ryan Tsz Kin,Lam Jacky W. Y.,He Mingming,Choong Kai Shen,Feng Zhenxing,Tang Ben Zhong,Goddard William A.,Ye Ruquan
Electrosynthesis of value-added chemicals in strong acids can mitigate carbon loss and the operational cost of CO 2 reduction reaction (CO 2 RR). However, molecular catalysis for CO 2 RR is typically conducted in neutral or alkaline environments. CO 2 RR in acidic media is challenged by the scarcity of catalyst candidates, competitive hydrogen evolution and slow product formation. Here we report a locally ionic yet simultaneously hydrophobic and aerophilic layered structure that modulates the microenvironment surrounding cobalt phthalocyanine (CoPc) molecular catalysts, enabling efficient, multielectron CO 2 RR in acidic media. Experiment and theoretical modelling reveal that the polarized electrostatic field arising from the cationic groups suppresses hydronium migration. Concurrently, the van der Waals forces between the reactant gas and alkyl groups improve local CO availability, combining to achieve a methanol partial current density of 132 mA cm −2 with 62% selectivity at a pH of ~1 and –1.37 V RHE for CoPc, exceeding previous reports on neutral or alkaline electrolytes. The improved CO coverage also enables the detection of *CHO and *CO intermediates from in situ spectroscopy. We validate our strategy on various molecules, which champion the efficient inhibition of hydrogen evolution and improved CO 2 RR partial current density in acidic media. CoPc-based layered structure with similar ionic, hydrophobic and aerophilic interfaces also yields comparable methanol productivity.
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