RESUMO
Amorphization of the support in single-atom catalysts is a less researched concept for promoting catalytic kinetics through modulating the metal-support interaction (MSI). We modeled single-atom ruthenium (RuSAs ) supported on amorphous cobalt/nickel (oxy)hydroxide (Ru-a-CoNi) to explore the favorable MSI between RuSAs and the amorphous skeleton for the alkaline hydrogen evolution reaction (HER). Differing from the usual crystal counterpart (Ru-c-CoNi), the electrons on RuSAs are facilitated to exchange among local configurations (Ru-O-Co/Ni) of Ru-a-CoNi since the flexibly amorphous configuration induces the possible d-d electron transfer and medium-to-long range p-π orbital coupling, further intensifying the MSI. This embodies Ru-a-CoNi with enhanced water dissociation, alleviated oxophilicity, and rapid hydrogen migration, which results in superior durability and HER activity of Ru-a-CoNi, wherein only 15â mV can deliver 10â mA cm-2 , significantly lower than the 58â mV required by Ru-c-CoNi.
RESUMO
It remains a great challenge to explore high-performance electrocatalysts for the CO2 reduction reaction (CO2RR) with high activity and selectivity. Herein, we employ first principles calculations to systematically investigate an emerging family of extended surface catalysts, bi-atom catalysts (BACs), in which bimetals anchored on graphitic carbon nitride (g-CN), for the CO2RR; and propose a novel framework to boost the CO2RR via incorporation with well-defined clusters. Among 28 BACs, five candidates (Cr2, CrFe, Mn2, MnFe and Fe2/g-CN) are first selected with efficient CO2 activation and favorability for CO2 reduction over H2 evolution. Fe2@g-CN is then served as a superior electrocatalyst for the CO2RR with low limiting potentials (UL) of -0.58 and -0.54 V towards C1 and C2 products. Intriguingly, the CO2RR performance of pure Fe2@g-CN could be controlled by tunable Fe atomic cluster integration. In particular, the presence of an Fe13 cluster could strengthen the CO2 adsorption, effectively deactivate H, and intriguingly break the adsorbate (CO* and CHO*) scaling relation to achieve the distinguished CO2RR with a lowered UL to -0.45 V for the C1 mechanism, which is attributed to the exceptional charge redistribution of bimetals modulated by Fe13. Our findings might open up possibilities for the rational design of BACs towards the CO2RR and other reactions.
RESUMO
Single-atom-catalysts (SACs) afford a fascinating activity with respect to other nanomaterials for hydrogen evolution reaction (HER), yet the simplicity of single-atom center limits its further modification and utilization. Obtaining bimetallic single-atom-dimer (SAD) structures can reform the electronic structure of SACs with added atomic-level synergistic effect, further improving HER kinetics beyond SACs. However, the synthesis and identification of such SAD structure remains conceptually challenging. Herein, systematic first-principle screening reveals that the synergistic interaction at the NiCo-SAD atomic interface can upshift the d-band center, thereby, facilitate rapid water-dissociation and optimal proton adsorption, accelerating alkaline/acidic HER kinetics. Inspired by theoretical predictions, we develop a facile strategy to obtain NiCo-SAD on N-doped carbon (NiCo-SAD-NC) via in-situ trapping of metal ions followed by pyrolysis with precisely controlled N-moieties. X-ray absorption spectroscopy indicates the emergence of Ni-Co coordination at the atomic-level. The obtained NiCo-SAD-NC exhibits exceptional pH-universal HER-activity, demanding only 54.7 and 61 mV overpotentials at -10 mA cm-2 in acidic and alkaline media, respectively. This work provides a facile synthetic strategy for SAD catalysts and sheds light on the fundamentals of structure-activity relationships for future applications.