The
present work reports a general approach to improve the electrocatalytic
property of noble metal through regulating its electron status by
introducing the electronic metal–support interaction (EMSI).
As a case study, the catalytic activity of metallic Pd toward oxygen
evolution reaction (OER) in alkaline solution has been significantly
promoted by stabilizing Pdδ+ oxidic species at the
interface of the Pd–metal oxide support with the help of EMSI
effect, suggesting an intrinsic advantage of Pdδ+ in driving OER. We further demonstrate that the chemical state of
Pdδ+ can be easily modulated in the range of 2+ to
3+ by changing the metal oxide support, interestingly, accompanied
by a clear dependence of the OER activity on the oxidation state of
Pdδ+. The high Pd3+ species-containing
Fe2O3/Pd catalyst has fed an impressively enhanced
OER property, showing an overpotential of 383 mV at 10 mA cm–2 compared to those of >600 mV on metallic Pd and 540 mV on Fe2O3/glassy carbon. The greatly enhanced OER performance
is believed to primarily derive from the distinctive improvement in
the adsorption of oxygenated intermediates (e.g., *OH and *OOH) on
metal-oxide/Pd catalysts. Moreover, similar EMSI induced improvements
in OER activity in alkaline solution are also achieved on both of
the Fe2O3/Au and Fe2O3/Pt, which possess the oxidic species of Au3+, and Pt2+ and Pt4+, respectively.
Creating active sites to improve the mass activity and durability
of metal catalysts by elucidating the relationship between the metal
and the support is a major challenge. In this study, ultrafine palladium
nanoparticles (Pd NPs) were supported on alkalized Ti3C2 (alk-Ti3C2) to obtain a catalytically
active interfacial ensemble. The catalyst Pd/alk-Ti3C2 with a Pd loading of 1.0 wt % exhibited the highest activity
in ammonia borane (AB) hydrolysis reaction, with an initial turnover
frequency of 230.6 min–1. A comprehensive analysis
revealed that an ensemble-exciting effect originated from the Pd and
the alk-Ti3C2. The hydroxylation of alk-Ti3C2 regulated the local coordination environment
of Pd. Water and AB were effortlessly activated by the −OH
group and Pd atom aggregates composed of electron-deficient support
alk-Ti3C2 and electron-rich Pd, respectively.
The efficient generation of hydrogen at the interface of Pd/alk-Ti3C2 was further guaranteed by the interfacial activation.
This work on precision active sites opens new avenues for developing
high-activity noble-metal catalysts for AB hydrolysis.
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