Optimizing Intermediate Adsorption via Heteroatom Ensemble Effect over RuFe Bimetallic Alloy for Enhanced Nitrate Electroreduction to Ammonia

Abstract

The electrochemical nitrate reduction reaction (NO3RR) is a promising approach for nitrate removal and NH3 synthesis at ambient conditions. As a complex eight‐electron/nine‐proton transfer process, its performance relies heavily on the adsorption ability of reaction intermediates on the catalyst surface, which is determined by the geometric and electronic configurations of active sites. In this work, a heteroatom ensemble effect is deliberately triggered over RuFe bimetallic alloy to optimize intermediate adsorption for NO3RR. A record‐high NH3 yield rate of 118.8 mg h−1 mg−1 and a high Faradaic efficiency of 92.2% are achieved at −1.4 V vs reversible hydrogen electrode, ranking at the top of the state‐of‐the‐art. Experimental and computational results reveal that the geometric and electronic characteristics of the induced heteroatom ensemble effect play crucial roles. Both Ru and Fe display a continuous state throughout the Fermi level, suggesting high electron density benefits the whole NO3RR. As a result, facilitated adsorption of NO3−, efficient stabilization of key intermediates, as well as the timely desorption of NH3 are simultaneously achieved, thus significantly promoting the direct reduction of NO3− to NH3.

Designing Efficient Nitrate Reduction Electrocatalysts by Identifying and Optimizing Active Sites of Co-Based Spinels

“…Accordingly, as shown in Figure d, O v slightly reduces the energy barrier of PDS from 0.76 to 0.55 eV, and meanwhile energy request associated with *NH 3 formation also becomes smaller. In addition, as it reported, the hydrogenation of *NO coverts to *HNO or *NOH during the process of NO 3 – RR . To this end, we also computed the reaction free energy of *NO hydrogenation to *HNO on Co Oh O 5 (Figure S34), and the reaction free energy for the generation of *HNO is 0.44 eV, smaller than *NOH (0.55 eV), indicating that the NO 3 – RR on Co Oh O 5 perfers the *HNO pathway.…”

“…In addition, as it reported, the hydrogenation of *NO coverts to *HNO or *NOH during the process of NO 3 − RR. 66 To this end, we also computed the reaction free energy of *NO hydrogenation to *HNO on Co Oh O 5 (Figure S34), and the reaction free energy for the generation of *HNO is 0. S35), suggesting that the NO 3 − RR can spontaneously occur at this potential, in consistence with our experimental results (Figure 1e).…”

The interface-mediated electron structure tuning of RuOx–Co3O4 nano-particles for efficient electrocatalytic nitrate reduction

“…9,11,22,23,34–37 Besides, the feasibility of utilizing various noble metals such as Ru, Ag, and Rh to catalyze NO 3 RR to generate ammonia has been verified. 15,38–43 Inspired by these facts, we designed and constructed a novel electrocatalyst, i.e. , RuO x –Co 3 O 4 nano-particles, with abundant interfaces by calcination and load it on carbon paper as an electrode for the efficient synthesis of ammonia.…”

Matched Kinetics Process Over Fe2O3‐Co/NiO Heterostructure Enables Highly Efficient Nitrate Electroreduction to Ammonia

“…In biological NO 3 − RR, this conversion involves a tandem reaction performed by a relay of distinct N‐reductases, where NO 3 − is first reduced to NO 2 − by nitrite reductases and then converted to NH 3 /N 2 by Fe‐ or Cu‐based nitrite reductases [8] . Based on enzymatic pathways, many researchers have constructed heterogeneous metal sites, such as atomically dispersed bimetallic catalysts, [9] alloys, [10] and metal oxides, [11] as active centers to achieve high NH 3 yields, where each metal site is tailored to selectively respond to a segment of the targeted reaction [12] . For instance, a Cu−Co binary metal sulfide catalyst shows a high NH 3 yield (1.17 mmol ⋅ h −1 ⋅ cm −2 ) with an FE of 93.3 %, where Cu sites efficiently reduce NO 3 − to NO 2 − and NO 2 − is selectively reduced to NH 3 over Co sites [13] .…”