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Engineering surface atomic structure of single-crystal cobalt (II) oxide nanorods for superior electrocatalysis

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ABSTRACT

Engineering the surface structure at the atomic level can be used to precisely and effectively manipulate the reactivity and durability of catalysts. Here we report tuning of the atomic structure of one-dimensional single-crystal cobalt (II) oxide (CoO) nanorods by creating oxygen vacancies on pyramidal nanofacets. These CoO nanorods exhibit superior catalytic activity and durability towards oxygen reduction/evolution reactions. The combined experimental studies, microscopic and spectroscopic characterization, and density functional theory calculations reveal that the origins of the electrochemical activity of single-crystal CoO nanorods are in the oxygen vacancies that can be readily created on the oxygen-terminated {111} nanofacets, which favourably affect the electronic structure of CoO, assuring a rapid charge transfer and optimal adsorption energies for intermediates of oxygen reduction/evolution reactions. These results show that the surface atomic structure engineering is important for the fabrication of efficient and durable electrocatalysts.

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Bifunctional ORR/OER performance of SC CoO NRs.(a) ORR linear-sweep voltammograms (LSVs) of SC, PC CoO NRs and Pt catalysts directly deposited on CFP in O2-saturated 1 M KOH solution at scan rate of 0.5 mV s−1 without iR correction, with ORR chronoamperometric response to methanol addition shown in inset. (b) ORR Tafel plots of SC, PC CoO NRs and Pt catalysts. (c) ORR chronoamperometric response of SC CoO NRs and Pt catalysts at a constant voltage of 0.60 VRHE. (d) OER LSVs of SC, PC CoO NRs and commercial RuO2 catalysts directly deposited on CFP in O2-saturated 1 M KOH solution at scan rate of 0.5 mV s−1 without iR correction, with the corresponding OER Tafel plots shown in inset.
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f4: Bifunctional ORR/OER performance of SC CoO NRs.(a) ORR linear-sweep voltammograms (LSVs) of SC, PC CoO NRs and Pt catalysts directly deposited on CFP in O2-saturated 1 M KOH solution at scan rate of 0.5 mV s−1 without iR correction, with ORR chronoamperometric response to methanol addition shown in inset. (b) ORR Tafel plots of SC, PC CoO NRs and Pt catalysts. (c) ORR chronoamperometric response of SC CoO NRs and Pt catalysts at a constant voltage of 0.60 VRHE. (d) OER LSVs of SC, PC CoO NRs and commercial RuO2 catalysts directly deposited on CFP in O2-saturated 1 M KOH solution at scan rate of 0.5 mV s−1 without iR correction, with the corresponding OER Tafel plots shown in inset.

Mentions: As-fabricated SC CoO NRs with length of 1.6 μm on CFP were directly used as the working electrodes for both ORR and OER (Supplementary Fig. 9), and their performances were compared with analogous electrodes prepared by using PC CoO NRs (Supplementary Fig. 10), the state-of-art Pt and RuO2 catalysts supported on CFP. The polarization curves were recorded without iR correction. As regards ORR (Fig. 4a,b and Supplementary Fig. 11a), PC CoO NRs exhibit low activity, while SC CoO NRs show an onset potential of 0.96 V versus reversible hydrogen electrode (VRHE), a half-wave potential (E1/2) of 0.85 VRHE and a Tafel slope of 47 mV per decade, which approach the values measured for Pt catalysts. These values are better than those of the well-developed cobalt oxide nanocrystals (NCs) coupled with carbon materials (Supplementary Table 2). Moreover, SC CoO NRs show high selectivity towards ORR with strong methanol tolerance (Fig. 4a, inset). Besides an extraordinary activity towards ORR, SC CoO NRs also demonstrate an excellent durability. As shown in Fig. 4c, SC CoO NRs retain 97% of the initial ORR current after 10 h continuous testing, whereas Pt catalyst lost more than 26% of its initial current, confirming much better durability of active reaction sites present on SC CoO NRs (Supplementary Figs 12 and Supplementary Fig. 13). Moreover, even after 3,000 cycle catalytic tests with accelerated scan rate of 100 mV s−1, SC CoO NRs still retained their structure (Supplementary Fig. 14). This excellent durability originates from direct growth of SC CoO NRs on the CFP substrate to avoid aggregating and detaching problems, which are usually encountered in other faceted catalysts49.


Engineering surface atomic structure of single-crystal cobalt (II) oxide nanorods for superior electrocatalysis
Bifunctional ORR/OER performance of SC CoO NRs.(a) ORR linear-sweep voltammograms (LSVs) of SC, PC CoO NRs and Pt catalysts directly deposited on CFP in O2-saturated 1 M KOH solution at scan rate of 0.5 mV s−1 without iR correction, with ORR chronoamperometric response to methanol addition shown in inset. (b) ORR Tafel plots of SC, PC CoO NRs and Pt catalysts. (c) ORR chronoamperometric response of SC CoO NRs and Pt catalysts at a constant voltage of 0.60 VRHE. (d) OER LSVs of SC, PC CoO NRs and commercial RuO2 catalysts directly deposited on CFP in O2-saturated 1 M KOH solution at scan rate of 0.5 mV s−1 without iR correction, with the corresponding OER Tafel plots shown in inset.
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f4: Bifunctional ORR/OER performance of SC CoO NRs.(a) ORR linear-sweep voltammograms (LSVs) of SC, PC CoO NRs and Pt catalysts directly deposited on CFP in O2-saturated 1 M KOH solution at scan rate of 0.5 mV s−1 without iR correction, with ORR chronoamperometric response to methanol addition shown in inset. (b) ORR Tafel plots of SC, PC CoO NRs and Pt catalysts. (c) ORR chronoamperometric response of SC CoO NRs and Pt catalysts at a constant voltage of 0.60 VRHE. (d) OER LSVs of SC, PC CoO NRs and commercial RuO2 catalysts directly deposited on CFP in O2-saturated 1 M KOH solution at scan rate of 0.5 mV s−1 without iR correction, with the corresponding OER Tafel plots shown in inset.
Mentions: As-fabricated SC CoO NRs with length of 1.6 μm on CFP were directly used as the working electrodes for both ORR and OER (Supplementary Fig. 9), and their performances were compared with analogous electrodes prepared by using PC CoO NRs (Supplementary Fig. 10), the state-of-art Pt and RuO2 catalysts supported on CFP. The polarization curves were recorded without iR correction. As regards ORR (Fig. 4a,b and Supplementary Fig. 11a), PC CoO NRs exhibit low activity, while SC CoO NRs show an onset potential of 0.96 V versus reversible hydrogen electrode (VRHE), a half-wave potential (E1/2) of 0.85 VRHE and a Tafel slope of 47 mV per decade, which approach the values measured for Pt catalysts. These values are better than those of the well-developed cobalt oxide nanocrystals (NCs) coupled with carbon materials (Supplementary Table 2). Moreover, SC CoO NRs show high selectivity towards ORR with strong methanol tolerance (Fig. 4a, inset). Besides an extraordinary activity towards ORR, SC CoO NRs also demonstrate an excellent durability. As shown in Fig. 4c, SC CoO NRs retain 97% of the initial ORR current after 10 h continuous testing, whereas Pt catalyst lost more than 26% of its initial current, confirming much better durability of active reaction sites present on SC CoO NRs (Supplementary Figs 12 and Supplementary Fig. 13). Moreover, even after 3,000 cycle catalytic tests with accelerated scan rate of 100 mV s−1, SC CoO NRs still retained their structure (Supplementary Fig. 14). This excellent durability originates from direct growth of SC CoO NRs on the CFP substrate to avoid aggregating and detaching problems, which are usually encountered in other faceted catalysts49.

View Article: PubMed Central - PubMed

ABSTRACT

Engineering the surface structure at the atomic level can be used to precisely and effectively manipulate the reactivity and durability of catalysts. Here we report tuning of the atomic structure of one-dimensional single-crystal cobalt (II) oxide (CoO) nanorods by creating oxygen vacancies on pyramidal nanofacets. These CoO nanorods exhibit superior catalytic activity and durability towards oxygen reduction/evolution reactions. The combined experimental studies, microscopic and spectroscopic characterization, and density functional theory calculations reveal that the origins of the electrochemical activity of single-crystal CoO nanorods are in the oxygen vacancies that can be readily created on the oxygen-terminated {111} nanofacets, which favourably affect the electronic structure of CoO, assuring a rapid charge transfer and optimal adsorption energies for intermediates of oxygen reduction/evolution reactions. These results show that the surface atomic structure engineering is important for the fabrication of efficient and durable electrocatalysts.

No MeSH data available.


Related in: MedlinePlus