A considerable amount of platinum (Pt) is required to ensure an adequate rate for the oxygen reduction reaction (ORR) in fuel cells and metal‐air batteries. Thus, the implementation of atomic Pt ...catalysts holds promise for minimizing the Pt content. In this contribution, atomic Pt sites with nitrogen (N) and phosphorus (P) co‐coordination on a carbon matrix (PtNPC) are conceptually predicted and experimentally developed to alter the d‐band center of Pt, thereby promoting the intrinsic ORR activity. PtNPC with a record‐low Pt content (≈0.026 wt %) consequently shows a benchmark‐comparable activity for ORR with an onset of 1.0 VRHE and half‐wave potential of 0.85 VRHE. It also features a high stability in 15 000‐cycle tests and a superior turnover frequency of 6.80 s−1 at 0.9 VRHE. Damjanovic kinetics analysis reveals a tuned ORR kinetics of PtNPC from a mixed 2/4‐electron to a predominately 4‐electron route. It is discovered that coordinated P species significantly shifts d‐band center of Pt atoms, accounting for the exceptional performance of PtNPC.
Phosphorus‐coordinated atomic Pt‐Nx sites are theoretically predicted and experimentally realized, offering enhanced kinetics for four‐electron electrochemical oxygen reduction. Exceptional activity is attributed to the tuning of the d‐band electron center via local coordination asymmetry. This chemistry provides an effective guideline for atomic Pt catalysts in batteries and fuel cells.
Producing indispensable hydrogen and oxygen for social development via water electrolysis shows more prospects than other technologies. Although electrocatalysts have been explored for centuries, a ...universal activity descriptor for both hydrogen‐evolution reaction (HER) and oxygen‐evolution reaction (OER) is not yet developed. Moreover, a unifying concept is not yet established to simultaneously understand HER/OER mechanisms. Here, the relationships between HER/OER activities in three common electrolytes and over ten representative material properties on 12 3d‐metal‐based model oxides are rationally bridged through statistical methodologies. The orbital charge‐transfer energy (Δ) can serve as an ideal universal descriptor, where a neither too large nor too small Δ (≈1 eV) with optimal electron‐cloud density around Fermi level affords the best activities, fulfilling Sabatier's principle. Systematic experiments and computations unravel that pristine oxide with Δ ≈ 1 eV possesses metal‐like high‐valence configurations and active lattice‐oxygen sites to help adsorb key protons in HER and induce lattice‐oxygen participation in the OER, respectively. After reactions, partially generated metals in the HER and high‐valence hydroxides in the OER dominate proton adsorption and couple with pristine lattice‐oxygen activation, respectively. These can be successfully rationalized by the unifying orbital charge‐transfer theory. This work provides the foundation of rational material design and mechanism understanding for many potential applications.
A universal activity descriptor (orbital charge‐transfer energy) is successfully extracted from various materials’ physicochemical properties for both hydrogen‐evolving and oxygen‐evolving reactions in multiple electrolytes. Systematic experiments and computations reveal the life‐cycle HER and OER mechanisms and identify the unifying orbital charge‐transfer theory as a powerful mechanism analysis tool and foundation.
Abstract
CO
2
hydrogenation has attracted great attention, yet the quest for highly-efficient catalysts is driven by the current disadvantages of poor activity, low selectivity, and ambiguous ...structure-performance relationship. We demonstrate here that C
3
N
4
-supported Cu single atom catalysts with tailored coordination structures, namely, Cu–N
4
and Cu–N
3
, can serve as highly selective and active catalysts for CO
2
hydrogenation at low temperature. The modulation of the coordination structure of Cu single atom is readily realized by simply altering the treatment parameters. Further investigations reveal that Cu–N
4
favors CO
2
hydrogenation to form CH
3
OH via the formate pathway, while Cu–N
3
tends to catalyze CO
2
hydrogenation to produce CO via the reverse water-gas-shift (RWGS) pathway. Significantly, the CH
3
OH productivity and selectivity reach 4.2 mmol g
–1
h
–1
and 95.5%, respectively, for Cu–N
4
single atom catalyst. We anticipate this work will promote the fundamental researches on the structure-performance relationship of catalysts.
Development of robust catalysts for electrochemical water splitting is a critical topic for the energy conversion field. Herein, a precise electrochemical reconstruction of IrTe2 hollow nanoshuttles ...(HNSs) is performed for oxygen and hydrogen evolution reactions (OER and HER), the two half reactions of water splitting. It is determined that the reconstruction of IrTe2 HNSs can be regulated by adjusting the potential during electrochemical dealloying, in which mild and high potentials lead to the formation of IrTe2 HNSs with metal Ir shell (D‐IrTe2 HNSs) and IrOx surface (DO‐IrTe2 HNSs), respectively. Detailed analyses reveal that such electrochemical reconstruction has produced abundant defects in D‐IrTe2 and DO‐IrTe2 HNSs. As a result of this, D‐IrTe2 HNSs present a very low HER overpotential of 54 mV at a current density of 10 mA cm−2 in 1.0 m KOH. Moreover, the turnover frequency of DO‐IrTe2 HNSs is 0.36 O2 s−1 at an OER overpotential of 250 mV in 0.5 m H2SO4, outperforming the most of reported Ir‐based catalysts. Furthermore, the D‐IrTe2||DO‐IrTe2 couple exhibits promising activity for the overall water splitting in both 1.0 m KOH and 0.5 m H2SO4. This study promotes the fundamental research for the design of efficient catalysts via surface engineering.
Surface‐modulated iridium tellurides are fabricated via precise electrochemical reconstruction as efficient and pH‐universal electrocatalysts for water splitting.
Replacing the anodic oxygen evolution reaction (OER) with a thermodynamically favorable ethanol oxidation reaction (EOR) is regarded as a promising approach to simultaneously realize energy‐saving H2 ...evolution and high‐value chemical production. Herein, the single‐atom In‐doped subnanometer Pt nanowires (SA In‐Pt NWs) as high‐performance electrocatalysts for both the hydrogen evolution reaction (HER) and EOR under universal pH conditions is designed. The SA In‐Pt NWs/C can be employed to integrate HER with EOR to avoid the large overpotential caused by sluggish OER, which requires a smaller voltage of 0.62 V to reach 10 mA cm–2 compared with that of water splitting (2.07 V). The reaction also exhibits a high faradaic efficiency of over 93% in upgrading ethanol to valuable acetate in the anodic cell. Mechanistic investigations indicate that the combination of the ultrathin 1D morphology and single‐atom In decoration provides the maximum number of active sites and effectively activates Pt atoms for catalysis. Density functional theory calculations further demonstrate that doped In can effectively promote the HER, while also promoting the conversion of ethanol to acetate. Moreover, through the use of SA In‐Pt NWs/C as electrocatalysts, many other alcohols can also be employed as anodic feedstock to achieve coupled electrolysis.
Single‐atom In‐doped subnanometer Pt nanowires are successfully developed as an advanced class of high‐performance electrocatalysts for simultaneous energy‐saving H2 generation and biomass upgrading, thus revealing their advantages in addressing the energy and environmental crisis.
The rational fabrication of Pt‐free catalysts for driving the development of practical applications in alkaline water electrolysis and fuel cells is promising but challenging. Herein, a promising ...approach is outlined for the rational design of multimetallic catalysts comprising multiple active sites including Pd nanoclusters and Ru single atoms anchored at the defective sites of Ni(OH)2 to simultaneously enhance hydrogen evolution reactions (HER) and ethanol oxidation reactions (EOR). Remarkably, Pd12Ru3/Ni(OH)2/C exhibits a remarkably reduced HER overpotential (16.1 mV@10 mA cm−2 with a Tafel slope of 21.8 mV dec−1) as compared to commercial 20 wt.% Pt/C (26.0 mV@10 mA cm−2, 32.5 mV dec−1). More importantly, Pd12Ru3/Ni(OH)2/C possesses a self‐optimized overpotential to 12.5 mV@10 mA cm−2 after 20 000 cycles stability test while a significantly decreased performance for commercial 20wt.% Pt/C (64.5 mV@10 mA cm−2 after 5000 cycles). The mass activity of Pd12Ru3/Ni(OH)2/C for the EOR is up to 3.724 A mgPdRu−1, ≈20 times higher than that of commercial Pd/C. Electrochemical in situ Fourier transform infrared measurements confirm the enhanced CO2 selectivity of Pd12Ru3/Ni(OH)2/C while synergistic and electronic effects of adjacent Ru, Pd, and OHad adsorption on Ni(OH)2 at low potential play a key role during EOR.
The Pd12Ru3/Ni(OH)2/C catalyst with the novel nanostructure of Pd nanoclusters and Ru single atoms anchored at the defective sites of Ni(OH)2 is designed and prepared, enhancing its catalytic performance for hydrogen evolution reaction and ethanol electrocatalytic oxidation reactions due to the synergistic and electronic effect of Ni(OH)2, Ru single atoms and Pd clusters.
Two‐dimensional (2D) metal–organic framework nanosheets (MOF NSs) play a vital role in catalysis, but the most preparation is ultrasonication or solvothermal. Herein, a liquid–liquid interfacial ...synthesis method has been developed for the efficient fabrication of a series of 2D Ni MOF NSs. The active sites could be modulated by readily tuning the ratios of metal precursors and organic linkers (RM/L). The Ni MOF NSs display highly RM/L dependent activities towards 2e oxygen reduction reaction (ORR) to hydrogen peroxide (H2O2), where the Ni MOF NSs with the RM/L of 6 exhibit the optimal near‐zero overpotential, ca. 98 % H2O2 selectivity and production rate of ca. 80 mmol gcat−1 h−1 in 0.1 M KOH. As evidenced by X‐ray absorption fine structure spectroscopy, the coordination environment of active sites changed from saturation to unsaturation, and the partially unsaturated metal atoms are crucial to create optimal sites for enhancing the electrocatalysis.
2D Ni metal–organic framework nanosheets (MOF NSs) with controlled coordination mode were carefully created through a liquid‐liquid interfacial synthesis strategy for the first time and adopted as efficient electrocatalysts for hydrogen peroxide (H2O2) synthesis. The optimized partially unsaturated Ni MOF NSs‐6 exhibits near‐zero overpotential as well as ca. 98 % H2O2 selectivity in 0.1 M KOH, exceeding most electrocatalysts up to date.
Shape control has realized huge success for developing efficient Pd/Pt‐based nanocatalysts, but the control of Ru‐based nanocrystals remains a formidable challenge due to the inherent anisotropy in ...hexagonal closed‐packed nanocrystals. Herein, a class of unique RuCo nanoscrews (NSs) for water electrosplitting is successfully synthesized with rough surfaces and the exposure of steps and edges. Those high‐index faceted RuCo NSs show superior performance for overall water electrosplitting, where a low cell voltage of 1.524 V (@ 10 mA cm−2) and excellent stability for more than 20 h (@ 10 mA cm−2) for overall water electrosplitting in 1 m KOH is achieved. The enhanced performance of RuCo NSs is due to the optimization of the binding energy with the intermediate species and the reduced energy barrier of water dissociation. Density functional theory calculations reveal that the RuCo NS structure intrinsically endows various ridges and edges, which create low coordinated Ru‐ and Co‐sites. These active Ru‐ and Co‐sites present high efficiencies in electronic exchange and transfer between adsorbing O species and nearby lattice sites, guaranteeing the high H2O‐splitting activities. This present work opens up a new strategy for creating high‐performance electrocatalysts for water splitting.
A RuCo electrocatalyst with abundant high index facets is successfully fabricated with superior performance for water‐splitting in an alkaline environment, which is attributed to the simultaneous facilitation of both an alloying effect and high‐index facets. This work supplies significant insights for future research to further overcome the challenge of realizing bimetallic electrocatalysts with high‐index facets.
Corner‐sharing oxides usually suffer from structural reconstruction during the bottleneck oxygen‐evolution reaction (OER) in water electrolysis. Therefore, introducing dynamically stable active sites ...in an alternative structure is urgent but challenging. Here, 1D 5H‐polytype Ba5Bi0.25Co3.75FeO14−δ oxide with face‐sharing motifs is identified as a highly active and stable candidate for alkaline OER. Benefiting from the stable face‐sharing motifs with three couples of combined bonds, Ba5Bi0.25Co3.75FeO14−δ can maintain its local structures even under high OER potentials as evidenced by fast operando spectroscopy, contributing to a negligible performance degradation over 110 h. Besides, the higher Co valence and smaller orbital bandgap in Ba5Bi0.25Co3.75FeO14−δ endow it with a much better electron transport ability than its corner‐sharing counterpart, leading to a distinctly reduced overpotential of 308 mV at 10 mA cm−2 in 0.1 m KOH. Further mechanism studies show that the short distance between lattice‐oxygen sites in face‐sharing Ba5Bi0.25Co3.75FeO14−δ can accelerate the deprotonation step (*OOH + OH− = *OO + H2O + e−) via a steric inductive effect to promote lattice‐oxygen participation. In this work, not only is a new 1D face‐sharing oxide with impressive OER performance discovered, but also a rational design of dynamic stable and active sites for sustainable energy systems is inaugurated.
The 1D 5H‐polytype Ba5Bi0.25Co3.75FeO14−δ oxide with high‐valence face‐sharing motifs is developed as a highly efficient and stable electrocatalyst for oxygen‐evolving reaction. This exceptional face‐sharing structure can be maintained even under high anodic potentials and accelerates the deprotonation step (*OOH + OH− = *OO + H2O + e−) via a steric inductive effect to promote lattice‐oxygen participation.
Single‐atom catalysts (SACs) have shown great potential in the electrochemical oxygen reduction reaction (ORR) toward hydrogen peroxide (H2O2) production. However, current studies are mainly focused ...on 3d transition‐metal SACs, and very little attention has been paid to 5d SACs. Here, a new kind of W SAC anchored on a porous O, N‐doped carbon nanosheet (W1/NO‐C) is designed and prepared via a simple coordination polymer‐pyrolysis method. A unique local structure of W SAC, terdentate W1N1O2 with the coordination of two O atoms and one N atom, is identified by the combination of aberration‐corrected scanning transmission electron microscopy, X‐ray photoelectron spectroscopy and X‐ray absorption fine structure spectroscopy. Remarkably, the as‐prepared W1/NO‐C catalyzes the ORR via a 2e– pathway with high onset potential, high H2O2 selectivity in the wide potential range, and excellent operation durability in 0.1 m KOH solution, superior to most of state‐of‐the‐art H2O2 electrocatalysts ever reported. Theoretical calculations reveal that the C atoms adjacent to O in the W1N1O2‐C moiety are the most active sites for the 2e– ORR to H2O2 with the optimal binding energy of the HOO* intermediate. This work opens up a new opportunity for the development of high‐performance W‐based catalysts for electrochemical H2O2 production.
A new kind of tungsten single atom catalyst anchored on a porous O, N‐doped carbon nanosheet (W1/NO‐C) is reported as an exceptional 2e– ORR electrocatalyst for H2O2 electrosynthesis, which originates from a unique terdentate W1N1O2 structure with the coordination of two O atoms and one N atom as demonstrated by the combined experimental analysis and theoretical calculations.
PDF
