Tailoring the Electronic Structure of Co₂P by N Doping for Boosting Hydrogen Evolution Reaction at All pH Values

Abstract

The development of precious-metal-free electrocatalysts with high-efficiency for hydrogen evolution reaction (HER) at all pHs is of great interest for the development of electrochemical overall splitting technologies. Despite that intense efforts have been made to developing cost-effective electrocatalysts toward HER under both acidic and alkaline electrolytes with high efficiency, electrocatalysts with remarkable performance in neutral media are rare. Herein, N atoms doped Co2P nanorod arrays grown on carbon cloth (N–Co2P/CC) have been successfully synthesized and further used as efficient electrocatalysts for HER at all pH values. Specially, the N–Co2P/CC exhibits an overpotential of 42 mV at the current density of 10 mA cm –2 with long-term stability in 1.0 M PBS (phosphate-buffered solution), which is comparable to the benchmark Pt/CC. Density functional theory (DFT) calculations suggest nitrogen doping could tailor the electronic structure of Co2P, leading to optimized adsorption free energies of water (ΔG *H2O) and hydrogen (ΔG *H), facilitating hydrogen generation through the Volmer–Heyrovsky mechanism.

Hierarchically Porous W‐Doped CoP Nanoflake Arrays as Highly Efficient and Stable Electrocatalyst for pH‐Universal Hydrogen Evolution

“…The Nyquist plots (Figure S8a–c, Supporting Information) obtained in the three electrolytes can be fitted to the equivalent circuits (the insets). After fitting the Nyquist plots, the electron transfer resistance ( R ct ) values of W‐CoP NAs/CC are identified to be 4.2 Ω (0.5 m H 2 SO 4 ), 5.1 Ω (1.0 m KOH), and 7.4 Ω (1.0 m PBS), which are much lower than those of CoP NAs/CC (11.3, 12.5, and 20.3 Ω) and Co 3 O 4 NAs/CC (348.5, 292.7, and 495.6 Ω), indicating its fastest interfacial electron transfer kinetics at all pH values during the HER process …”

“…Nonetheless, the electrocatalytic performances of TMPs‐based materials cannot fully meet the requirement of practical applications, due to the relatively slow charge transportation and lack of exposed active sites . What is more, most of the reported TMPs‐based catalysts are only beneficial in acidic or alkaline media and still require large overpotentials to reach the current density of 10 mA cm −2 for practical application, especially in neutral electrolyte . Hence, it is greatly significant and desirable to develop high‐efficient and stable TMPs‐based HER electrocatalysts in pH‐universal electrolytes.…”

“…In recent years, heteroatom doping has demonstrated as one of most effective ways to enhance the intrinsic catalytic activity of TMPs by modulating their electronic conductivity and electronic structures . For example, Sun and coworkers presented that Mn‐doped Ni 2 P nanosheets show enhanced HER performance in alkaline electrolyte, which is due to the Mn doping can remarkably improve the electronic conductivity of Ni 2 P. Lu et al reported that Ni‐doped FeP/C hollow nanorods show improved catalytic activity in pH‐universal electrolytes.…”

Chemical Doped Ternary and Quaternary Transition‐Metal‐Based Electrocatalysts for Hydrogen Evolution Reaction

“…After N‐doping, the ΔG H values for CoP with various exposed crystal planes became more positive and thereby thermal‐neutral, which corresponded to the downshifted d‐band center for N‐doped CoP and facilitated HER (Figure e and 7f). The electronic structure regulation of Co 2 P by N‐doping were further reported for realizing highly‐efficient HER in neutral media (Figure g) . DFT calculations were utilized by authors to get deep understanding on the mechanism of the enhanced performance.…”

Synergism of Interface and Electronic Effects: Bifunctional N‐Doped Ni3S2/N‐Doped MoS2 Hetero‐Nanowires for Efficient Electrocatalytic Overall Water Splitting

“…Among various structures, 1D hetero‐nanowires have been demonstrated to be superior for gas‐involving electrocatalysis; this is mainly attributed to their abundant, well‐exposed active sites; efficient charge transfer; and unique surface properties for gas evolution and release . Apart from structure engineering, regulating the composition of electrocatalysts by heteroatom doping is another alternative strategy to boost the catalytic activity . Of particular interest is the nitrogen anion dopant, which has demonstrated its utility for modifying the functionalities and properties of transition‐metal‐based electrocatalysts.…”