Enhanced Electrocatalysis for Energy‐Efficient Hydrogen Production over CoP Catalyst with Nonelectroactive Zn as a Promoter

Abstract

As a non‐toxic species, Zn fulfills a multitude of biological roles, but its promoting effect on electrocatalysis has been rarely explored. Herein, the theoretic predications and experimental investigations that nonelectroactive Zn behaves as an effective promoter for CoP‐catalyzed hydrogen evolution reaction (HER) in both acidic and alkaline media is reported. Density function theory calculations reveal that Zn doing leads to more thermal‐neutral hydrogen adsorption free energy and thus enhanced HER activity for CoP catalyst. Electrochemical tests show that a Zn0.08Co0.92P nanowall array on titanium mesh (Zn0.08Co0.92P/TM) needs overpotentials of only 39 and 67 mV to drive a geometrical catalytic current of 10 mA cm‐2 in 0.5 m H2SO4 and 1.0 m KOH, respectively. This Zn0.08Co0.92P/TM is also superior in activity over CoP/TM for urea oxidation reaction (UOR), driving 115 mA cm‐2 at 0.6 V in 1.0 m KOH with 0.5 m urea. The high HER and UOR activity of this bifunctional electrode enables a Zn0.08Co0.92P/TM‐based two‐electrode electrolyzer for energy‐saving hydrogen production, offering 10 mA cm‐2 at a low voltage of 1.38 V with strong long‐term electrochemical stability.

Single‐Atom to Single‐Atom Grafting of Pt1 onto FeN4 Center: Pt1@FeNC Multifunctional Electrocatalyst with Significantly Enhanced Properties

“…The Gibbs free-energy of H adsorption (ΔG H* ) on the catalyst has been commonly used to evaluate its HER activity, with ΔG H* value more close to zero implying a faster charge transfer for both H* intermediate and H 2 formation. [42,43] Strikingly, Pt 1 @FeNC shows a very low ΔG H* value of 0.16 eV, which is comparable to 0.09 eV of Pt/C(20%), better than 0.24 eV of Pt 1 @C and much better than 0.65 eV of FeNC (Figure 4d). Figure S23 and Table S6, Supporting Information show the patterns and corresponding structural parameters of Pt 1 @FeNC and FeNC for H* adsorption analysis.…”

Tungsten‐Doped CoP Nanoneedle Arrays Grown on Carbon Cloth as Efficient Bifunctional Electrocatalysts for Overall Water Splitting

“…[11] Transition metal phosphides (TMPs), such as cobalt phosphides (CoP) have been investigated as HER catalysts due to the high catalytic activity and durability [12] and CoP has also demonstrated promising OER catalytic properties in basic electrolytes, although the real active species are surface oxy/hydroxide formed in situ under the oxidative conditions in OER. [14] However, ΔG H* on the (101) surface of CoP is calculated to be À 0.36 eV [15] which causes larger overpotentials for HER, generally higher than 100 mV at a current density of 10 mA cm À 2 in an alkaline electrolyte. The HER activity is correlated with hydrogen adsorption free energy (ΔG H* ) on the catalyst surface and the optimal HER activity is achieved at a thermoneutral ΔG H* of 0 eV.…”

“…[13] Therefore, TMPs, particularly CoP, should be promising low-cost and high-performance HER and OER bifunctional catalysts for overall water-splitting. [15][16] For example, Sun et al improved the ΔG H* on the (101) surface of CoP from À 0.36 to À 0.08 eV by Zn doping and the overpotential is decreased from 99 to 67 mV at a current density of 10 mA cm À 2 in 1 M KOH. [14] However, ΔG H* on the (101) surface of CoP is calculated to be À 0.36 eV [15] which causes larger overpotentials for HER, generally higher than 100 mV at a current density of 10 mA cm À 2 in an alkaline electrolyte.…”

“…[14] However, ΔG H* on the (101) surface of CoP is calculated to be À 0.36 eV [15] which causes larger overpotentials for HER, generally higher than 100 mV at a current density of 10 mA cm À 2 in an alkaline electrolyte. [17] In spite of recent improvements in the HER and OER performance of CoP, [15,[17][18] highly active and durable CoP-based bifunctional electrocatalysts suitable for both HER and OER in the same electrolyte for overall water splitting have rarely been reported. [15][16] For example, Sun et al improved the ΔG H* on the (101) surface of CoP from À 0.36 to À 0.08 eV by Zn doping and the overpotential is decreased from 99 to 67 mV at a current density of 10 mA cm À 2 in 1 M KOH.…”

Cobalt-vanadium bimetal-based nanoplates for efficient overall water splitting

“…The materials based on early and late transition metals (ETMs and LTMs) are promising for HER and OER [14,15], such as the transition metals sulfides [16,17], phosphides [18][19][20][21][22], selenide [23], nitride [24][25][26] and carbides [27] for HER, and oxides (Ni oxides [28,29] and Co oxides [30][31][32]) for OER. The cobalt (Co), as a typical LTM, is promising in HER due to its relatively low cost and the activity for the reduction of H + [33].…”