Interface engineering and heterometal doping Mo-NiS/Ni(OH)2 for overall water splitting

Abstract

Developing cost-effective, efficient and bifunctional electrocatalysts is vital for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) application. The catalytic activity of electrocatalysts could be optimized by reasonable electronic structure regulation and increasing active sites. Herein, we report the design and fabrication of Mo-doped nickel sulfide/hydroxide heterostructures (Mo-NiS/Ni(OH) 2 ) as a multisite water splitting catalyst via straightforward solvothermal and in-situ growth strategy. Based on foreign metal doping and interface interaction, the electronic conductivity of heterostructures is improved and the charge transfer kinetics across the interface is promoted, which are demonstrated by the theoretical calculations. Mo-NiS/Ni(OH) 2 electrocatalyst is endowed with high electrocatalytic performance for water splitting and remarkable durability in alkaline electrolyte. It exhibits the low overpotential of 186 and 74 mV at 10 mA•cm −2 for OER and HER, respectively. Importantly, after continuously working for 50 h, the current densities of HER and OER both show negligible degeneration. Even, the resulting Mo-NiS/Ni(OH) 2 better catalyzes water splitting, yielding a current density of 10 mA•cm −2 at a cell voltage of 1.5 V and outperforming Pt/C-IrO 2 couple (1.53 V). This result demonstrates that transition metal doping and heterogeneous interface engineering are useful means for conventional catalyst design.

Vanadium-Doping and Interface Engineering for Synergistically Enhanced Electrochemical Overall Water Splitting and Urea Electrolysis

“…Both are higher than 120 mV dec –1 , implying that the water dissociation on these two electrocatalysts is slow, and therefore, the Volmer step serves as the rate-determining step. The Tafel values of V-FeNi 3 N/Ni 3 N (108.2 mV dec –1 ) and V-Ni 3 N (65.3 mV dec –1 ) are between 40 and 120 mV dec –1 , indicating that both of them follow the Volmer–Heyrovsky mechanism . Accordingly, the electrochemical desorption of H 2 is believed to be the rate-determining step .…”

“…The Tafel values of V-FeNi 3 N/Ni 3 N (108.2 mV dec −1 ) and V-Ni 3 N (65.3 mV dec −1 ) are between 40 and 120 mV dec −1 , indicating that both of them follow the Volmer−Heyrovsky mechanism. 69 Accordingly, the electrochemical desorption of H 2 is believed to be the ratedetermining step. 70 The abovementioned results suggest that V-doping can accelerate the water dissociation kinetics of Ni 3 N and FeNi 3 N/Ni 3 N and trigger the transition of the ratedetermining step from Volmer to Heyrovsky steps.…”

Atmospheric‐Temperature Chain Reaction towards Ultrathin Non‐Crystal‐Phase Construction for Highly Efficient Water Splitting

“…Amorphous Fe(OH) 3 on catalysts with appropriate thickness can improve the contact between the catalyst and electrolyte, promoting nano‐interface exposure for improved catalytical activity. [ 11c,d,15b,17c,d] …”

“…LSV curve after 2000/5000 consecutive CV scans were same as the original one (Figure 5e) and I−T cure owned basically constant current with 10 mA cm −2 during 35 h electrolysis (Figure 5f), indicating excellent durability of CCH−FeOH−D2 || CCH−FeOH−D2 electrolyzer. All the data evidence CCH−FeOH is a competent bifunctional electrocatalyst towards full water splitting, which may be attributed to the advantages of high surface‐volume ratio and synergistic multi‐functionalization of the components [17b] as well as the strong interaction between Fe and Co at the crystal‐amorphous interface, [11c] thus improving the conductivity enhancing charge separation/transport and facilitating electron transfer in the reaction [31]…”

Hollow Mo-doped NiSx nanoarrays decorated with NiFe layered double-hydroxides for efficient and stable overall water splitting

“…22 Among the various metal cationic dopants, Mo is a common n-type dopant to increase the free electron concentration in the active materials; besides that, Mo doping has been evidenced to improve the electrical conductivity and stability of host materials. 23 Therefore, Mo is expected as an ideal dopant in electrode materials for improving the electrochemical properties. Although heteroatom doping is a powerful means to increase the electrocatalytic activity, it is difficult to achieve satisfactory results just by the introduction of foreign atoms for overall water splitting.…”