Heterogeneous Bimetallic Phosphide/Sulfide Nanocomposite for Efficient Solar-Energy-Driven Overall Water Splitting

Abstract

Solar-driven overall water splitting is highly desirable for hydrogen generation with sustainable energy sources, which need efficient, earth-abundant, robust, and bifunctional electrocatalysts for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Herein, we propose a heterogeneous bimetallic phosphide/sulfide nanocomposite electrocatalyst of NiFeSP on nickel foam (NiFeSP/NF), which shows superior electrocatalytic activity of low overpotentials of 91 mV at -10 mA cm for HER and of 240 mV at 50 mA cm for OER in 1 M KOH solution. In addition, the NiFeSP/NF presents excellent overall water splitting performance with a cell voltage as low as 1.58 V at a current density of 10 mA cm. Combining with a photovoltaic device of a Si solar cell or integrating into photoelectrochemical (PEC) systems, the bifunctional NiFeSP/NF electrocatalyst implements unassisted solar-driven water splitting with a solar-to-hydrogen conversion efficiency of ∼9.2% and significantly enhanced PEC performance, respectively.

Cobalt Phosphides Nanocrystals Encapsulated by P‐Doped Carbon and Married with P‐Doped Graphene for Overall Water Splitting

“…The CoP-Co 2 P@ PC/PG||CoP-Co 2 P@PC/PG device (Figure 5A) only requires a cell voltage of 1.567 V to drive the OWS to reach a current density of 10 mA cm −2 , superior to Pt/C||IrO 2 pair (1.576 V) and their pure-phase counterparts based devices ( Figure S21, Supporting Information). Also, the OWS activity of CoP-Co 2 P@PC/PG NHs is better than other reported bifunctional catalysts, such as Cu 0.3 Co 2.7 P/NC (1.620 V for 10 mA cm −2 ), [15] FeCoP nanosheets (1.600 V for 10 mA cm −2 ), [22] NiFeSP/NF (1.580 V for 10 mA cm −2 ), [32] Ni 1−x Fe x PS 3 @MXene (1.650 V for 10 mA cm −2 ), [33] NiCo 2 S 4 NW/NF(1.630 V for 10 mA cm −2 ), [34] and so on. The detailed comparison of OWS activity of CoP-Co 2 P@PC/PG NHs with other reported catalysts is provided in Table S3 (Supporting Information).…”

Multifunctional Transition Metal‐Based Phosphides in Energy‐Related Electrocatalysis

“…In this regard, Zhang and co-workers used the hexagonal NiS (0001) as the pristine model and investigated the effect of dual doping Fe and P on their electronic structure via DFT calculations. [98] As demonstrated in Figure 5a, the replacement of one topmost surface Ni/S atom by Fe and P atoms could generate the NiFeS (Figure 5a Figure 5a-a5, a6), respectively. The results revealed that the P atom preferred to be doped on the inner layer sites while the Fe doping would cause segregation of the inner P to the surface.…”

“…In common, the cations and anions dual‐doping can engender dual synergetic effects on modulating adsorption energy, electrical conductivity, etc. In this regard, Zhang and co‐workers used the hexagonal NiS (0001) as the pristine model and investigated the effect of dual doping Fe and P on their electronic structure via DFT calculations . As demonstrated in Figure 5 a, the replacement of one topmost surface Ni/S atom by Fe and P atoms could generate the NiFeS (Figure a‐a3) and NiSP (Figure a‐a4), and NiFeSP (Figure a‐a5, a6), respectively.…”

“…b) Comparison of free energies for HER on Pt, NiFeSP, NiFeS, NiSP, NiS, and Ni 2 P catalysts. Reproduced with permission . Copyright 2017, American Chemical Society.…”

“…Energy Mater. 2020, 10,1902104 [98] Copyright 2017, American Chemical Society. c) Calculated values of the turnover frequency on CoO, CoPO, and CoFePO for HER and OER.…”