Higher Water‐Splitting Performance of Boron‐Based Porous CoMnB Electrocatalyst over the Benchmarks at High Current in 1 m KOH and Real Sea Water

Abstract

emission nature, the hydrogen is receiving significant attentions as a renewable energy alternative. [2,3] The electrocatalytic water splitting, consisted of the half-reaction of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), is an appealing approach for the generation of ultra-fine hydrogen with the zero-carbon emission nature and recyclability as compared with the other hydrogen generation approaches of gasification, gas reforming, renewable liquid reforming, etc. [4] To date, the Pt/Pd and IrO 2 /RuO 2 set the benchmark electrocatalysts for the HER and OER with the low overpotentials due to their excellent water-splitting capabilities. Nevertheless, their high costs make the large-scale implementation of hydrogen generation pricier and thus the development of highly efficient and stable electrocatalysts at affordable costs still remains to be one of the major challenges for the comprehensive application of green hydrogen production by the electrochemical water splitting (WS). The transition metal-based electrocatalysts with the d-orbital characteristics, i.e., Co, Ni, Cu, Fe, Mo, W, Mn, Cr, etc., have been widely explored as the electrolytic electrode alternatives with the superb HER and OER reaction capabilities and abundance on the earth crust. [5][6][7][8] The transition metals have been frequently compounded with the nonmetallic phosphide, sulfide, nitride, etc., and significant advances have been made along with the outstanding WS performances due to their superb intrinsic HER/OER reaction capabilities. [9][10][11][12] Meantime, the Co and Mn have demonstrated outstanding electron transportability and absorption of hydrogen protons and hydroxyl species. [9][10][11][12] For instance, the CoNi-MOF exhibited a low overpotential due the rapid electron transfer rate facilitated by the adequate Co incorporation. [9] The Mn-doped Ni 2 P microflowers demonstrated a low cell voltage due to the improved conductivity and increased electrochemical active sites by the incorporation of Mn. [10] The combination of Co and Mn with the nonmetallic elements of methylidyne and selenide groups such as CoMnCH and CoMnSe has demonstrated improved intrinsic characteristics for the WS. [11,12] More recently, the boron (B) is being considered as another useful nonmetallic element for The development of highly efficient and stable electrocatalysts at an affordable cost is an essential component for the large-scale implementation of green hydrogen production. In this work, the fabrication of porous CoMnB electrocatalyst is demonstrated with the incorporation of boron into the Co-Mn matrix by an electrochemical approach for bifunctional water electrocatalysis for the first time. The optimized CoMnB electrocatalyst demonstrates an excellent bifunctionality with a low 2-E turnover voltage of 1.59 V at 20 mA cm −2 in 1 m KOH. The CoMnB shows a comparable water-splitting current at low current range as compared with the standard benchmark electrodes of Pt/C||RuO 2 in 1 m KOH. Then, the CoMnB outperforms the benchm...

Exploring the Role of Multi-Catalytic Sites in an Amorphous Co–W–B Electrocatalyst for Hydrogen and Oxygen Evolution Reactions

“…The experimental results establish the promising bifunctional performance of the Co–W–B catalyst, highlighting the significant role of W incorporation in Co–B. Indeed, there are few studies supporting the fact that the incorporation of a second metal in binary borides enhances their electrocatalytic rates. ,, However, to the best of our knowledge, there are not many studies focused on the identification of true catalytic sites in such complex amorphous systems, such as ATMBs. This is partly due to the limitations in experimental identification of the true catalytic sites, as often argued in the community .…”

“…Indeed, there are few studies supporting the fact that the incorporation of a second metal in binary borides enhances their electrocatalytic rates. 23,24,50 However, to the best of our knowledge, there are not many studies focused on the identification of true catalytic sites in such complex amorphous systems, such as ATMBs. This is partly due to the limitations in experimental Figure 4a−d represents the top few atomic layers of optimized Co−W−B structure with W at different sites, namely, W@Co/B, W@Co, W@B, and W-direct (see Methods for description of each site).…”

Boron/Nitrogen-Induced Surface Environment Modulation for Favorable Phase and Valence toward Efficient Oxygen Evolution

“…For B (Figure 2f) and N (Figure 2g) XPS spectra, there are three types of bonding states as formed by coupling with Mo, O, or C, namely, B/N−Mo, B/N−O, and B/N−C. 34,35 Specifically, the bonding between B/N and Mo is identified at low binding energies while the interaction between B/N and O occurs at high energies. 36,37 Electrocatalytic OER performance of the resultant BMOtype and NMO-type catalysts was evaluated in 1.0 M KOH solution.…”

“…Despite that, no obvious signal of Mo is detected for the BMO-950 catalyst by using the XPS technique, the element mapping patterns derived from SEM characterization verifies the presence of trace Mo species (Figure S9). For B (Figure f) and N (Figure g) XPS spectra, there are three types of bonding states as formed by coupling with Mo, O, or C, namely, B/N–Mo, B/N–O, and B/N–C. , Specifically, the bonding between B/N and Mo is identified at low binding energies while the interaction between B/N and O occurs at high energies. , …”

Impact of Highly Concentrated Alkaline Treatment on Mesostructured Cobalt Oxide for the Oxygen Evolution Reaction

“…[4] Further, the commercial reagent grade KOH pellet mostly only contains circa 85% of KOH; hence, the presence of impurities could be prominent on the electrocatalyst and the reaction when the concentrated KOH solution is used as an electrolyte.Cobalt oxide spinel is one of the most studied electrocatalysts for oxygen evolution reaction (OER) in the recent decade owing to its tunable morphology and electronic structure. [5][6][7][8][9][10][11][12][13][14][15] However, the spinel phase is not the real catalyst for OER since its surface undertakes a transformation into an oxyhydroxide intermediate active state upon the anodic polarization. [9,16] This phase transformation might take place only at several or subnanometers regions of the catalyst surface, within the vicinity of electrode and electrolyte interfaces.…”