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PRINCIPAL PUBLICATION AND AUTHORS

The role of Ni in PtNi bimetallic electrocatalysts for hydrogen and value-added chemicals co-production via glycerol electrooxidation, H. Luo (a), V.Y. Yukuhiro (b), P.S. Fernández (b), J. Feng (a,c), P. Thompson (d), R.R. Rao (a), R. Cai (e), S. Favero (a), S.J. Haigh (e), J.R. Durrant (a), I.E.L. Stephens (a), M.M. Titirici (a,f), ACS Catal. 12, 23, 14492-14506 (2022); https:/doi.org/10.1021/acscatal.2c03907 (a) Imperial College London (UK) (b) State University of Campinas (Brazil) (c) Queen Mary University of London (UK) (d) XMaS/BM28, ESRF (e) University of Manchester (UK) (f) Tohoku University (Japan)

REFERENCES

[1] H. Luo et al., Adv. Energy. Mater. 11, 2101180 (2021). [2] R.R. Rao et al., J. Am. Chem. Soc. 144, 17, 7622 (2022).

increasing partial current density towards glycolate (through C-C bond cleavage) observed in Figure 79b, it is proposed that higher Ni content in PtNi can also significantly promote the partial C-C bond cleavage towards glycolate formation. These results demonstrate that Ni plays a significant role in PtNi s performance towards GEOR.

By combining operando XANES with online UV-Vis spectroscopy [2], it was observed that Ni gets poisoned by glycerol entirely, which explains why transition metal oxides and hydroxides in contrast to platinum group metals need excessive overpotentials to oxidise glycerol, under which conditions C-C scission is favoured, yielding low value products such as formate and carbonate (Figure 79c). This observation ruled out the hypothesis of bifunctional effect and suggested that Ni s role in modulating *CO and *OH binding energy on the Pt sites is

induced by strain and ligand effects. With in-situ infrared spectroscopy, it was further proved that adding more Ni reduces the barrier to the partial C−C cleavage and hence increases selectivity toward glycolate and formate.

In summary, the role of Ni in PtNi catalysts for GEOR is schematically illustrated in Figure 79d: the surface Ni atoms form Ni(OH)x islands in alkaline conditions and get poisoned by glycerol molecules, blocking the sites for *OH adsorption and thus ruling out the possibility of a bifunctional mechanism. Instead, the presence of Ni modulates the electronic structure of surface Pt atoms, weakening the *CO and *OH binding energy. The Pt−Ni structure in PtNi2 induces the most optimised *CO and *OH adsorption strength on Pt sites, thereby displaying the highest activity in this study. Such fundamental insights into the GEOR paves the way for catalyst design for selective electrochemical alcohol oxidation.

Fig. 79: a) Mass and specific activity comparisons of PtNi catalysts. b) Partial current density for glycolate, derived from Faradaic efficiency based on equation Jp = Jtotal x FE%. c) Overview of the functionality of different electrocatalysts from the literature and

present work. Left: Current density in alkaline media, right: Faradaic selectivity towards C3 products. d) Illustration of the electronic effect in PtNi electrocatalysts (green: Ni, grey: Pt) under potential <1VRHE.