Encouraged by the great promise of heteroatoms-doped carbon materials for catalyzing the oxygen reduction reaction (ORR) in fuel cells, phosphorus-doped carbon has exhibited high catalytic activity for the ORR. Here, by means of comprehensive density functional theory (DFT) computations, we explored the relationships among the catalytic activity, stability, and the local chemical bonding states at dopant sites of Pdoped graphene sheets for ORR to identify the most optimized P-doped graphene structure. The structures show that the P atom can substitute one or two C atoms to form P-doped graphene structures with three or four P−C bonds (PC3G or PC4G), respectively, and these structures are easily oxidized into the OPC3G and OPC4G models with P−O bond. The further calculations reveal that the stability, band structure, surface charge distribution, potential active sites, and free energy of the rate-determining step of P-doped graphene can be modulated effectively by the chemical bonding states of P atom and the formation of C−P−O bond. The OPC3G model is the most effective and stable P-doped graphene for ORR due to its stability, activity, and the amount of the potential active sites. Another significant finding is that the C atoms possessed high negative charge, which also can be the optimal active sites for ORR. Our work provides useful guidance for the rational design and fabrication of P-doped graphene framework and helpful further activity enhancement.

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Slow kinetics of the hydrogen oxidation reaction (HOR) in alkaline electrolyte impedes the development of alkaline fuel cell systems. In this work, density functional theory calculations were used to study the HOR mechanism on several metals (Pt(110), Ir(110), Pd(110), Ni(110), and PtRu(110)), particularly by additionally considering the adsorption of hydroxyl species (OH*) on these metals. We found that the formation of OH* can transfer the potential-determining step of HOR mechanism from the H* oxidation to H 2 O* desorption under remarkably different effects of OH* on H* and H 2 O*. The comprehensive Δ r G−U relational diagrams for HOR/hydrogen evolution reaction show that, apart from the widely accepted activity descriptor, H* adsorption free energy (ΔG H* ), OH* adsorption free energy (ΔG OH* ), and H 2 O* adsorption free energy (ΔG H 2 O* ) also should be involved in predicting the HOR catalytic activity of metal catalysts in alkaline electrolyte. When the OH* formation free energy change (Δ r G OH* = ΔG OH* , at equilibrium potential) is more positive than the H* oxidation free energy change (Δ r G H*→H 2 O* = ΔG H 2 O* − ΔG H* , at equilibrium potential), ΔG H* as the sole descriptor indicates the HOR activity of catalysts due to scarce formation of OH* and a relatively weak H 2 O* adsorption at a relatively low overpotential, which happened in the case of Pt(110) and Pd(110). When Δ r G OH* and Δ r G H*→H 2 O* have little difference as in the case of Ir(110), both OH* formation and H* oxidation affect of the HOR and ΔG OH* and the enhanced ΔG H 2 O* by OH* should be involved in evaluating the HOR activity. In the case of Ni(110), a much lower value of Δ r G OH* than that of Δ r G H*→H 2 O* causes the surface to be mostly blocked by OH*, which suppresses the HOR. The combination of ΔG OH* , ΔG H* , and ΔG H 2 O* gives a more precise and comprehensive description of the HOR mechanism for metallic catalysts at different electrode potentials.

Macroporous CoFeP triangular plate arrays constructed from MOFs as high-performance overall water-splitting catalysts.