${\text{La}}_2{\mathrm{NiO}}_4$ is an antiferromagnetic insulator with a structural resemblance to its cuprate counterpart, ${\mathrm{La}}_2{\mathrm{CuO}}_4$. However, ${\mathrm{La}}_2{\mathrm{CuO}}_4$ has a ${\mathrm{Cu}}^{2+}$ or $3d^9$ electronic configuration that needs to be hole or electron doped for superconductivity, whereas ${\mathrm{La}}_2{\mathrm{NiO}}_4$ is $3d^8$ with divalent ${\mathrm{Ni}}^{2+}$. Making a cuprate analog through conventional electron doping is impractical due to the rarity of tetravalent substituents for trivalent La. Here, we propose an alternative route: intercalating topotactical hydrogen, which is possible through electric-field-controlled protonation and transforms ${\mathrm{La}}_2{\mathrm{NiO}}_4$ into a $3d_{x^2-y^2}$ single-band two-dimensional antiferromagnetic Mott insulator analogous to ${\mathrm{La}}_2{\mathrm{CuO}}_4$. This we find through density-functional theory and dynamical mean-field theory calculations. The furthergoing dynamical vertex approximation predicts that $\mathrm{H}\text{−}{\mathrm{La}}_2{\mathrm{NiO}}_4$ can host $d$-wave superconductivity under 15% hole doping with a critical temperature above 20 K. Our findings not only suggest a new method for tuning the electronic structure of layered nickelates but also provide theoretical evidence for a new nickelate superconductor, awaiting experimental synthesis.

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• Superconductors
• d-wave
• Nickelates
• Strongly correlated systems
• Density functional theory
• Dynamical mean field theory
• First-principles calculations