Perhaps you could try to chroot again:
sudo mount /dev/sda5 /mnt
sudo mount /dev/sda1 /mnt/boot/efi
sudo arch-chroot /mnt
Inside chroot, try reinstalling your kernels:
pacman -Syu linux linux-headers (for example for the latest stable)
This should trigger mkinitcpio automatically.
Check under /boot directory to see if the kernel images and the initramfs are present.
For good measure, reinstall the bootloader and regenerate your grub.cfg:
grub-install
grub-mkconfig -o /boot/grub/grub.cfg
When done, type exit followed by enter to quit chroot.
Reboot.